Öncel akademİ: environmental geophysics
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1974-IU Jeofizik Binasinda bir ders sonrasi1984-Kandilli Rasathanesi Paleomanyetizma Laboratuvari
ITU Jeofizik Muhendisligi Ogretim Uyeleri ve Ogrenciler-1982?
1989-Istanbul Paleozoyik kayaclari uzerinde paleomanyetik calisma icin Houston, Teksasa yolculuk
1-Houston Universitesi:1989-1990 Istanbul Paleozoik kayaclari uzerine arastirma2-Bir petrol sirketinde jeoteknik eleman: 1990-1991Karadenizin olusumu uzerine paleomanyetik seminer;Gravite ve Manyetik petrol verisi degerlendirme;Amerika Jeofizik Dernegi yillik toplantisina katilma;Florida Universitesinde Doktora-ustu calisma teklifi 3-Bir cevre sirketinde jeofizikci: 1991-19934-Kendi Cevre Jeofizigi sirketimi kurma: 1994Yogun bir sekilde herseyi yeniden ogrenme temposu;Nasil iyi bir danisman, is adami olunur?Nasil iyi bir insan olunur?Sorular, sorular ve aranan yanitlar!
Dogal Uclasma-Alf HawkinsManyetik ve Iletimlilik-Kerlon Saravia Alf HawkinsKerlon Saravia
Isci Bulma Kurumunun buldugu iki isci
Definition of Geophysics
.
Geophysics is: The subsurface site characterization of the geology, geological structure, groundwater, contamination, and human artifacts beneath the Earth's surface, based on the lateral and vertical mapping of physical property variations that are remotely sensed using non-invasive technologies.
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3 boyutlu Yer Radari haritasi3 boyutlu Ozdirenc haritasiMoistCevre Jeofizigi Urunleri
A Resistivity Survey and Data: Purpose is to locate a metallic source near metallic sheets at a refinery X
EM34 Method Conductivity map of brine plume at 30 feet below surface in groundwater. The brine leaked from an injection well and affected the groundwater forming a plume (pink, red and yellow colors.
Enjeksiyon kuyusu
There are thousands, oil and gas wells that are buried in the ground across Texas, and their locations are unknown. A magnetic survey is the primary method to uncover their locations.
GPR with 400 MHz antennaYeralti depoloma tanklarini Yer Radari ile bulma
Seismic refraction tomography across a fault A normal fault with a ~35 feet throw at about South Gate DepthFeetGeorgetownGeorgetownEdwards Aquifer
Definition of Anomaly in Dictionary -Belirti A deviation from the background, type, arrangement, or form.
23
24Geophysics:Continuous Data Coverage Results in Better Control in Geology Borehole:Discreet SamplingGeophysical Results Should Guide Where Borehole Locations Should Be Placed
Fourteen Geophysical Techniques
Geophysical Solutions to a Foundation Problem, Houston
Patio-VerandaGarageWood deckNorthern backyardLets get to know the House!
VoidPictures from Veranda
Pictures from northern backyardVoidExcavated soft, moist soil
Pictures from living room and garage
A picture from wood deck
GL1GL2GL3Locations of GPR profiles at the Veranda
WE0 5 10 15 20 25 Ft FtSubsidenceAnomalyVoid under the patio GPR profile along GL1
WE 0 5 10 15 20 25 FtFtSurface GPR Profile GL2-No significant anomaly!
Locations of GPR profiles at Wood Deck area
GL7GL8 0 5 10 15 20 Ft WestEastFtFtArtifact anomalyNo significant anomaly!
GL9Location of GPR profiles at the Garage
WestEast0 5 10 15 20 25 Ft FtRebar in concreteThere were significant cracks on the floor of the garage but the GPR data did not show any subsurface deformation
GL10GL11GL12Location of GPR profiles inside the house
0 5 10 15 20 25 30 Ft Bathroom doorGL10GL11GPR profiles along GL10 and 11No significant deformation!
GL13Location of GPR profile GL13Excavatedarea
0 5 10 15 20 25 30 35 40 45 Ft WestEastFt
Excavated areaSubsidence areaGPR anomaly
A significant GPR anomaly-Note that we did not see any similar anomaly at other areas of the house
A B
Location of the resistivity profile at the northern backyard: 28 electrode (elektrot), 1 metre elektrot araligiElectrode 1
ABNatural Potential Survey: A) Base station; B) Roving electrode
WestEastClayClaySilty sand SandSand, silty sand
Excavated area next to the houseSand
Resistivity DataNP DatamVFeetNP anomalyNP anomaly?Metal gate
6 ft (2 m)Excavated area showing the voidWhat is the source of the void; what did it cause?
GPR anomalyWhat could be the source of geophysical anomalies?
GPR, resistivity and NP anomaly
The GPR data obtained from the Patio, wood deck and garage do NOT indicate any significant anomalies.However, the GPR data collected from the northern side of the house does indicate subsidence and presence of soft, wet soil as deep as 6 feet. These anomalous features correspond to precisely where the excavated soil is piled up and where we observed the deformation of the foundation.In addition, the resistivity data show a significant subsidence anomaly associated with sand and clay layers in the same area. The NP data shows a low NP anomaly between the same stations where GPR and resistivity anomalies observed, and thus complements the above interpretation. The source of the NP anomaly is probably due to moving water into the ground.
Conclusions:
GPR anomalyWhere could it be the source of geophysical anomalies?
GPR, resistivity and NP anomaly
Main Barton Geophysics: Where is all the water coming from into the Barton Springs Pool?!Main BartonMustafa Saribudak Environmental Geophysics Associates(EGA)Austin, Texaswww.egatx.com
UD
51
Hurricane Ike- Summer 2008Benim ev
Swim in constantly 68-degrees, spring-fed Barton Springs
4th largest spring system in Texas Water temperature: 68F (22C) Mean discharge: 53 cfs (105 acre-feet/day)
Anatomy of Barton Springs Pool 4th largest spring system in Texas Water temperature: 68F (22C) D U
Geological Cross-section of Barton SpringsSWNE
Key karstic features to explore and identify over Barton Springs with geophysicsGroundwater flow paths? What is the geophysical signature of the BS Fault?What type of karstic features are there in the vicinity of Barton Springs Pool?How deep are they?
UDGeorgetownEdwards Aquifer110 my100 myGeorgetown formation consists of limestone mixed with marlEdwards Aquifer is mostly limestone
Integrated Geophysical Methods Used in this StudyConductivityResistivityInduced Polarization*Natural Potential (NP)Ground Penetrating Radar (GPR)Seismic Refraction
*Induksiyon polarizasyonu
58
Groundwater Flow Routes toward Barton Springs Pool based on Dye Tracing-Boya Izleme
Barton Springs
Dye Tracing-Boya Izleme
Main Barton
South Gate Resistivity, seismic refraction, resistivity, induced polarization, and natural potential lines across the Barton Springs FaultRSI R2UDFlow
M. Well
Line R1Two resistivity profiles across Barton Springs Fault. E d w a r d s A q u i f e r Georgetown
E d w a r d s A q u i f e rLine R2LINE R2Georgetown
MW
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E d w a r d s A q u i f e rGeorgetownG. Water level
Monitoring wellInduced polarization and resistivity data across the Barton Springs Fault
NWSE Barton Springs Fault
GeorgetownFeetEdwards AquiferNWSEmVABNP gradientNatural Potential and induced polarization Data across the Fault
Velocity(ft/sec)Seismic refraction tomography profile along BS Fault NWSEGeorgetownEdwards Aq.
Summary of Geophysical Data across the BS Fault:
Resistivity, seismic refraction and induced polarization data map the fault well;
The natural potential data does not show any significant anomaly across the fault;
The NP data does not indicate any significant karstic feature and strong groundwater flow across the fault. Wait for the next set of geophysical data to justify this interpretation!
Main Barton
Location of Natural Potential Profile at Barton Springs Pool
South GateUD
MWN1
Endangered Salamanders (Semender) of Barton Springs
Utilizes the earths natural-electric field at the ground surface to detect and map groundwater pathways and geologic features, such as faults, fractures, conduits, caves
Movement of waterSeepage, Voids Natural-Potential Method (NP)
NP Base Station
NP Roving Staff
WE mVNP Data at the Barton Springs PoolFeetBS FaultA significant NP anomalyNP anomaly
72
N
Superimposing the NP Data over aerial view of Barton Springs PoolMain Barton
South GateUD
Main Barton
Locations of NP and Resistivity Profiles at Barton Springs L1*L2L3L4L5
*Conductivity, seismic refraction, and GPR surveys were also collected along L1.
South GateSpacing between lines was 50 feetNP anomaly
FeetEM31 Conductivity Data along Line 1
South Gate locationWestEast South GateEdited conductivity data indicates two rocks type with two significantly conductivity values across the south gate:
Is there a fault?
75
GPR data along Line 1The GPR data indicates a fault-type anomaly
WestEast
South Gate Resistivity Imaging Data-Line 1
P E C A N T R E E S
Line 1-NP DataFeetmVNP anomalyResistivity anomaly
Correlation of resistivity and induced polarization data along the same profile Induced polarization
GateWEHere is an enigmatic IP result: 181 mS value where low resistivity anomaly is located
Seismic Refraction Survey in front of the South Gate in Zilker Park Line 1 View to east
Seismic refraction tomography data along Line 2DepthFeetGeorgetownGeorgetownSeismic Refraction Tomography DataEdwards Aq.Georgetown formation consists of limestone mixed with marlEdwards Aquifer is mostly limestone
NPmVSeismic refraction tomography
WESouth Gate Resistivity
Seismic refraction tomography
NP
Road
Line 2NP Data-Line 3 WEFeet mVNP anomaly
Line 2Line 3
WE
Resistivity profiles 4 and 5
50 ft (16m)
N3D Resistivity Data in the E-W DirectionConduitConduit: Iletimlilik zonu?
Main Barton Locations of N-S NP and Resistivity Profiles at Barton Springs L6 L7 L8 L9 L10
UD
NFrom W to E:L6,7,8,9,10
L4
L5
L7L8L9L10NSS. GateNo significant anomaly on L9 profile L7R e s i s t i v i t y a n o m a l y
Resistivity and NP data on Line 6 on a dry day!
mV Feet
NSNP data NP anomalyNP data
NSFeet mVResistivity and NP data on Line 8 after a Stormy Day! NP a n o m a l y
NP Data along Line 8 on a dry day
NP Data Line 8 after a big storm
mV
N 3D Resistivity Data of N-S Lines
Main Barton
Location of a newly discovered Georgetown outcrop in the vicinity of the Barton Springs Pool!
Location of Georgetown outcrop
UDSouth GateUD
Cross-bedded gravelGravel
10 FeetLocation of newly found George town outcrop near the PoollGeorgetown Formation
Main Barton
Location of a newly discovered Georgetown outcrop in the vicinity of the Barton Springs Pool!
Location of Georgetown outcrop
UDSouth GateUD
Abundant Georgetown borehole data~1000 ft
UDMWBarton Springs Fault
UD
455444460
451453424
422
420
419
431
423
Locations of geophysical anomalies and top elevations of Georgetown Formation based on the borehole, monitoring well, outcrop and geophysical data
BoreholeGeophysical, MW, and outcrop
Yes, Geophysics is the way to go!
And the reward was a free swim in the pool!
Integrated geophysical investigations of Main Barton Springs, Austin, Texas, USA 1 2 By Mustafa Saribudak, Nico M. Hauwert This second paper is in review in Journal of Geophysics
Spring, TexasDont Mess with a Geophysicists House: A Case Study of Ground Penetrating Radar for Concrete Moisture Mapping and Void Detection in the Saturated Soil beneath the Concrete Foundation The House
Spring, Texas, 2008The House Mustafa Saribudak-Environmental Geophysics Associates
Site History:
We moved into a new house, The carpet is removed due to an allergy and replaced by wood , 6 months later , the wood floor showed color changes, A plumber company visited twice but found no leaks, An engineering company visited and found high moisture values on the living room, A structural engineer from the home-builder company found no evidence of damage in the foundation,
But the wood floor kept getting darker and darker.
Dont you have a GPR company? I am leaving this house until you find a solution!
Ground Penetrating Radar (GPR)
GPR maps dielectric contrast: It is the ability to hold electrical currentConcrete: 5-9Clay: 12-35Water: 81Air: 1Depth Exploration: Depends on the conductivity of the soil
100
How GPR Does Work?
2510181811
11
EX-1EX-2EX-3Decayed wood floor in the living room!
Moisture readings10Known post-tension cables
Concrete PatioF/P
Excavations3D GPR survey area
Post-tension cables embedded in the concrete foundation Living room with wood flooring
EX-1EX-2EX-3 GPR SURVEY DESIGN
N GPR survey with 1500 MHz antenna1500 MHz data was collected with a 15 cm profile spacing
LowHighAmplitude Scale
Concrete bottom 3D GPR 1500 MHz DATA FROM CONCRETE FOUNDATION Post-tension cablesVoidBottom of concreteLow
25
10
N GPR Survey Cart with 400 MHz AntennaGPR data was collected with one-foot profile spacing and depth of exploration was about 6 feet
Excavated VoidEX-2 EX-1
N
Low High
AmplitudeFigure 6EX-3 3D GPR DATA for 400 MHz Antenna: 3 ft depth slice
EX-1 EX-2N
EX-3 Low HighAmplitude 3D GPR Data for antenna 400 MHz: 5 Ft depth sliceEX-1
EX-3 Void
October 8, 2008October 28, 2008
Water depth is four inch
Water depth is one inch Excavated void at EX-3 location based on the GPR data. A three- foot long stick was pushed into the void with little resistance.Hurricane Ike hit Houston in September 12, 2008
Site History Continued:
An engineer from the home-builder company revisited the foundation and told us that our grace period was over, and no compensation was due, Our insurance company, whose slogan was we are on your side, was no longer on our side,So we put a french drainage around the house and replaced the dead wood floor with a ceramic tile; and moved to another house.
EX-3The story continues..
The new house was around the same area
The House
And few months later, a collapse occurred in Drive Way
Subsidence
Remarks The GPR is obviously the only proper method that can provide excellent results over any kind of foundation problems whether they are residential or business buildings. However, whenever necessary, GPR surveys should be associated with micro-resistivity and NP surveys for foundation problems..
114
GEOPHYSICAL METHODS FOR VOID AVOIDANCEON A TRANSMISSION LINE PROJECTMustafa Saribudak Environmental Geophysics Associates
Overview of Geophysical TechniquesBorehole:DiscreteSamplingGeophysics:Continuous DataCoverage Results inBetter Control of Geology
Geophysical ResultsShould Guide WhereBorehole LocationsShould Be Placed
Problems addressed by geophysical methods
118
Geophysical equipment used
ResistivityGPR
Natural Potential
119
Electrical Resistivity ImagingRock/Material Type Resistivity Range (m)
Igneous100 - 1000000Limestone100 - 10000Sandstone100 - 1000Sand and gravel600 - 10000Clay10 - 100Unconsolidated wet clay20Soil1 - 10Fresh water3 - 100VOID 1000-10000
120
Detecting Minerals /Mining
GPR and its ApplicationsThis method works on only 5% of the earths surface! When it works it is the best! The quality of the data depends on the dielectric contrast of the intended target with the surrounding material Dielectric Constant:Air 1Water 81Limestone 5-10Clay 14-24Sand 4
Natural Potential Method
The Natural Potential Method utilizes the earths natural-electric field at the ground surface to detect and map groundwater pathways and geologic features. Typical applications include: Detecting caverns and tunnels Siting monitoring wells and water-supply wells Locating leaks in dams, ponds and reservoirs Identifying hazards in landfill planning
122
Cave Entrance
Resistivity Data
miliVolt
Cave EntranceNP Data
Cave EntranceGPR DATA
Cave Detection With Resistivity Method
Entrance to Trench Cave
125
Trench Cave 2-D Resistivity Imaging
Trench Cave Entrance
Cave Entrance
NP DataTrench Cave Entrance
126
49 56 63 70 77 81 84 Ft Ft
Subsidence
Observed Cave LocationGPR data at Trench Cave
60 100 150 200 250 300 Ft
Cave Entrance
Known Cave
0 50 100 150 200 250 Ft Cave Entrance C A V E
Known Fault
Resistivity data near a known major fault and across a cave
0 5 10 15 20 Ft NWSE
CaveCaveCave GPR Data showing cave adjacent to major fault 0 5 10 15 20Limestone FT
Karst feature surveys were conducted prior to preliminarytransmission line structure locating.Transmission Line Void Avoidanceon Conservation Lands
A narrow swath was clearedfor access and geophysical surveys
Structure A.Resistivity data along Structure A
Structure A
Karst anomalyNatural Potential Data along Structure A
50 55 60 65 70 75 80 Feet
FtStructure AGPR Data along Structure A
Structure A.Resistivity data along Structure A and location of borehole
BoreholeI heavily relied on the resistivity data and ignored the NP anomaly and did not relocate the location of Structure A
Core drilling 9 m deep to test structure site suitabilityStructure locations were adjusted based on Geophysical SurveysStructure A
Microvoids
Geovision downhole camera equipment
Lowering downhole camera
Fracture and minor void at 7.3 m depth, structure D, not significant
Lateral view of cave passage, 5.2 m depth, structure AThis hole blew moist air
Downhole camera covered with cave mud
Lateral view of cave passage, 5.2 m depth, structure A, about 60 cm high
Structure A
Borehole
Relocated pole position
No voids were encountered during final foundation drilling for structuresI relocated the proposed pole location to 30 ft (10 m)
Structure A constructed 10 m to the east, and borehole preserved as aresearch well!Structure AOriginal location
Groundwater Exploration at Natural Bridge Cavern, San Antonio, Texas
TheNatural Bridge Cavernsare the largest known commercialcavernsin the U.S. state ofTexas.
The deepest part of the public tour is 180 feet below the surface, although undeveloped areas of the cavern reach depths of 230 feet.
Bat Cave Fault
Bat Cave FaultGlen RoseEdwards Aquifer
Study areaBat Cave Fault:
Normal Fault
~200 ft (60 m)UDPurpose of Geophysical Surveys:
Locate groundwater
L1L2L3L4 L5Phase-3 well
Resistivity profilesResistivity and NP profilesBat Cave Fault5 dry boreholes;$6,000 each
.
Bat Cave FaultA single tree
Resistivity Data along Profile L1 across Bat Cave Fault. Glen Rose FmEdwards Aquifer
152
Phase-3 Water WellE-W Line 2NWSEmilvoltFeetmilivoltHigh NP anomalyNP gradient is increasing towards southFeetABCGlen RoseEdwards Aquifer NP anomalies
New water well location
153
Phase-3 water wellSouthwestNortheast
Line 2Line 4L1 Edwards Aquifer Glen Rose FormationEdwards AquiferGlen Rose FormationEdwards Aquifer Glen Rose Formation
Bat Cave FaultSN
Reverse faults
Natural Bridge Cave Wild Tour: A trip along resistivity and NP surveys Line 1
Climbing down ~200 feet (60 m).
Reverse Faults
L1L2L3L4 L5Phase-3 well
VentLegendResistivity profilesResistivity and NP profilesBat Cave Fault
Locations of geophysical anomalies
New well location
Reverse fault
Drilling for Groundwater to a depth of 500 ft (150 m)
UPDownBat Cave FaultNewly drilled water wellWater well:
500 feet (~160 m)
Water encountered between 190-250 feet (60-75 m)
Water production: 140 litre/dakika
Geophysical Signatures of Active Faults of Houston, Texas
Mustafa SaribudakEnvironmental Geophysics Associates www.egatx.com
163
Houston
164
These faults are active but they are aseismic
167
There was a building here!
LPF-1LPF-2
There are more than 400 known active faults in the Houston area. This number was 150 in 1970.
PearlandHockley
Willow Creek
Tomball
Khan, S. 2008
Sherwood M. Gagliano, Ph.D. Coastal Environments, Inc-Louisiana (2013)
20 to 30 thousands of feet unconsolidated sediments in the Houston area
From Gagliano, S., 2013
A schematic cross-section of a growth fault These faults become listric with depth
Can geophysical methods locate faults?
The current practices of finding faults in the Houston area are: 1) surface investigation (phase 1); 2) drilling borehole and conducting gamma ray logging
Kuyu loglari
My first encounter with Houstons Active Faults-AEG Field Trip-2000 One question to the fieldtrip Leader : Have you tried geophysics in locating faults?
Perhaps a GPR method!U D
Site map for Long Point Fault
I-10Hwy. 6
L1L2
0 5 10 15 20 25 30 Ft EW
Fault ScarpGPR Data over the Long Point Fault-1
GPR data across Long Point Fault-2WEFault ScarpMore research is needed!
Perhaps a resistivity survey?
Houstons Major Active Faults: There are more than 400 known active faults in the Houston area. This number was 150 in 1970.
A Blind Test of a Resistivity Survey across Pearland Fault in the year 2007 This location is now a well developed residential neighborhoodProf. Dr. Carl NormanGeologist
Location of two resistivity profiles across the Pearland FaultRL2
Borehole locationRL1
FAULT ZONE
SandClayClay SandClayClayResistivity imaging data across Pearland Fault Line R1Line R2B-3 B-4
Key MarkersWe passed the test; but..!! We located the faults but they kept ignoring the geophysical methods
Benim ev
A photo showing the Hockley Fault Road Deformation-2004
L6L5L4L1L2L3
100200300400500600
FAULT SCARP?Patched Asphalt
NL7 FAULT SCARP UD(GPR and Gravity profiles are also taken along Line 1)
Shopping Mall being builtGravity survey on Highway 290-East Bound in 2005UpDownL1
Hockley Fault
Low Pass FilteredRaw Gravity DataSEmGalsmGalsRaw Bouguer Gravity ProfileFull Scale 0.4 mGalsNW
Gravity high on downthrown side!!
L1 Profile
L2 Profile Resistivity profiles at Hockley Fault
Fault scarp on the road surface; but no resistivity anomaly Silty-SandSandMain Fault
Fault Scarp? Amplitude LowHigh L1 Profile
L1 Profile
Atasozu: Her gordugun sakalliyi deden sanma!
192
NWSEL4 Profile
L5 Profile
L6 Profile SandSandSandSilt/Silty Sand
Resistivity Profiles Across the Main Hockley Fault
Fault Scarp SEResistivity and conductivity (EM31) profiles (L7) across the Hockley Fault
Ft
More GPR Data Along Line 1 How do these minor faults form in a shallow sedimentary environment?
195
Westbound 290
Eastbound 290
100200300400500600
MINOR FAULTS
N
U D UD U D U D UDFeetFS
300 feet wide fault zone
Highway 290Hockley Fault ZoneShopping MallLocation of Hockley Fault Zone Based on Geophysics Results Highway 290 is rebuilt by 2008 and new shopping mall is opened.
August 2010
April 2010
Hockley Fault Deformations Progress!
Main Hockley Fault and its minor fault along east feeder Main FaultMinor FaultMALLAugust 2010
FaultsDStone wall is separated from the brick wall
UpDownNew Mall Section on top of the Hockley Fault!
21 May, 2011
Dukkan sahibi ile bir konusma:MS: Do you see anything unusual with the construction of the store?
S.A: Yes, the floor keeps buckling..and there is a big crack just outside of the building deforming the corner of the building.
L1L2There are more than 400 known active faults in the Houston area. This number was 150 in 1970.
Houstons major fault system
Long Point Fault-L1
Long Point Fault-L2 A block of building was demolished here
Resistivity Data across the Long Point Fault at Moorehead & Westview Road Resistivity Data across the Long Point Fault at I-10 & Beltway 8
Willow CreekHoustons major fault system (The map from Khan, S. 2008)
TV and Newspaper:Year2009: Beckendorf Intermediate to be demolished, plaque to be erected in honor of schools namesake Tomball FaultA teachers experience in the classroom!
RES. Line
Tomball FaultDemolished Beckendorf Middle SchoolResistivity profile-The school building was still there when we did the geophysical surveys
R1R1
School West EntranceNS
125 FtMajor cracks and subsidenceCalicheSand Resistivity data across the Tomball Fault-note that the deformation is on both the up and downthrown sides
SandNS ~50 feet
Willow CreekHoustons major fault system (The map from Khan, S. 2008)
Willow Creek Fault looking east DU NNote that this fault dips to the north not to the southThis work was published in the Leading Edge of SEG, 2006
A schematic map of the Willow Creek Fault siteProfile L2 is the only line along which resistivity, magnetic, conductivity, GPR and gravity surveys were performed
Fault Scarp
Positive microgravity anomaly over the downthrown side; why?Micro-gravity data
I can comfortably say that almost all geophysical methods detect Houstons active faults-University of Houston
Kasirga: 2008 Yazi Hurricane Ike- Summer 2008My house
Location of Mt. Bonnell Fault and its associated karstic features, Austin, Texas
Mustafa Saribudak-Environmental Geophysics [email protected](Picture courtesy of Dr. Leon E. Long of University of Texas)
Glen Rose
MBF
Edwards Aquifer
Mt. Bonnell Fault!MBF
Potential Fault Scarp Locations
HWY 360West Park Dr.Bee Cave Dr.
Glen RoseEdwards AquiferRecharge ZoneFrom Hauwert 2010
Beckmann Quarry, SA, TXKirschberg Me.Kainer Fm.(Ferrill,D. et. al., 2007)
Where is Mt. Bonnell Fault?Height DriveHwy. 360 UpDown
Where is Mt. Bonnell Fault?DownUpWest Park Drive
Where is Mt. Bonnell Fault?Bee Cave Rd at Camp Craft RdUpDown
@#*&s@%sWhy dont you do some geophysics to locate the fault?! Glen RoseHighway 360Disappointed
Integrated Geophysical Methods Used in StudyMagneticsConductivityResistivityNatural Potential (NP)Ground Penetrating Radar (GPR)
Geophysical survey locations
232
The Natural-Potential Method (NP) utilizes the earths natural-electric field at the ground surface to detect and map groundwater pathways and geologic features. Typical applications include:
Detecting caverns and tunnels Locating leaks in dams, ponds and reservoirsNo Depth Estimation!
(Reynolds, 2000)NPCONTINUED
NP ContinuedLong-Line MethodGradient method
Resistivity Fieldwork
)
Resistivity measures resistivity contrast Weathered Limestone: 50-250 Ohm-mFresh Limestone: 250>Ohm-mClay: 1-10 Ohm-m Depth Exploration: of profile length
236
Ground Penetrating Radar (GPR)
GPR maps dielectric contrast: It is the ability to hold electrical currentClay: 12-35Limestone: 5-10Water: 81Air: 1Depth Exploration: Depends on the conductivity of the soil
237
Definition of Anomaly in Dictionary A deviation from the background, type, arrangement, or form.
238
UPDOWNHeight Drive
3D GPR Survey Area
Resistivity, NP, Magnetics & Conductivity Line
Mount Bonnell Fault (Geology)NWSEHEIGHT DRIVE AT HWY. 360
240
NWSE2D GPR profiles from Height Drive
Amp.
Glen RoseEdwards Aq.Bad quality GPR data
Strike of Mt. Bonnell Fault
Pipe
Pipe
Road
Pipe NGPR SLICES FROM 3D DATA
NWSE
Marble WallMagnetic DataConductivity DatamS/mnT
Mount Bonnell Fault)
Known Utility PipeGlen RoseEdwards Aq.
UPDOWNHeight Drive
Resistivity, NP, Magnetics & Conductivity Line
Mount Bonnell Fault NWSEHEIGHT DRIVE AT HWY. 360
250 271 292 313 334 355 376 397 418 439 Ft Ohm-mNWSE250 300 350 400 450 Ft mV
Marble Wall
Glen RoseTypical NP fault anomaly Edwards Aq.
No resistivity anomaly over the fault!
Extensive deformation in marble wall in the vicinity of the resistivity anomaly!
Most Successful Geophysical Methods Locating Mt. Bonnell Fault at Height Drive are Natural Potential and GPR Methods
MBF
246
Camp Craft RoadBee Cave Road
UPDOWN247
GPR LineResistivity, NP, Magnetic and Conductivity Line
Mount Bonnell Fault (Geology)
Incipient Sinkhole
DU
Observed Incipient Sinkhole
NW SE nTFeetFeet mS/mConductivity Data
Observed Incipient Sinkhole
Magnetic Data
MBF location by GeologyGlen RoseEdwards Aq.
Ohm/mmVNWSE
160 181 202 223 244 265 286 307 328 349
Incipient Sinkhole
MBF Sinkhole?Edwards Aq.Glen Rose
235 240 245 250 255 260 FtNWSE Feet
SINKHOLE
285 290 295 300 305 310 315 Feet NWSE
C O L L A P S E D A R E A Feet
Most Successful Geophysical Methods Locating Mt. Bonnell Fault at Bee Cave Road
Total Magnetic
Ground Conductivity
Natural Potential
Resistivity and GPR
Location of Mt. Bonnell Fault
Cave
Sinkhole
Collapsed zone
Fracture zonesIntegrated Geophysical Results:Recharge ZoneBased on this study and others that we are involved, karstic areas appear to be Heaven for geophysical methods
What do all these three fault locations have in common?West Park DriveHeight Drive at Hwy. 360Bee Cave Road
Colorado River, Austin, Texas
Mustafa Saribudak www.egatx.comWilliamson CreekSt. Elmo Railroad CutPilot Knob VolcanoThe Near-Surface Geophysical Mapping of an Upper Cretaceous Submarine Volcanism and its Associated Volcaniclastic Rocks, Austin, TX
Volcanoes in Austin?!2012 Austin Geological Society Field Guidebook cover The primary goal of this study was to obtain geophysical signatures of the volcanic rocks and associated Austin Chalk Group. It is borne out of personal interest..
AB
Stratigraphic column of Austin Chalk (Modified from Young and Woodruff, 1985)
Volcanic activity
Figure 3. West-east cross-section of Chapman oil field showing relation of serpentine mass to overlying and underlying formations.1 through 5 are sedimentary rocks; 6: hydrated volcanic lava, tuff 6: Hydrated volcanic rocks-Trap for oil and gas
A: Williamson Creek
B: St. Elmo Railroad Cut Locations of Volcanic Sites on a detailed Google Map Emerald Forest Dr.
M1M2M3M4R5R4R3R2R1MR
N 0 15 m ResistivityEmerald Forest DriveMeadow Creek DriveKvKv KvKvR6 R7 R8
KpcKpcKpc
Volcanic rocks (tuff and lava)ResistivityMagneticResistivityMagnetic and resistivityKv Vinson ChalkKpc Pyroclastic rocks Legend
Williamson Creek
Vinson limestoneVolcanic tuff, conglomerateLavaFault? NA view to the northwest of Williamson Creek
NVinson limestoneVolcanics A view to the northeast of Williamson CreekRevisiting the site many times allowed us to see structures that were not observable previously Newly found fault or fracture?
A pillow lava on the bed of Williamson Creek
A lapilli buried in the Vinson limestone?
A lava tube on the bed of the creek
Important:Prior to geophysical surveys, The volcanic section was interpreted to be a fault-bound graben, NOT an eruption center!
Important:Prior to geophysical surveys, The volcanic section was interpreted to be a fault-bound graben, NOT an eruption center!
D U D UVolcanic conglomerateLava
LimestoneLimestone
Collection of ferrous materials at the Williamson Creek prior to the magnetic surveys
Geometrics G-858 Cesium magnetometer surveys
NWSEProfile M1Profile M2Profile M3Profile M4nT
Exposed volcanic rocksExposed volcanic rocksVolcanic rocks are covered with alluvium and gravelVolcanic rocks are covered with alluvium and gravel0 20 40 60 80 100 120 140 160 m Magnetic profiles
Field pictures of resistivity surveysOn the northern bank-L1The purpose of the resistivity surveys was to map the vertical and horizontal distribution of the volcanic rocks in contrast to the Austin Chalk;The length of the resistivity profile determines how deep we can explore into the subsurface
On the southern bank-L6
Volcanic outcropsVinson ChalkVolcanic outcrops on the bed of Williamson CreekVolcanic outcropsVinson ChalkVinson ChalkLimestone block?Vinson Chalk NWSE Profile R1 Profile R2 Profile R3
Profile R4 Profile R5 NWSEVolcanic rocksVinson ChalkVinson ChalkVolcanic rocksVinson ChalkVinson Chalk
AB
N
C
NE SW
Williamson Creek bedVolcanic outcrop Outcrop of terrace depositsAAA
Profile R6Profile R7Profile R8Volcanic rocksVinson Chalk
Pseudo 3D resistivity map (A) and depth-slice (B) views across the Williamson Creek A limestone block appears to be enveloped by the volcanic rocks, which have been often observed and mentioned in the oil and gas literature relating to the serpentine plugs.
L4LAST resistivity-magnetic profileProfile L4, lengthwise, is the longest and, thus provides resistivity data as deep as 157 feet. I was trying to obtain some geophysical information that would evince the presence of an volcanic center; but I had no idea how that information manifest itself in the resistivity and magnetic data..
Resistivity (A) and Magnetic (B) Data along Profile MR-South BankBu ne?!!VinsonVinson
Kenneth A. Simmons, 1967-STGS Bulletin; p. 130. A depiction of Elroy-E Field, Travis County
Modelling of Magnetic Profile MR
TuffLavaBrecciated zone
AGS Field Guidebook, Caran et al., 2012
A north view from the St. Elmo Bridge-1940? L2Fault?
A north view from the St. Elmo Bridge-2014 Volcaniclastic rocksDessau ChalkL2
N
A south view from the St. Elmo Bridge Dessau ChalkVolcaniclastic rocksL1N
Resistivity data along profiles L1 (western) and L2 (eastern)Resistivity data does not indicate any fault offset!40 ft
Old and recent pictures of Pilot Knob volcano, Travis County, Texas
Geological cross-section-Year 2006WestEast
Location of geophysical profiles
Locations of Geophysical Profiles (1 and 2) on the Pilot Knob Geological Map
Resistivity and magnetic profile along Line 1
Resistivity (A) and magnetic (B) data along Profile 1
Resistivity and magnetic profile along Line 2 across the Pilot Knob volcano
Resistivity (A) and magnetic (B) data along Profile 2
Conclusions:
A volcanic eruption center was delineated at both Williamson Creek and Pilot Knob sites;
Current geological data was updated with the new findings of geophysical data;
A volcanic core of the Pilot Knob was mapped with the help of resistivity and magnetic data;
The magnetic method has long helped detect buried volcanic rocks. Since resistivity surveys can be deployed to map subsurface as deep as 1,000 to 1,400 feet, additional resistivity surveys could offer useful information on the structure volcanic and adjacent sedimentary rocks.
I would like to make a point by saying that this project has been a very challenging one: Getting to the essence of the project required a detective-like (Columbo) attitude to piece the facts together. Thank you for your attention! Detective Columbo
Oneriler!Iyi bir Jeofizikci nasil olunur?Yerbilimleri sevgisi ve bu sevgiyi merakla beslemek;En az 10 yil gerekir;Saglam bir jeoloji bilgisi;Her projede en az iki yontemin uygulanmasi;Ustun gayret ve ilgi-ozellikle arazi calismalarindaCok veri topla: sadece dipole-dipole yerine dipole-dipole + Schlumberger dizilimi kullan; veya 3 veya 5 sismik atisi yapmak yerine 7 veya 11 atis yap;En iyi jeofizik programlarini kullan; modelleme yap;Zaman uzmanlik cagi; Jeofizigin bir konusunda uzman olun! Cevrenizdeki jeolojinin farkinda olun.
Antalya-Konyaalti JeolojisiJeofizik profili
KaynakJeofizik profileKonya-altinda kirectaslarindan cikan bir kaynak
Fakat calisirken eglenmeyi unutma!
1 23
Carbonates and Evaporites ISSN 0891-2556 Carbonates EvaporitesDOI 10.1007/s13146-013-0155-4
Geophysical signatures of Barton Springs(Parthenia, Zenobia and Eliza) of theEdwards Aquifer, Austin, Texas
Mustafa Saribudak, Nico M.Hauwert &Alf Hawkins
1 23
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ORIGINAL ARTICLE
Geophysical signatures of Barton Springs (Parthenia, Zenobiaand Eliza) of the Edwards Aquifer, Austin, Texas
Mustafa Saribudak Nico M. Hauwert
Alf Hawkins
Accepted: 3 February 2013
Springer-Verlag Berlin Heidelberg 2013
Abstract Barton Springs is a major discharge site for
the Barton Springs Segment of the Edwards Aquifer and
is located in Zilker Park in Austin, Texas. Barton Springs
actually consists of four springs: (1) The Main Barton
Springs discharges into the Barton Springs pool from the
Barton Springs Fault and several outlets along a fault and
from a cave, several fissures, and gravel-filled solution
cavities on the floor of the pool west of the fault. The
thin-bedded unit on the southwest side of the fault is the
regional dense member, and the lower Georgetown For-
mation of the Edwards Group is exposed on the northeast
side of the fault. The offset of the fault is between 40 and
70 ft (1221 m). (2) Old Mill Springs is located in the
sunken gardens southeast of the Barton Springs Pool and
is primarily fed by relatively mineralized groundwater
from the Saline-Line Flow Route. (3) Eliza Springs is also
located along the Barton Springs Fault north of Barton
Springs pool. (4) The Upper Barton Springs is located
upstream of the Barton Springs pool on the south bank.
Surface geophysical surveys [resistivity imaging and
natural potential (NP)] were performed over the first three
springs (Main Barton, Old Mill and Eliza Springs).
Conductivity (EM) surveys were conducted in some areas
to distinguish utility lines. The purpose of the surveys was
to: (1) locate the precise location of submerged conduits
carrying flow to Main Barton Springs on the north and
south banks of the Barton Springs pool; (2) characterize
the hydraulic relation between the Main Barton, Old Mill
and Eliza Springs; (3) determine the potential location of
caves and active flow paths beneath the three springs; and
(4) characterize the geophysical signatures of the fault
crossing the Barton Springs pool. The geophysical sur-
veys revealed three general types of anomalies. Resistiv-
ity results from the south of the Barton Springs swimming
pool indicate presence of a thick, laterally extensive high
conductivity layer above the pool elevation. This high
conductivity layer is interpreted to be lateral clay depos-
its, either associated with the Del Rio clay or clay-rich
alluvial deposits associated with Barton Creek. These clay
layers appear to overlie the Edwards Aquifer south of the
pool. Also south and east of the pool are cylindrical high
conductivity anomalies that extend deeper than the
elevation of the submerged cave observed in Barton
Springs pool. These cylindrical high conductivity anom-
alies are also associated with NP anomalies, suggesting
groundwater flow. One hypothesis is that the alignment of
the high conductivity and NP anomalies corresponds to
the Saline-Line Flow Route that is known to discharge
primarily at Old Mill Springs, and is hydraulically con-
nected to Main Barton Springs and Eliza Springs. This
hypothesis is favored because the Saline-Line Flow Route
carries relatively mineralized groundwater and is known
to connect to Old Mill Springs and at some times Main
Barton and Eliza Springs. There are likely several conduit
paths to the pool from the southern part of Zilker Park.
Flow paths to Barton Springs from the east may be
localized within the uppermost leached and collapsed
members of the Edwards Group, which is known for its
extensive horizontal cave development. A third type of
This article has been granted an exception from the standard
measurement scale of the International System of Units for scientific
publishing as utilized by this journal.
M. Saribudak (&) A. HawkinsEnvironmental Geophysics Associates, Austin, TX, USA
e-mail: [email protected]
N. M. Hauwert
City of Austin Watershed Protection Department,
Austin, TX, USA
123
Carbonates Evaporites
DOI 10.1007/s13146-013-0155-4
Author's personal copy
anomaly, generally found west and immediately adjacent
to the Barton Springs Fault, southwest of Barton Springs
pool are circular low conductive features associated with
NP anomalies. These circular anomalies are interpreted to
be groundwater flow conduits bearing less mineralized
groundwater associated with the Sunset Valley and pos-
sibly Manchaca Flow Routes that are expected to cross
that area. The surveys allow an opportunity to compare
geophysical responses to directly observed features. The
Barton Springs Fault appears to be associated with cir-
cular high- and low-resistivity anomalies. Eliza and Old
Mill Springs also indicate significant resistivity and NP
anomalies suggesting presence of submerged conduits and
faults in the vicinity. Although it is obvious such conduits
are present adjacent to major springs, the surveys allow
examination of how such water-filled conduits appear
using various geophysical methods. Known underground
infrastructure was also included in the surveys to see how
air and water-filled pipes responded. An air-filled train
tunnel corresponded to a high-resistivity anomaly. Local
utility lines crossing the site showed no significant resis-
tivity anomaly but metal pipes were detectable with EM
conductivity surveys.
Introduction
Barton Springs discharge from the karstic limestone of
Edwards Aquifer (Fig. 1). The structural framework of the
Edwards Aquifer is controlled by Balcones Fault Zone
(BFZ) an echelon array of normal faults that has extended
and dropped the aquifer and associated strata from north-
west to the southeast (Small et al. 1996; Ferril et al. 2005).
Barton Springs is a major discharge site for the Barton
Springs Segment of the Edwards Aquifer into Barton Creek
about 3,400 ft (1,000 m) upstream of its mouth at the
Colorado River (Hauwert 2009, and see Fig. 2). The geo-
logic framework is highly faulted near Barton Springs
(Fig. 2). Fissures, conduits, and caves are commonly
encountered throughout the Barton Springs. Barton Springs
actually consists of at least four spring clusters, three of
which were originally named after the daughters of the
original owner of the Park, William Barton. The water
feeding the springs is derived from mixtures of different
sources, identified by distinct differences in water quality
and injected tracer breakthroughs (Hauwert et al. 2004;
Hauwert 2009).
1. The Main Barton Springs, or Parthenia Spring,
discharges into the Barton Springs pool near the
diving board at an obvious fault line. The thin-bedded
unit on the southwest side of the fault is the regional
dense member of the Edwards Group and is juxta-
posed with the lower Georgetown Formation of the
Washita Group which is exposed on the northeast
side of the fault. The offset of the fault is estimated
to be between 40 and 70 ft (12 and 21 m). Main
Barton Springs is supplied by a mixture of flows from
the Sunset Valley Flow Route, the Manchaca Flow
Route, and the Saline-Line Flow Route (Hauwert
et al. 2004).
2. Zenobia Spring is located in the sunken pool southeast
of Main Barton Springs and is also called Old Mill
Springs. This spring is primarily supplied by the
Saline-Line Flow Route, which is enriched in highly
mineralized water (Hauwert et al. 2004; Hauwert
2009). Hydraulic connection between Old Mill Springs
Fig. 1 Balcones Fault Zoneportion of the Edwards Aquifer.
Barton Springs are located in
the Barton Springs Segment
(from Hauwert 2009)
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123
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and Main Barton Springs is evident when Barton
Springs pool draining results in the flow of Old Mill
Springs to cease (Hauwert 2009).
3. Eliza Springs is located behind the concession stand
and is also called Concession spring. Eliza Springs is
primarily supplied by the Manchaca Flow Route of
the Manchaca groundwater basin (Hauwert 2009)
4. The Upper Barton Springs is located upstream of the
Barton Springs pool on the south bank. This spring is
supplied solely from the Sunset Valley Flow Route
(Hauwert 2009)
Based on local surface observations, a geologic cross
section illustrates the site geology roughly along the south
side of Barton Springs pool, from Main Barton Springs
through Old Mill Springs (Fig. 3). This line was selected
because it includes outcrops where the site geology is
directly determined, although some geologic features, such
as bedrock depth, the elevation of the contact between the
Georgetown Formation and the underlying Edwards Group,
and the location of an estimated fault near Old Mill Springs
are not directly observed and are estimated based on
available data.
In this study, geophysical survey methods (resistivity
and natural potential) are integrated for the shallow sub-
surface characterization of Barton Springs (Main Barton,
Old Mill and Eliza), their associated karstic features, and
flow paths of the springs. These methods were chosen for
their ability to rapidly map variations of their respective
physical attributes (e.g., electrical resistivity and ambient
electrical current).
Methods
Resistivity imaging (AGI SuperSting R1/swift system)
Resistivity imaging is a survey technique, which builds up
a picture of the electrical properties of the subsurface by
passing an electrical current along electrodes and measur-
ing the associated voltages. Resistivity is the electrical
resistance of a material and is inversely related to its
electrical conductivity. This technique has been used
widely in determining karst features and subsurface struc-
tures, such as faults and fractures. Used in this study was
AGIs SuperSting R1 resistivity meter with a dipoledipole
electrode array that is relatively sensitive to horizontal
changes in the subsurface than other arrays and provides a
2-D electrical image of the near-surface geology. Electrode
spacing varied between 7 and 15 ft (2.14.6 m). High-
resistivity (or low conductivity) anomalies may reflect air-
filled voids, while low-resistivity anomalies may register
clay-filled or high conductivity water-filled cavities.
Natural potential (NP)
Natural electrical (NP) currents occur everywhere in the
subsurface. Karst investigations are concerned with the
unchanging or slowly varying direct currents (dc) that give
rise to a surface distribution of natural potentials due to the
flow of groundwater within permeable materials. Differ-
ences of potential are most commonly in the millivolts
range and can be detected using a pair of non-polarizing
Fig. 2 Surface geology of theBarton Springs area (modified
from Hauwert 2009). Note on
this map that the Edwards
Group members are exposed
west of the Barton Springs
Fault, while clays and
limestones of the overlying
Washita Group are exposed east
of the fault
Carbonates Evaporites
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electrodes and a sensitive measuring device (i.e. a volt-
meter). Recent flow of groundwater through a conduit is
necessary for it to be detected using NP. Positive and
negative NP values are attributed to changes in geometry of
caves as well as variations in flow conditions. The source
of NP anomalies can also be due to changes in topography
or changing soil and rock conditions. It should be noted
that NP measurements made on the surface are the product
of electrical current due to groundwater flow and the sub-
surface resistivity structure. For this reason, NP data are
displayed together with the resistivity data. The NP data
were also collected at a station spacing of 7 and 15 ft
(2.14.6 m).
Because NP is a passive method (i.e., no energy was
introduced during the testing), it was allowed within 100 ft
(30 m) of endangered Barton Springs salamander habitat
without the need to further demonstrate its safety or obtain
a permit from the U.S. Fish and Wildlife Service.
Conductivity meter (EM31)
Conductivity surveys were performed using a Geonics
model EM-31 instrument only in specific areas of Zilker
Park south of Barton Springs pool gate. The EM31-MK2
conductivity unit maps the conductivity of the subsurface,
and can detect metallic and non-metallic materials, geo-
logic variations, buried materials, groundwater contami-
nants, or any subsurface feature associated with variations
in ground conductivity. The EM-31 unit is a one-man unit
with an intercoil spacing of 12 ft (3.7 m), which has an
effective exploration depth of 18 ft (5 m), depending on
the conductivity of the soil. The EM-31 conductivity is
measured in units of milliSiemen/meter (mS/m). EM31
surveys were performed specifically to locate known and
unknown utility lines in order to distinguish these from
natural features.
Results
A total of 13 geophysical survey profiles were performed in
and around the Barton Springs area (Fig. 4). Results are
presented in Fig. 5 through Fig. 16. All geophysical pro-
files are presented from west (left) to east (right) or north
(left) to south (right).
Line 1 Barton Springs Fault
Geophysical profiles along line 1 were directed to cross the
Barton Springs Fault southwest of Barton Springs pool
(Fig. 4). Although the Barton Springs Fault is not well
exposed at this location, it is exposed in the pool only about
300 ft (90 m) northeast and extrapolated through local
mapping (Small et al. 1996, Hauwert 2009). The resistivity
data reflect the crossing of the Barton Springs Fault at
station 95, read as feet along the survey line, where resis-
tivity contrast is highest and signatures are vertically offset
(Fig. 5). The resistivity profile also shows potential caves
between stations 60 and 120 ft at depths between 10 and
35 ft (310 m), indicated by both high- and low-resistivity
anomalies corresponding with a high NP anomaly. The NP
anomaly peaks west of the fault (between stations 60 and
Fig. 3 Geologic cross section,based on field mapping, across
Barton Springs Pool and Old
Mill Springs
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120 ft) where localized groundwater flow is interpreted.
Within Barton Springs pool itself, flow can be observed
discharging along the Barton Springs Fault, although most
flow actually discharges from a horizontal cave developed
in a ledge near the bottom of the pool about 40 ft (12 m)
west of the fault. At times large flows can be observed
issuing about 80 ft (24 m) west of the fault along the
continuation of the same ledge. The observations of spring
discharge within Barton Springs pool, the NP, and resis-
tivity data consistently indicate the main groundwater flow
conduits are located west of the fault near the south side of
Barton Springs pool.
Note that the survey line crosses a known waste-water
line, that is observed as a 10-in. (0.2 m) metallic pipe
crossing the tributary to the North that does not reflect in
either resistivity or NP results (Fig. 5).
Lines 2 through 7 South Zilker Park
A reconnaissance conductivity survey was taken in this
part of the study area (Fig. 6). Conductivity results indicate
a metallic pipe located at about 135 ft (41 m, see Fig. 4 for
pipe location). The pipe was not mapped here on City
of Austin utility line coverage. An example of the
Fig. 4 Site map showinglocations of Barton Springs,
geophysical survey lines,
mapped faults mapped utility
lines and some observed
features
Fig. 5 Resistivity and NP dataalong line 1 crossing Barton
Springs Fault southwest of the
pool
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conductivity data showing the pipe is given in Fig. 5. The
conductivity data were further processed by removing the
pipe interference (Z_edit in Fig. 5). The residual data
indicate a significant conductivity contrasts along the pro-
file between stations 200 and 225 ft. This observation
suggests a vertical contact (fault) between a low resistivity/
high conductivity material (interpreted as clay) to the east
and a higher resistivity/low conductivity material to the
west (interpreted as limestone). One interpretation based on
the geophysical survey and consistent with available local
surface geology is that the estimated location of the fault
shown extending through Old Mill Springs is actually
about 500 ft (150 m) west from where it is interpreted in
Fig. 2. This fault separates surface exposures of the Del
Rio Clay to the east from the Georgetown Limestone to the
west. A second interpretation is that clay-rich alluvium
thickens to 1520 ft (57 m) east of station 200 ft along
the survey line 2. Geotechnical borings are necessary to
determine the source of the clay material.
Six profiles, lines 2 through 7, were surveyed in front of
the south gate of Barton Springs pool (Fig. 4). Three of the
profiles (L2, L3 and L4) were taken in the EastWest
direction, whereas three other profiles (L5, L6 and L7)
were surveyed in the NorthSouth direction.
Line 2 was surveyed roughly west to east sub-parallel to
the pool fenceline and crossing within 50 ft (15 m) of the
south entrance gate to Barton Springs pool at station 110 ft
(Fig. 7). A dirt road leading to the south gate of Barton
Springs pool is marked on the resistivity data. The resis-
tivity data show a significant very low-resistivity anomaly
(dark blue in color) between stations 75 and 175 ft along
the survey line, and extending to depths of about 80 ft
(24 m). This feature is a thick conductive circular feature
that has a sharp contact with a more resistive unit (green
and red in color) at station 180 ft along the survey line.
The NP data along the same line show a NP anomaly
between stations 50 and 165 ft (Fig. 7). This anomaly
correlates well with the location of the circular conductive
feature on the resistivity profile. The source of NP anomaly
could be a submerged cave.
Figure 8 shows resistivity lines (3 and 4) and the NP data
taken along the resistivity line 4. As in Fig. 7, both resistivity
profiles indicate very low resistivity features such as a cir-
cular conductive feature in the western section of the profiles.
These conductive anomalies make sharp contacts with the
moderate resistivity layers (green in color) of 50200 Ohm-
m between stations 135 and 180 ft. It is possible that some of
the low-resistivity anomalies near the dirt road in lines 2, 3,
Fig. 6 Conductivity data werecollected along lines 2, 3 and 4.
All lines showed a pipe anomaly
as shown in this figure (see text
for more discussion)
Fig. 7 Resistivity and NP dataalong line 2 that parallels the
south gate fence. Note the sharp,
shallow resistivity contrast at
135 ft. There is a significant NP
anomaly indicating a water-
filled cave or conduit where the
low resistive anomaly is located
Carbonates Evaporites
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and 4 may be affected from the metal pipe identified using
EM conductivity, although generally the spacing is expected
to be too big to be influenced by small-scale pipes.
The NP data, which were taken along line 4, show an NP
anomaly between stations 0 and 150 ft. This anomaly cor-
relates well with the location of a bedrock conductive unit
on the resistivity profile. The source of NP anomaly could
be a cave that is located beneath or around a clay-rich unit.
Figure 9 shows the NorthSouth resistivity data along
lines 5 and 6, and the NP data taken along line 6. Lines 5
and 6 are separated about 50 ft (15 m). The NP data were
collected on a dry day and later repeated on a wet day to
observe the effects of varying flow conditions. Both
resistivity data sets indicate shallow (\20 ft or 7 m deep)horizontally extensive conductive features that could rep-
resent clay-rich layers. This low resistivity/conductive
feature has a characteristic sharp geometry with the sur-
rounding rock units. In addition, line 6 shows two well-
defined circular conductive features at a greater depth
below about 30 ft. A moderate resistive rock material (i.e.,
100 Ohm-m) is observed between the two circular con-
ductive features. Also a sharp offset in resistivity features,
possibly fault, is observed at station 200 ft. The deeper
circular conductive features could represent caves bearing
relatively mineralized solution, or conductive mineral/clay
coating on the conduit wall (i.e. fracture skins).
The NP data, which were taken along line 6, show a pair
of NP anomalies between stations 0 and 100 ft, and stations
150 and 200 ft, respectively. The source of both NP
anomalies could be a water-bearing cave.
Figure 10 shows the same resistivity data from lines of 5
and 6 with the NP data that were collected the next day
after a big rain, which caused the Barton Springs pool to
close for several days due to the flooding of Barton Creek.
The pair of NP anomalies observed in Fig. 9 during a dry
day was integrated into one large NP anomaly between
stations 50 and 200 ft during wet conditions. This obser-
vation indicates that the groundwater in the cave or con-
duit, which was charged by the recent rain, elevated the
groundwater level and enlarged the NP anomaly.
Figure 11 shows the resistivity and NP data of line 7
(see Fig. 3 for location). Line 7 is located 50 ft (15 m) east
of line 6. The resistivity and NP data sets do not indicate
any significant anomaly. The NP data of line 7 could reflect
simply a hydraulic gradient of groundwater decreasing
toward the Barton Springs pool. Line 7 seems to reflect a
background section where no significant resistivity or NP
anomalies are present.
Lines 8 and 9 Old Mill Springs
Lines 8 and 9 were collected to the southwest and south of
Old Mill Springs, respectively (Fig. 4). Figure 12 indicates
the resistivity and NP data taken along line 8. The resis-
tivity data indicate a pair of low and high anomaly located
between stations 60 and 105 ft. There is a known waste-
water line crossing this profile. It is not clear if the waste-
water pipe is the source for this resistivity anomaly. The
NP data indicate an anomaly between stations 290 and
390 ft. The relatively mineralized Saline-Line Flow Route
Fig. 8 Resistivity and NP dataalong lines 3 and 4 that run
roughly west to east across a
field near the south gate. Note
the blue conductive andassociated NP anomalies below
the pool level and bedrock that
could represent water-bearing
solution features
Carbonates Evaporites
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is known to pass through this area toward Old Mill Springs
(Hauwert 2009).
Line 9 was surveyed to the west of Old Mill Springs,
and is shown in Fig. 13 (see Fig. 4 for location). The
resistivity data show a pair of low- and high-resistivity
anomalies located between stations 60 and 120 ft. The
contrast between the two is quite sharp, and the maximum
depth of this anomaly is observed down to 50 ft (15 m).
The groundwater discharges from Old Mill Springs at an
elevation about 20 ft (6 m) below the line 9 surface closest
to Old Mill Springs. The NP data also indicate a NP
anomaly between stations 50 and 110 ft, corresponding to
areas of resistivity anomaly.
Lines 10 and 11 Barton Springs pool
Only NP surveys were allowed to perform inside the fences
of the Barton Springs pool due to potential for impacts
Fig. 9 Resistivity and NP dataalong lines 5 and 6. The NP data
were collected on a dry day
Fig. 10 Resistivity and NPdata along lines 5 and 6. The NP
data were collected 1 day after a
heavy storm
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Fig. 11 Resistivity and NPdata along line 7 that crosses
north to south across a field
South of Barton Springs pool.
Both data sets do not indicate
any significant anomaly. Note
the hydraulic gradient on NP
data, which is toward the north
where the Barton Springs pool
is located
Fig. 12 Resistivity and NPdata along line 8. The resistivity
anomaly observed between 60
and 100 ft is not associated with
NP anomalies. Note the sloping
NP data are interpreted to reflect
decreasing hydraulic gradient
towards the Barton Springs pool
Fig. 13 Resistivity and NPdata along line 9 next to Old
Mill Spring. A pair of high- and
low-resistivity anomalies
corresponds to an NP anomaly
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from resistivity surveys on endangered species of aquatic
salamanders living in the pool. Thus two NP lines, 10 and
11, were surveyed along the southern and northern banks of
the pool (see Fig. 4 for location). Figure 14 shows both NP
data profiles. Locations of some cultural features along the
profiles are shown as reference points. Note that an 8 ft
(2.4 m) high, 10 ft (3 m) wide concrete bypass culvert
structure underlies the sidewalk adjacent to the northern
side of Barton Springs pool. This bypass structure carries
flow from upstream Barton Creek, discharge from Eliza
Springs, and some leakage from the pool and underlying
groundwater flow.
The north bank NP profile indicates more NP anomalies
than the southern one. It shows basically four anomalies,
which are marked on the profile as A, B, C, D and E.
Sources for these anomalies could be due to water-bearing
karstic features such as caves, voids, fractures and faults, as
well as anthropogenic discharge pipes. Line 11 on the north
bank generally lies 1020 ft (36 m) away from the
bypass, and is not affected by water that continually flows
though the bypass, except for the area near anomaly C,
which approaches within 3 ft (1 m) of the bypass.
The NP data on the south bank indicate a very signifi-
cant NP anomaly D between stations 240 and 420 ft. This
anomaly corresponds to where the Barton Springs Fault
crosses the pool (see Fig. 3). There is another NP anomaly
C located between stations 160 and 220 ft. Anomaly C
could potentially reflect flow through the bypass, although
water can be observed rising from the floor of the bypass in
several places near anomalies C and D, that likely indicates
groundwater flow passing beneath.
Lines 12 and 13 Eliza Springs
Recent boring information from the area north of Eliza
Springs has verified the location of the Barton Springs
Fault is consistent with the mapped location shown in
Fig. 2. Lines 12 and 13 were surveyed to the east and west
of Eliza Springs, respectively (see Fig. 4 for location). The
NP data for line 12 were collected along a curved line
around Eliza Springs (Fig. 15). The NP data indicate a
steep NP anomaly between stations 70 and 140 ft. This
anomaly is probably due to discharge into and out of Eliza
Springs pool, including a known 2-ft diameter concrete
pipe that discharges to the bypass structure adjacent to the
north side of Barton Springs pool.
Line 13 was surveyed 150 ft to the east of line 12 (see
Fig. 4 for location). Figure 16 shows the resistivity and NP
data taken along line 13. The resistivity data indicate a pair
of low- and high-resistivity anomalies between stations 100
and 150 ft with a sharp contact boundary between them.
The NP data for line 13 indicate a low-NP anomaly between
stations 100 and 150 ft. This anomaly corresponds to where
the pair of low- and high-resistivity anomalies is observed,
and probably caused by a submerged cave. The NP data also
show a fault-like anomaly and appears to be accentuated by
the hydraulic gradient toward the pool. A high-resistivity
anomaly and low-NP anomaly are observed at station 30 ft,
which appears to correlate to a train tunnel for a small-gage
recreational train that serves Zilker Park.
Discussion
Geophysical surveys of Barton Springs pool may provide
details on locations of discrete groundwater flow that
would otherwise require many potentially disruptive wells
to decipher. While the geophysical results are subject to
interpretation and require prior experience to identify, they
reveal properties of the Barton Springs pool area that can
be further investigated with focused follow-up studies. The
significant anomalies are mapped on Fig. 17.
Fig. 14 NP data along thesouth and north banks of Barton
Springs pool. The northern bank
has more NP anomalies than the
southern bank. The anomaly D
on both profiles corresponds to
the location of Barton Springs
Fault
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Fig. 15 NP data along line 12next to Eliza Springs. Note that
NP anomaly indicates where
flow conduits carry flow to or
from Eliza Springs. A known
artificial subsurface discharge
pipe is also reflected as an NP
anomaly
Fig. 16 Resistivity and NPdata along line 13. WP1 and
WB3 are borehole locations.
WP1 was later converted into a
monitoring well. Both borehole
data sets indicate paleo-channel
materials between the depths of
15 and 35 ft. Note how the train
tunnel is reflected in the
resistivity survey
Fig. 17 Summary ofgeophysical anomalies detected
around Barton Springs pool.
One interpretation of a
groundwater flow path to Main
Barton and Eliza Springs is
consistent with the survey
results is shown, although other
interpretations are possible,
including that some of the south
NP anomalies are associated
with shallow perched
groundwater flow through
alluvial deposits
Carbonates Evaporites
123
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Deeper circular low resistivity/high conductivity fea-
tures are localized in specific areas south of Barton Springs
pool and extend vertically to depths of about 30 ft (9 m) to
as deep as 80 ft (24 m). Since the circular conductive
features were encountered in EastWest lines of 2, 3, and
4; and NorthSouth lines of 5 and 6, they are most likely
cylindrical features. It corresponds with the depth of the
submerged cave in Barton Springs pool whose elevation of
423 ft (129 m) msl is about 43 ft (13 m) deep below Line
2. It is unlikely that either anthropogenic fill, gravel quar-
rying, or alluvial fill would occur below the constantly
flowing base level of adjacent Barton Creek and regional
base level of the nearby Colorado River (410 ft or 125 m
msl; Solis et al. 2009). The 410 ft msl elevation is also the
deepest depth where terrace alluvial materials were
encountered by borings along the north side of Barton
Creek from Barton Springs pool to the Colorado River
(Fugro 2003). As NP anomalies, these features appear to
correspond with flowing groundwater. Therefore, the cir-
cular conductive features must be submerged bedrock
features, likely water-filled caves or a clay-filled, flow
conduit to Barton Springs.
One hypothesis is that the prominent low-resistivity
anomalies southeast of the pool are flow conduits from the
Saline-Line Flow Route to Main Barton and Old Mill
Springs. Chemical analysis of flow discharging from Main
Barton Springs suggests that mixing with the Saline-Line
Flow Route has already occurred as it discharges from the
south side of the pool at the Barton Springs Fault (Hauwert
et al. 2004). Yet flow from the Manchaca Flow Route
appears to arrive at Eliza that does not contain Sunset
Valley Flow Route contributions. Therefore, the source of
Eliza Springs must include a slightly deeper flow path
passing beneath the pool that does not contain Sunset
Valley Flow Route mixing. So a second hypothesis could
be that the cylindrical resistivity anomalies and NP
anomalies near the south gate are sensing the Manchaca
Flow Route to Main Barton and Eliza Springs.
Without resistivity surveys (which were not permitted
in the pool area for this study as a precaution for the
endangered salamanders), it is unclear if NP anomalies on
the southeast side and adjacent to the pool are associated
with NP anomalies near the south gate. Also unclear
without resistivity surveys is the depth of any ground-
water-bearing conduits below the southeast side of the
pool. The southeast pool NP anomalies could reflect
a number of hydrogeological conditions including
(1) groundwater following shallow paleodrainage chan-
nels in the alluvium, as seeping water is constantly
observed crossing the side pool sidewalk here, (2) solu-
tion cavities and fissure planes filled by pool backwater,
or (3) unobserved bedrock discharge orifices located in
the deep eastern end of the pool. The southeast pool NP
anomalies could reflect flow paths that cross underneath
the pool and Georgetown Formation and discharge from
Eliza Springs. The NP data obtained from the banks of
Barton Springs Pool also indicate correlating conduit
anomalies along the Barton Springs Fault.
NP and resistivity surveys reveal anomalies next to Old
Mill Springs (Fig. 12 and 13). The resistivity data indicate
a significant geological contact, which could be a fault,
between a pair of low- and high-resistivity anomalies. The
depth of these anomalies is about 35 ft (11 m) deep and
lies lower than the water-level of Old Mill Springs which is
roughly 20 ft (6 m) below line 9. This further supports the
hypothesis that mineralized groundwater flow associated
with the Saline-Line Flow Route is associated with low
resistivity/high conductivity and an NP anomaly. NP
anomalies encountered on lines 8 and 9 are consistent with
the crossing of the Saline-Line Flow Route to Old Mill
Springs.
There is a fault estimated to the east of Old Mill Springs
based on outcrop mapping and geotechnical borings on the
opposite side of Barton Creek (Fig. 17). The NP data show
an anomaly, likely localized groundwater flow, where the
fault is extrapolated; however, the resistivity data do not
indicate offset structures or high resistivity contrast in this
location. A fault contact between limestone and clay, if
present, should be clearly discernable on a resistivity sur-
vey. It is possible that the actual fault location is further
west or that the fault is reflected here as an eastward dip-
ping monocline rather than an abrupt fault.
The resistivity data obtained across the Barton Springs
Fault in the southern portion of Zilker Park (line 1 see
Fig. 17 for location) show highest resistivity contrast
where the Barton Springs Fault is mapped. An NP anomaly
peaks just northwest of the extrapolated fault location,
suggesting most flow is localized in the grainstone and
underlying kirschberg members on the upthrown side of the
fault. The elevation of a submerged cave in Barton Springs
pool (423 ft or 129 m msl) is 40 ft (12 m) lower than line 1
at the extrapolated Barton Springs Fault crossing 463 ft or
141 m msl. A low-resistivity anomaly is shown slightly
higher than this depth at the same station as the NP
anomaly peak. This low-resistivity anomaly may be an
extension of the cave observed in Barton Springs pool west
of the Barton Springs Fault, which is about 375 ft (114 m)
to the northeast.
NP data to the east of Eliza Springs indicate significant
anomalies. In addition, the resistivity data indicate a pair of
high- and low-resistivity anomalies that identify the Barton
Springs Fault. The NP anomaly suggests groundwater flow,
beyond the known pipe that discharges Eliza Springs flow
into the bypass. One explanation could be groundwater
flowing to Eliza Springs from the north. Another expla-
nation that may be more likely is groundwater flow
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Author's personal copy
bypassing Eliza Springs along the Barton Springs Fault that
discharges in the Colorado River.
Resistivity results obtained from the southern part of the
Barton Springs pool indicate shallow low resistivity (high
conductivity) laminar features similar in property to clay-
rich units extending to depths of about 20 ft (6 m).
Resistivity results obtained to the northeast of Eliza
Springs also indicate a thick clay unit (*20 ft, 6 m, ormore). This unit appears to sit on the Edwards Aquifer on
the west side of the Barton Springs Fault. The shallow low
resistivity signatures east of Eliza Springs on line 13 are
similar to the ones that are observed in the southern side of
the Barton Springs pool east of the south gate. Boring logs
from geotechnical holes drilled here indicate that a dark
reddish brown alluvial clay is present along the eastern end
of line 13 to depths varying from 15 to 35 ft (Fugro 2003).
One of the most interesting findings is the geophysical
responses at shallow observable features. In line 13, an
air-filled train tunnel is associated with a high-resistivity
anomaly and a low-NP anomaly. It is expected that an
air-filled tunnel would be associated with a high-resistivity
anomaly. Line 12 crossed a subsurface pipe carrying
discharge from Eliza Springs and showed a distinct NP
anomaly in that portion of the survey line. Future studies
could focus geotechnical borings or monitor well drilling at
the anomaly locations to verify the surface geology and
existence of submerged caves. Furthermore, more detailed
water-quality sampling and dye-tracing recovery from
these local wells as well as various spring discharges in
Barton Springs pool, the bypass, and Barton Creek may
help distinguish the location of specific flow paths. Previ-
ous water-quality sampling (Hauwert et al. 2004) suggests
that the major groundwater flow routes and their mixtures
are generally distinguishable based on chloride and sulfate
concentrations alone.
Conclusion
In summary, resistivity and NP results from the southern
part of the study area indicate presence of a thick, wide-
spread clay unit that appears to lie on the top of the
Edwards Aquifer. Cylindrical low resistivity/high conduc-
tivity anomalies associated with NP anomalies below the
bedrock south of the pool and east near Old Mill Springs
are hypothesized to represent groundwater flow conduits
associated with the relatively mineralized Saline-Line Flow
Route. NP anomalies from the banks of Barton Springs
pool may suggest where these Saline-Line flow conduits
cross beneath the pool (Fig. 17). Circular high-resistivity/
low-conductivity features associated with NP anomalies
adjacent to and west of the Barton Springs Fault are
hypothesized to reflect groundwater conduits for the Sunset
Valley and possibly combined Manchaca Flow Routes that
are know from previous studies to approach Barton Springs
from this direction. Resistivity surveys near observed faults
invariably show paired high and low contrasting resistivity
signatures and may show offsets in layered structures.
While some uncertainty remains for the exact groundwater
flow paths near Barton Springs, the geophysical surveys do
provide specific sites were groundwater flow can poten-
tially be directly examined using borings or wells.
Acknowledgments This work was funded by the EnvironmentalGeophysics Associates. The authors thank David Johns, PG, of City
of Austin for his permission to conduct geophysical surveys in and
around the Barton Springs pool, and his help during the correlation of
geophysical data with the geological data. David Johns and Ed Pea-
cock, PE, of the City of Austin Watershed Protection Department and
Brent Waters, Senior Hydrogeologist of Golder Associates in Rich-
mond, Virginia provided review and comments on this paper. The
authors also thank many others of City of Austin employees,
including Aquatics Manager Tom Nelson, Barton Springs pool
manager Wayne Simmons, Parks and Recreation Education Program
manger, Margaret Russell, geologist Sylvia Pope, and biologists Nate
Bendik and Dr. Laurie Dries who facilitated work between the months
of April and September of 2010. Dr. George Veni, Executive Director
of the National Cave and Karst Research Institute in Carlsbad, New
Mexico assisted in coordinating access to the study site.
References
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Hauwert NM (2009) Groundwater flow and recharge within the
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Travis and northern Hays Counties, Texas. A PhD dissertation;
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Geophysical signatures of Barton Springs (Parthenia, Zenobia and Eliza) of the Edwards Aquifer, Austin, TexasAbstractIntroductionMethodsResistivity imaging (AGI SuperSting R1/swift system)Natural potential (NP)Conductivity meter (EM31)
ResultsLine 1 Barton Springs FaultLines 2 through 7 South Zilker ParkLines 8 and 9 Old Mill SpringsLines 10 and 11 Barton Springs poolLines 12 and 13 Eliza Springs
DiscussionConclusionAcknowledgmentsReferences
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