large scale earthquake parcel classification mapping for...

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Large scale earthquake parcel classification mapping for increasing public

safety and enhancing planning and development within Clark County, NV

By

Optim Seismic Data Solutions, Inc

200 S. Virginia Street, Suite 560

Reno, NV 89501

and

6255 McLeod DR Suite #6

Las Vegas, NV 89120

FOR

Board of Regents, Nevada System of Higher Education

University of Nevada, Reno

Reference: Prime Award No. PO 4800000057-017, Subaward No. UNR-08-03

September, 2010

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Summary

Optim Seismic Data Solutions via a subcontract from the Nevada System of Higher Education

(NSHE) measured shallow shear-velocity velocities throughout the approximately 500 square

miles of Clark County as part of contract from Clark County Department of Development

Services. In all, 9006 individual seismic arrays/lines were deployed and spatially located using

Geographical Positioning System (GPS) in a systematic manner in order to maximize the data

density coverage of the database within Clark County. Typically, these non-intrusive linear

arrays were about 604 feet in total length and consisted of 24 equally spaced channels using a

single 4.5Hz vertical geophone at each channel. Seismic microtremor measurements, mainly in

the form of ambient noise from traffic, were recorded for an average of 20 to 30 minutes at each

location/array. Noise recordings were then processed and analyzed using the refraction

microtremor (ReMi) method and a single shear wave velocity profile was determined for each

seismic array. These profiles were then used to calculate Vs100’ (or Vs30m) the average shear

wave velocities down to 100 feet per IBC 2006 equation 16-41. Once these were determined, the

information was concatenated with the GPS spatial data into a single Geographical Information

Systems (GIS) seismic database which was used to model Vs100’ across Clark County.

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Contents

1.0 Introduction ............................................................................................................................... 4

2.0 Methods Used ........................................................................................................................... 5

3.0 Seismic data acquisition procedure:........................................................................................ 11

3.1 Seismic array location selection .......................................................................................... 12

3.1.1 Permits ......................................................................................................................... 13

3.2 Seismic array (line) deployment ......................................................................................... 25

3.3 Data acquisition ................................................................................................................... 26

3.4 Array coordinates and documentation................................................................................. 26

3.5 Array re-deployment and data upload ................................................................................. 26

4.0 Seismic data processing .......................................................................................................... 26

4.1 Modeling constraints ........................................................................................................... 28

4.1.1 Shortened arrays........................................................................................................... 28

4.2 Site Class Examples ............................................................................................................ 29

4.3 Shape of the dispersion curves ............................................................................................ 40

4.4 Quality Assurance of the Results ........................................................................................ 46

4.4.1 Blind Tests ................................................................................................................... 48

4.5 Velocity Reversals............................................................................................................... 51

5.0 Results: Microzonation Map ................................................................................................... 58

6.0 Other Deliverables .................................................................................................................. 62

7.0 Conclusions and Recommendations ....................................................................................... 62

8.0 References ............................................................................................................................... 62

Appendix A (on DVD): Microzonation Map produced by krigging using the Vs100’ values as

per IBC Site Class equation 16-41 Section 1613.5.5. The steps used for krigging is also

enumerated.

Appendix B (on DVD): One-dimensional (1D) shear wave (Vs) velocity models, and IBC

Vs100’ (Vs30m) at test locations. An illustration of the associated dispersion curve is also

included.

Appendix C (on DVD): GIS referenced shapefile map showing the Vs100’, Vs20’ and values

representing the average velocities calculated using IBC equation 16-41 (Table 2) for the top

100’, 20’ and 10’ for all Clark County seismic array lines.

Appendix D: List of seismic arrays for which geometry information was collected.

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1.0 Introduction

The Nevada System of Higher Education (NSHE) was contracted by Clark County Department

of Development Services (CCDDS) to create a soil classification map based on site-specific

shear-wave velocities (“microzonation map”) of the County (Figure 1). NSHE subcontracted

Optim SDS to perform this work under their supervision. Optim SDS employed the SeisOpt®

REfraction MIcrotremor (“ReMi”™) method to create the microzonation map. ReMi (Louie,

2001) is a non-intrusive, passive technique that uses ambient noise as its source.

Figure 1: Area within Clark County to be mapped for earthquake parcel classification. The County defined and

prioritized specific areas to be mapped.

Measurement of shear-wave velocity (Vs) in the shallow subsurface is essential for the

estimation of seismic hazard, the development of seismic-hazard maps, and the calibration of

recorded ground motion data. The site class measurements are represented by the average shear

wave velocity value for the top 100 feet or 30 meters (Vs100’ or Vs30m) as per IBC 2006

Section 1613.5.5. It is an integral to seismic design of structures per the International Building

Code and International Residential Code, (IBC) and (IRC) respectively. Site class directly

determines the Seismic Design Category (SDC) used by structural engineers and if not otherwise

determined through an approved test method, engineers must revert to the default site class.

Often this means adhering to a more stringent site class than the actual ground conditions would

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dictate and indirectly drives up the cost of design. Therefore, knowing the actual Vs100’ (or

Vs30m) values across Clark County can provide essential data necessary for seismic hazard

mitigation and also provide a direct cost savings for new construction and in the retrofitting of

existing buildings.

Based on this GIS seismic database, the project was intended to provide Clark County a single

shear-wave velocity based map with contoured values corresponding to the site classifications of

the IBC and National Earthquake Hazards Reduction Program (NEHRP) definitions for site

class, (Table 1). Furthermore, in collaboration with the City of Henderson (CoH) Building

Department, both velocity databases from the CCDDS and the CoH were integrated into a single

Vs database and the interpolated velocity map was based on the entire joint database to provide

seamless interpolation across the CCDDS and CoH boundaries. This velocity map will provide

city planners, building officials, design professionals, and researchers alike the opportunity to

determine the actual site class value of a particular parcel before a single site specific

investigation is performed.

Optim SDS performed all necessary tasks for completion of the work, including field data

acquisition, data processing and reports, working with University personnel to make the products

of the work available in a format to be mutually agreed upon during the term of this contract. As

part of the project, data from a total of 9006 sites were acquired, processed and submitted to the

City. This represents 100% of the total number of seismic lines (~9000) scheduled to be

collected as part of this project.

2.0 Methods Used

Optim SDS measured shear velocity as a function of depth at each of the locations using the

refraction-microtremor (ReMi) surface array technique. Louie (2001) developed the refraction

microtremor technique (commercially available as SeisOpt®ReMi

TM, © Optim 2001-2010) as a

more rapid and cost-effective method of measuring Vs30m to meet the IBC code (BSSC, 1997),

and to derive site conditions. This method has been peer reviewed and blind tested against both

borehole and multi-channel analysis of surface waves (MASW) (Louie, 2001; Stephenson et al.,

2005; Thelen et al., 2006). Refraction microtremor is a volume-averaging surface-wave

measurement, averaging velocities where geology is laterally variable, thus providing a more

appropriate measure of site effects on earthquake wave propagation than single-point data

obtained from downhole logs.

The essence of the ReMi technique is that ambient noise contains a usable signal that is

predictable from the velocity structure that is presumably caused mainly by human activities

(e.g. trucks, trains, and airplanes, human activity either induced or natural). Microtremor noise

from these sources excites Rayleigh waves, which are recorded by a linear array of 24 vertical

refraction geophones (Figure 2). The data acquisition procedure consists of obtaining 10-15, 30-

second sampled at 2 milliseconds (Figure 3). The Rayleigh waves contained in the recorded

microtremors (ambient noise) are separated from other wave arrivals using a two dimensional

slowness–frequency (p–f) transform of the noise records. The fundamental-mode phase-velocity

Rayleigh wave dispersion curve is picked along the minimum velocity of the energy envelope

within the slowness–frequency spectral image (Figure 4B). The spectrum is normalized as the

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ratio of the power spectrum at a particular frequency and slowness (inverse velocity) over the

average value for all slowness values at that frequency. Modeling of the dispersion curve (Figure

4A) produces a depth–velocity model (Figure 4C) that can be vertically averaged to the single

Vs30m value used by the IBC code (Table 2). The preferred profile will always be the profile

interpretation that results in the minimum number of layers to accommodate the observed

Rayleigh-wave dispersion and produces a best estimate, reliable and repeatable velocity

structure.

The IBC Site Class is calculated using the equations provided in the International Building Code

book. The following sections are extracted from its pages. Note that even though Vs100’ values

(average velocities as determined from equation 16-41 below) may give you an average

velocity that is Site Class B, the criteria defined in the IBC code book must be used (Table

3).

Table1: Table 1613.5.5 from 2006 International Building Code. This and the criteria described below must be used

to determine Site Class from the Vs100 values obtained during the project.

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Table2: Extract from 2006 International Building Code that shows how the Vs100’ that is used to determine Site

Class is calculated.

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Table3: Extract from 2006 International Building Code explaining the criteria used to classify a site. Note that Site

Classes A and B have to be further verified by a geotechnical engineer as described above.

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Figure 2: Refraction geophones (red sensors in picture) are placed on sidewalks or along paths to record ambient

noise generated by traffic, people walking or any other energy generated by active or passive source.

Figure 3: Ambient noise is recorded and analyzed to determine one-dimensional (1-D) shear wave velocity profile

(Figure 4) beneath each seismic profile.

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Figure 4: Recorded ambient (microtremor) data are first transformed into the frequency-slowness domain (Louie,

2001) (A). The dispersion curve is then picked (B) and modeled to obtain a 1D shear-wave velocity profile (C).

Vs=3255

Site Class B

b237s05_28

C

B

A

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3.0 Seismic data acquisition procedure:

The following summarizes the data acquisition procedure for the project. Data acquired is

processed using the SeisOpt® ReMi™ (© Optim, Inc) software to obtain the Vs30m (average

velocities in the top 100 feet as defined by IBC) values and the shear-wave velocity profile down

to a depth of 100 feet.

Data was collected throughout Clark County using the microtremor method (Louie, 2001). Field

crews were deployed with all necessary equipment, including: seismographs, GPS receivers,

seismic cables, geophones, hammer and strike plate, and laptops in both urban and rural settings

in two to four person teams. Site locations typically were reached via street approved vehicles,

off highway vehicles (OHV), and hiking, then placed alongside roadways, trails, open fields, or

open desert. During mission planning, crews would determine the appropriate equipment type,

modes of egress and digress, and the best data collection times depending on terrain conditions,

land use regulations, traffic conditions, and property owner stipulations, all in an effort to

minimize any potential impact to the environment and infrastructure while maximizing safety

and reducing any disturbances to the public. In some instances, special authorization had to be

obtained and site specific training requirements had to be met before accessing these site

locations. Optim SDS worked in concert with Clark County, local and federal government

entities, and property owners to adhere to all arrangements and conditions set forth and to obtain

any required permits before data collection was conducted.

In theory, the accuracy and the resolution of any model is a direct function of the data density of

the database. In determining the appropriate data density to be used, Optim SDS utilized

Southern Nevada Technical Guidelines as a basis for data density of 1 velocity sample per 36

acres. To aid in the capturing of evenly dispersed data, based on 1/36 acres, Optim SDS,

CCDDS, and the CoH internally developed a gridded subsection scheme based on the existing

book and section projections of Nevada (Figure 5). These GIS generated subsection layers were

loaded up onto the handheld GPS devices that were deployed to the field and helped guide data

collection efforts. However, due to limitations imposed by natural terrain, inaccessible areas,

large structures, and infrastructure obstructions, the data density across the entire project area

varied, rendering the 1/36 acre data density more of a guideline than an absolute standard. In

addition, in several areas, due to proximity to key infrastructure, identified geology of interest,

and velocity anomalies discovered in the data set as the project progressed, data density was

increased to better define the interpolated modeled surface in those areas. For instance, seismic

array locations were intentionally placed with strategic orientation in mind, crossing known

faults and fissure zones when possible. In order to maximize the potential to actually cross any

subsurface fault or fissure related features, arrays were placed perpendicular to the assumed

projected strike when possible.

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3.1 Seismic array location selection

All seismic array locations are intended to maintain an average test coverage or data density of 1

array per 36 acres with no less than 1000 feet measured midpoint to midpoint between each

array location. Utilizing an internally established grid (Figure 5) as a point of reference and aerial

photographs with the occasional site reconnaissance, a general site location is selected before the

array deployment.

Figure 5: Schematic showing section map subdivided into 36 sub-sections and odd numbers shaded for better

reference.

The established grid is based directly off the corresponding Township & Range associated with

the project area. Thus, each township equals 1-book, each book equals 36-square miles, and each

square mile or section is further divided down to 36 sub-sections. Each sub-section is

approximately 880 feet by 880 feet or approximately 17.7 acres. Therefore, we attempt to

perform a seismic array in 18 of the 36 sub-sections per section or 1 seismic array per 36 acres.

However, due to projection limitations some subsections are distorted, but the data density is

uniform.

The location of the seismic array is further refined on the following conditions encountered at the

proposed location:

Safety concerns

o High traffic and/or speed limit hazards

o Construction zones

Site overall accessibility:

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o Private property concerns

o Shoulder area and vehicle accessibility

o Array length of 604 feet to location length (does the line fit)

o Up to 2 channels may be omitted from the array (under cetain circumstances)

o Driveways (residential and commercial)

o Some driveways can be “bridged” with a hard line and others must be crossed

using wireless techniques.

Ambient noise and line geometry

o Relative slope and curvature of the array

o Parallel noise sources are preferred

o Very high energy perpendicular sources are avoided.

Other concerns

o Artificial underground voids (overpasses, tunnels, drainage channels, etc..)

3.1.1 Permits

As part subcontract to conduct thousands of site condition measurements for Clark County,

Optim SDS has gained access to several secure locations. These are listed below:

1. Bali Hai Golf Club

Location: 5160 Las Vegas Blvd. South

Las Vegas, NV 89119

Site website: www.balihaigolfclub.com

Google website: http://maps.google.com/maps?hl=en&ie=UTF8&ll=36.079835,-115.177531&spn=0.0154,0.043774&t=h&z=15

Permit required: No

Notes:

Cold called course General Manager.

Was put in touch with corporate office managing three of the local courses.

Arranged evening access.

2. Durango Hills Golf Club

Location: 3501 N. Durago Drive

Las Vegas, NV 892129

Site website: www.durangohillsgolf.com


Permit required: No

Notes:

Cold called course Manager.

Arranged early morning access through maintenance manager.

3. Angel Park Golf Club

Location: 100 South Rampart Blvd

Las Vegas, NV 89145

Site website: www.angelpark.com


http://www.balihaigolfclub.com/

http://maps.google.com/maps?hl=en&ie=UTF8&ll=36.079835,-115.177531&spn=0.0154,0.043774&t=h&z=15


http://www.angelpark.com/


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Permit required: No

Notes:

Cold called Manager.

Arranged course access on off day through course maintenance manager.

4. Royal Links Golf Club

Location: 5995 E. Vegas Valley Dr.

Las Vegas, NV

Site website: www.royallinksgolfclub.com

Google website: http://maps.google.com/maps?hl=en&ie=UTF8&ll=36.133456,-115.049193&spn=0.007695,0.021887&t=h&z=16 Permit required: No

Notes:


Arranged access to maintenance road.

5. Wynn Country Club

Location: 3131 Las Vegas Blvd. S

Las Vegas, NV 89109

Site website: www.wynnlasvegas.com


Permit required: No

Notes:


Worked through several different company divisions before given permission by legal

department.

Arranged early morning access though course maintenance manager.

6. Wild Horse Golf Club

Location: 2100 Warm Springs Road

Henderson, NV 89014

Site website: www.golfwildhorse.com


Notes:


Arranged through course maintenance manager.

No special time for access required.

7. Black Mountain Golf Club

Location: 500 Greenway Road

Henderson, NV 89015

Site website: http://www.golfblackmountain.com/golf/proto/golfblackmountain/


Permit required: No





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8. Black Mountain Industrial Complex

a. Olin Chor Alkali Products

Location: 8000 Lake Mead Parkway

Henderson, NV 89009

Site website: www.olinchloralkali.com


Permit required: No

Notes:

Cold called plant manager.

Met with plant manager, assistant manager and safety officer.

Field crew was required to attend regularly scheduled weekly training and to meet PPE

requirements.

b. Timet

Location: 8000 Lake Mead Parkway

Henderson, NV 89009

Site website: www.timet.com

Permit required: No

Notes:


Met with plant manager and safety officer.

Field crew was required to attend safety training and meet PPE requirements.

c. Basic Remediation Company

Location: 873 West Warm Springs

Henderson, NV, 89011

Permit required: No

Notes:


Met with operations manager to coordinate data collection times and identify areas that

were non-accessible.

Data collection was limited in scope due to lack of access from environmental concerns.

9. Clark County Water Reclamation main facility

Location: 8556 East Flamingo Road

Las Vegas, NV, 89122

Site website: www.cleanwaterteam.com


Permit required: No

Notes:

Cold called, was referred to several people, before given permission.

10. Rivers Mountain Water Treatment Facility

Location: 1299 Burkholder Blvd

Henderson, NV, 89015



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Site website: www.snwa.com


Notes:

Cold called the facility, talked with security.

Talked with Head of Security.

Helped access another small area of land to the north.

Field crew was required to attend brief safety training.

11. Nevada Energy

Site website: www.nvenegry.com

a. Clark Substation Location: N. Stephanie St, Las Vegas, NV


Permit required: No

Notes:

Stopped by at guard station and got phone number for central office, talked with several

people before being given number of plant manager.

Field crew was required to attend safety briefing and meet PPE requirement.

b. Walter M. Higgins Generating Station

Location: East Primm Blvd, Primm, NV


Permit required: No

Notes:

Called contact at Nevada Energy and was given plant managers contact information.

Field crew was required to have an escort.

12. Mohave Generating Station

Location: Bruce Woodbury Dr, Laughlin, NV

Site website: http://www.sce.com/PowerandEnvironment/PowerGeneration/MohaveGenerationStation/


Notes:

Cold called, and talk with plant manager

Met with plant manager, safety officer and chief engineer.

Granted access with the stipulation that Southern California Edison receives a copy of the

data.

Field crew was required to attend 2 hours of safety training and to inform the chief

engineer of work plans for the day.

13. Clark County Detention Basins

Location: Detention basins throughout the county

Site website: http://www.ccrfcd.org/




http://www.sce.com/PowerandEnvironment/PowerGeneration/MohaveGenerationStation/


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Permit required: No

Notes:

Cold called Clark County Flood Control District, was able to talk with the person in

charge of maintaining the detention basins of which there are several throughout the

county

Field crew was allowed access to basin under the following stipulations: cannot drive

over 5 mph to avoid dust, cannot drive on the floor of the basins, and must keep gates

lock expect with entering and leaving

14. Henderson Executive Airport

Location: 3500 Executive Terminal Dr

Henderson, NV 89052

Site website: www.hnd.aero


Permit required: No

Notes:

Cold called the General Manager.

Contact information was relayed to Clark County Department of Aviation who contacted

OptimSDS.

A meeting was arranged to be attended by all interested parties (Airport Management,

OptimSDS management, and Werner from the county Building Department).

Field crew was required to have an escort while on site.

15. North Las Vegas Airport

Location: 2730 Airport Dr

North Las Vegas, NV 89032

Site website: http://www.vgt.aero/01-home.aspx


Notes:

Made contact through Henderson Executive Airport.


16. Perkins-Overland Field

Site website: http://www.mccarran.com/ga_overton.aspx


Permit required: No

Notes:

Permission for access was given through North Las Vegas Airport.

17. Jean Sport Aviation Center

Site website: http://www.mccarran.com/ga_jean.aspx


Permit required: No

Notes:





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Permission for access was given through Henderson Executive Airport.


18. Big Bend State Recreation Area

Site website: http://parks.nv.gov/bb.htm


Permit required: No

Notes:

Field crew was granted access permission from onsite personnel.

19. Lead Mead National Recreation Area - see Figure 6 and 7 for map of permit areas.

Site website: http://www.nps.gov/lake/index.htm

Permit required: Yes

Notes:

Field crews were granted access per the permit and scheduled data collection with park

officials

a. Laughlin




http://www.nps.gov/lake/index.htm


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Figure 6: Map showing permit areas in the Lake Mead national Park, north of Laughlin.

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a. Overton



Figure 7: Map showing permit areas in the Lake Mead national Park, south of Overton.


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20. Coyote Springs - see Figure 8 for map of permit areas.

Site website: http://www.coyotesprings.com/


a. Pardee Homes (Developer)

Site website: http://www.pardeehomes.com/


Notes:

Contacted the developer with help from the CCBD

Field crews were granted access per the Seismic Revocable License (8747_4.DOC) dated

April 27,2010.

Scheduling was on a daily basis with onsite officials.

b. Coyote Springs Investment (Land Owner)

Permit required: Yes,

Notes:

Field crews were granted access per Seismic Research Revocable License.:

SeismicLicense (v_4) 3-8-10

Scheduling was on a daily basis with onsite officials.


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Figure 8: Map showing permit areas in the Coyote Springs region.

21. Desert Tortoise Large Scale Translocation Site - see Figure 9 for map of permit areas.




Notes:

Field crews were granted access per the permit NV-052-UA-10-08 dated Sep 24, 2010.

Scheduling was on a daily basis with BLM officials.

Figure 9: Map showing permit areas in the tortoise habitat region near Jean, NV.



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22. Lake Las Vegas - see Figure 10 for map of permit areas.

Site website: http://www.lakelasvegas.com/

a. North Shore



Notes:

Access was granted per the Right of Entry Agreement No.: OSDS- (06.14.10) dated June

17, 2010.

Data collection was scheduled with onsite personnel.

b. South Shore


Permit required: No

Notes:

Various HOA's were individually contacted and access granted and data collection

scheduled through those specific HOA's. Assistance from the CoH was used.

Figure 10: Map showing permit areas in the Lake Las Vegas region.



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23. Hiking Areas in Book 192 North - see Figure 11 for map of permit areas.


Notes:

Permission for these areas was piggy backed onto the Tortoise Permit, NV-052-UA-10-

08 dated Sep 24, 2010.

Scheduling was on a daily basis with BLM officials.

Figure 11: Map showing permit areas in the tortoise sanctuary region in book 192.

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24. Wetlands Park – Clark County Parks and Recreation.

Location: 7050 Wetlands Park Lane, Las Vegas, NV

Site website: http://www.accessclarkcounty.com/depts/parks/locations/pages/wetlands.aspx


Permit required: No

Notes:

Cold called facility supervisor.

Scheduled data collection through onsite personnel.

Field crew was granted access permission but had to remain on dirt roads while driving

vehicles.

25. Crystal Ridge (aka Ascaya)

Site website: http://ascaya.com/#/welcome_intro/


Permit required: No

Notes:

Contacted developer with help from the CoH.

Scheduled data collection through developer and coordinated with onsite personnel.

3.2 Seismic array (line) deployment

Seismic cables are deployed at the array location in a linear fashion.

Various configurations are possible, for example: 1*24 channels, 2*12 channels, 4*6

channels, etc.

Geophone spacing is built in to the cables at 8 meters (26.24 feet). This spacing is

consistent throughout all the project array sites unless otherwise specified.

Geophones (24 total) are deployed and connected to the seismic cable with a maximum

lateral tolerance equal to the individual geophone cable length or approximately 38

inches.

The geophones are planted at no more than 15° from vertical.

Up to 2 geophones may be deleted from a survey.

The curvature of the array is restricted to no more that 5% to 10%, depending on site

conditions, of the total array length before geometry information needs to be aquired.

The total elevation change across the array is limited to 5% to 10%, depending on site

conditions, of the array length before geometry information needs to be aquired.

Seismic data acquisition hardware is connected to the cable. (24-bit digital seismograph,

internal GPS, etc.)

Horizontal geometry was measured at each of the 24 geophones. A high resolution GPS

unit was used surveyed for latitude and longitude

Vertical geometry was measured at each of the 24 geophones using a high resolution GPS

unit or a leveling rod.

Geometry was obtained for 467 of the seismic arrays. These are listed in Appendtix D.

Geometries were applied to the data during data processing.



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3.3 Data acquisition

Once on a site, seismic arrays were deployed using linear arrays consisting of 24

geophones with 8 meters (26.24 feet) geophone spacing for a total array line length of

184 meters (603.67 feet).

Ambient noise microtremors were then recorded using standard vertical 4.5 Hz

geophones recorded at a rate of two milliseconds for intervals of 30 seconds each. In all, a

total of 12 to 20, 30 second recordings were collected for each seismic array. All raw

seismic data was collected utilizing Seismic Sources Company’s 24 channel, DAQLink II

digital seismographs and the seismic data acquisition system software VibraScope V2.4.12

or higher. Figure 3 depicts the field crew during actual data collection. In addition, hammer

hits using an 8 pound or 10 pound sledge and strike plate were collected at approximately

15 feet and 30 feet off both ends during normal passive data collection to increase high

frequency energy. This was especially useful in low energy environments, typically rural

settings away from traffic and other ambient noise sources.

During the acquisition phase, data is monitored for energy content of the ambient noise

and energy anomolies caused by power utilities, wind and other interferences that would

adversely affect the data.

Data irregularities are investigated in the field and corrected if possible and documented

if not.

3.4 Array coordinates and documentation

While data aquisition is being performed, the array endpoints are surveyed for latitude,

longitude, and elevation using a high resolution GPS. These coordinates provide a two-

dimensional orientation of the array with respect to geophones 1 and 24.

The first GPS point is recorded at geophone 1 and the second GPS point is recorded at

geophone 24.

In addition, a single digital photograph is taken of the fully deployed array to document

site conditions.

3.5 Array re-deployment and data upload

Once data aquisition and array documentation is completed all the seismic line hardware

is disconnected and properly stored for travel to the next array location. The data

collection procedure begins for the next seismic line from Section 3.1 of this document.

At the close of each day all data is uploaded for data processing and analysis.

If the uploaded data does not contain adequate Rayleigh-wave energy then a request may

be made to repeat the survey.

4.0 Seismic data processing

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The noise records collected above were processed using the SeisOpt® ReMi™ software (© Optim,

Inc., 2001-2008) that uses the refraction microtremor method (Louie, 2001). The refraction

microtremor technique is based on two fundamental ideas. The first is that common seismic-

refraction recording equipment, set out in a way almost identical to shallow P-wave refraction

surveys, can effectively record surface waves at frequencies as low as 1 Hz. The second idea is that a

simple, two-dimensional slowness-frequency (p-f) transform of a microtremor record can separate

Rayleigh waves from other seismic arrivals, and allow recognition of true phase velocity against

apparent velocities. Two essential factors that allow exploration equipment to record surface-wave

velocity dispersion, with a minimum of field effort, are the use of a single geophone sensor at each

channel, rather than a geophone “group array”, and the use of a linear spread of 24 geophone sensor

channels. Single geophones are the most commonly available type, and are typically used for

refraction rather than reflection surveying. The advantages of ReMi from a seismic surveying point

of view are several, including the following: It requires only standard refraction equipment; it

requires no triggered source of wave energy; and it will work best in a seismically noisy urban

setting. Traffic and other vehicles, and possibly the wind responses of trees, buildings, and utility

standards provide the surface waves this method analyzes.

There were three main processing steps:

Step 1: Create a velocity spectrum (p-f image) from the noise data: The distinctive slope of

dispersive waves is a real advantage of the p-f analysis. Other arrivals that appear in microtremor

records, such as body waves and airwaves cannot have such a slope. The p-f spectral power image

will show where such waves have significant energy. Even if most of the energy in a seismic record

is a phase other than Rayleigh waves, the p-f analysis will separate that energy in the slowness-

frequency plot away from the dispersion curves this technique interprets. By recording many

channels, retaining complete vertical seismograms, and employing the p-f transform, this method

can successfully analyze Rayleigh-wave dispersion where SASW techniques cannot.

Step 2: Rayleigh-wave dispersion picking: Picking is done along a ``lowest-velocity envelope''

bounding the energy appearing in the p-f image. This ensures that the picks are representative of true

velocities rather than apparent velocities, since noise is assumed to come from all directions. Picking

a surface-wave dispersion curve along an envelope of the lowest phase velocities having high

spectral ratio at each frequency has a further desirable effect. Since higher-mode Rayleigh waves

have phase velocities above those of the fundamental mode, the refraction microtremor technique

preferentially yields the fundamental-mode velocities. Higher modes may appear as separate

dispersion trends on the p-f images, if they are nearly as energetic as the fundamental. Spatial

aliasing will contribute to artifacts in the slowness-frequency spectral-ratio images. The artifacts

slope on the p-f images in a direction opposite to normal-mode dispersion. The p-tau transform is

done in the space and time domain, however, so even the aliased frequencies preserve some

information. The seismic waves are not continuously harmonic but arrives in-groups. Further, the

refraction microtremor analysis has not just two seismograms, but 10 or more. Hence severe

slowness wraparound does not occur until well above the spatial Nyquist frequency which is about

twice the Nyquist in most cases.

Step 3: Shear wave velocity modeling: The refraction microtremor method interactively forward-

models the normal-mode dispersion data picked from the p-f images with a code adapted from Saito

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(1979, 1988) in 1992 by Yuehua Zeng. This code produces results identical to those of the forward-

modeling codes used by Iwata et al. (1998), and by Xia et al. (1999) within their inversion

procedure. The modeling iterates on phase velocity at each period (or frequency), reports when a

solution has not been found within the iteration parameters, and can model velocity reversals with

depth.

4.1 Modeling constraints

The preferred profile will always be the profile interpretation that results in the minimum number

of layers to accommodate the observed Rayleigh-wave dispersion and produces a best estimate,

reliable and repeatable velocity structure. Because forward modeling is used rather that an

inverse method to obtain our velocity-depth model, we are able to test the necessity and

sensitivity of the data to both layer thickness and layer velocity. The resultant model is therefore

the simplest to explain the data. This follows from Occam's razor principle that "entities must not

be multiplied beyond necessity", which simply states that “one should not increase, beyond what

is necessary, the number of entities required to explain anything”.

4.1.1 Shortened arrays

Due to artifacts resulting from topographic changes along the length of the array, some geophone

traces were required to be removed from analysis to allow more accurate determination of the

velocity structure. These arrays are:

2173606 geophones used: 1 to 15

2173618 geophones used: 13 to 24

Some remote areas were not accessible by vehicles or off highway vehicles (OHV). To access

these areas, equipment had to be hiked to each location. Due to the physical burden of the 604

foot seismic cable and site conditions, a shorter 230 foot long cable was utilized with 10 foot

spacing between each of the 24 geophones. There were 107 seismic arrays that were acquired

with 230 feet total length. These array lines are:

1233310 1261031 1261518 1402613 1920218 2172808

1233314 1261106 1261520 1402626 1920230 2172810

1260403 1261108 1261522 1601904 1920324 2172814

1260405 1261110 1261528 1601905 1920335 2172821

1260409 1261112 1261532 1601908 1920336 2172827

1260501 1261114 1261807 1601924 1923616 2172834

1260502 1261116 1261809 1601935 2040209 2173314

1260505 1261118 1261816 1602215 2171008 2230505

1260506 1261120 1261818 1603017 2171017 2230511

1260508 1261122 1261823 1613329 2171028 2230801

1260514 1261123 1261827 1640408 2171535 2230808

1260518 1261126 1262326 1640409 2171536 2230810

1260530 1261128 1262331 1640419 2172135 2230813

1260533 1261130 1400416 1640420 2172203 2231734

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1260713 1261132 1402413 1640422 2172205 2232014

1260806 1261134 1402424 1640430 2172222 2232034

1260925 1261508 1402425 1920205 2172232 2232910

1261019 1261516 1402601 1920216 2172719

Despite the shorter line lengths, the Raleigh-wave dispersion data still contained sufficient detail

to enable a 100 foot velocity profile to be obtained.

4.2 Site Class Examples

Vertically averaged shear-wave velocities resulted in single Vs30m values which corresponded

to sites class B, C, and D as defined by the IBC code (see Table 2). The following are examples

of data from each of these three site classes.

Site Class B examples are shown in Figures 12, 13, 14 and 15. Note that here Site Class B is

defined based just on the velocities. The criteria described in Table 3 is must be used on a

site by site case to make sure it can be classified as Site Class B.

Site Class C examples are shown in Figures 16, 17 and 18.

Site Class D examples are shown in Figures 19, 20, and 21.

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Figure 12: Example of Site Class B data as determined from velocities ONLY. Recorded microtremor data are

first transformed into the frequency-slowness domain (Louie, 2001) (A). The dispersion curve is then picked (B) and

modeled to obtain a 1D shear-wave velocity profile (C).

Vs=2732

Site Class B

b191s18 _21

A

B

C

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Vs=3288

Site Class B

b125s18_08

C

B

A

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Vs=2556

Site Class B

b216s30_07

C

B

A

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modeled to obtain a 1D shear-wave velocity profile (C). As the photograph on the upper right shows this is a

mountainous area.

Vs=4121

Site Class B

b126s27_35

C

B

A

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Figure 16: Example of Site Class C data. Recorded microtremor data are first transformed into the frequency-

slowness domain (Louie, 2001) (A). The dispersion curve is then picked (B) and modeled to obtain a 1D shear-wave

velocity profile (C).

Vs=2038

Site Class C

b216s06_12

C

A

B

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Vs=1635

Site Class C

b237s22_14

C

B

A

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Vs=1665

Site Class C

b216s06_24

C

B

A

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Figure 19: Example of Site Class D data. Recorded microtremor data are first transformed into the frequency-



Vs=1183

Site Class D

b031s34_36

C

B

A

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Vs=734

Site Class D

b071s19_04

C

B

A

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Vs=980

Site Class D

b223s22_21

C

B

A

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4.3 Shape of the dispersion curves

The shape of the dispersion curve varies due to the differing characteristics of the sub-surface

velocity structure. Figures 22 to 26 illustrate some of the typical variations observed.

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Figure 22: Example showing variation in the observed dispersion curve. Recorded microtremor data are first

transformed into the frequency-slowness domain (Louie, 2001) (A). The dispersion curve is then picked (B) and


C

B

A

Vs=3193

Site Class B

b204s10_36

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Vs=1211

Site Class C

b264s23_20

C

B

A

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Vs=1018

Site Class D

b161s04_26

C

B

A

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Vs=1389

Site Class C

b223s01_18

C

B

A

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Vs=3127

Site Class B

b164s22_35

C

B

A

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4.4 Quality Assurance of the Results

Quality assurance of results begins by plotting of the velocity models within each section – (ca.

18 parcel measurements), as shown in Figure 27. Focus is accuracy of the average velocity

model in the upper 100 feet.

First check is to make sure the models are consistent within the section. Information from spatial

location, topographic, and geologic maps are utilized. If one model differs from surrounding

measurements, or is anomalous given known topographic changes, remodeling of the dispersion

curve picks is the first step. An alternate model which is more consistent may be able to be

derived. For some data sets, re-analysis of the original data may then occur. This may involve

adjustment of picks along indistinct dispersion curves or reconsideration of the curve itself.

Consistency of models with adjacent sections is also verified.

If there are anomalously high velocity layers within the upper 100 feet, the reliability of low

frequency dispersion curve picks is examined. In some cases, the accuracy of the dispersion

curves at low frequencies is unclear. Again, picks may be adjusted and the dispersion curve at

low frequencies is reconsidered.

If the site is classified as a Site Class B, the high frequency data is more carefully scrutinized to

ensure there is velocity information to determine layers in the upper 20 feet.

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Figure 27: Plot showing velocity versus depth plots for all arrays in b223s12 to a depth of 100 feet. The vertical red

line indicates a velocity of 2500 ft/s, while the horizontal red lines indicate depths of 10 ft and 20 ft. The values

along the top each model are the Vs100’, Vs20’ and Vs10’ values representing the average velocities calculated

using IBC equation 16-41 (Table 2) for the top 100’, 20’ and 10’

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4.4.1 Blind Tests

“Blind” tests were periodically conducted to test the repeat ability of the data and analysis

results. Seismic data was collected using comparable acquisition equipment by Jim O’Donnell,

of Las Vegas, independently at the same location of seismic arrays obtained by OptimSDS. Test

locations were spatially dispersed in the map area where data collection was currently occurring.

Data acquisition for the two datasets occurred simultaneously. Excerpts of the same ambient

noise were therefore recorded by both datasets. Analysis results of the blind test data were

compared with that obtained by OptimSDS. An example is shown in Figure 28. The IBC Vs30m

values obtained by the two datasets, which are listed in Table 4, were then submitted each quota

to Clark County in fulfillment of contract requirements.

Figure 28: Example showing comparison of blind test data with the map data at b123s26_24: (A) the modeled

frequency-slowness domain; (B) the dispersion curve picks; and (C) the modeled 1D shear-wave velocity profiles

and Vs30m values.

A

B C

OptimSDS

Test

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Table4: List of Vs30m results from the map compared with those obtained through independent blind tests.

Quota 1 Vs Map (ft/s)

Vs Blind (ft/s)


Vs Blind (ft/s) Line

Line

1621803 1509 1524

1633620 3039 3128

1621921 1333 1353

1633621 3218 3296

1622202 1300 1364

1762118 3004 3101

1622633 1093 1096

1762132 3280 3273

1622932 1303 1417

1770114 950 940

1623121 1742 1783

1770119 1031 1016

1760335 3639 3410

1770808 1816 1917

1761325 2889 2898

1770830 2352 2201


Vs Blind (ft/s)



Line

1610217 1274 1202

1400417 1203 1212

1610325 1319 1408

1400622 987 944

1630221 2560 2593

1401417 1920 1732

1630411 3317 3149

1401621 1117 1029

1630612 3408 3016

1401711 996 1007

1630914 3167 3516

1402305 2536 2464

1631005 3124 3234

1402320 2538 2577

1631105 2880 2990

1403534 1759 1694


Vs Blind (ft/s)



Line

1250132 1047 1085

1611116 1493 1467

1250701 2997 3248

1611407 1094 1124

1252326 1102 1109

1613630 1454 1257

1252529 1396 1409

1640304 2476 2265

1252616 1282 1271

1640309 2123 2145

1253434 1123 1061

1640317 2394 2427

1253535 1282 1249

1751432 2732 3020

1253632 963 959

1751434 2823 2525

1751611 2671 2711


Vs Blind (ft/s)



Line

1380729 2736 2816

1260210 2910 2964

1380809 2691 2853

1260604 2997 2898

1381325 1550 1437

1260733 2723 2740

1381519 2855 2953

1260911 2831 2871

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1381928 3101 3164

1261136 3028 3324

1382424 1298 1320

1261810 2646 2604

1382822 3191 3067

1262503 2732 2901

1383112 2648 2822

1262613 2847 2808


Vs Blind (ft/s)



Line

2641306 1517 1680

0412622 1141 1208

2641508 1266 1270

0413424 715 732

2642431 1098 1067

0420225 2011 1953

2642834 1075 1051

0701330 1323 1295

0702411 1171 1200


Vs Blind (ft/s)

0713034 1415 1405

Line 2370801 1778 1761 2371608 1590 1608 2371619 1436 1543



0090419 1483 1419 0091417 956 939 0091517 1325 1322 0092225 1402 1392 2160607 2166 2237 2160722 3039 2870 2171004 2568 2583 2171229 2166 2205 2172603 2210 2332 2230102 1683 1658 2230205 1402 1358 2230325 1368 1361 1232624 1461 1445 1232331 1554 1479 1220927 1391 1522

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4.5 Velocity Reversals

Caliche is distributed across much of the Las Vegas region. The high velocity caliche deposition

within subsurface layers can result in high velocity layers within the velocity-depth profile, with

lower velocity material below. These are referred to as velocity “reversals”. If reversals are

present in several models within a section, the depth of the inversion layer is attempted to be

fixed so that is occurs at the same depth throughout the surrounding area. The assumption is

made that the geology is not varying greatly over the short distances considered, and that the

caliche is developing in the same sedimentary layer within the section. Seismic lines

immediately adjacent to those with inversions may be modeled with an inversion layer even if

they can be modeled without an inversion, based on this assumption. Examples of data with

inversions are given in Figures 29 to 32.

In some cases, to maintain constant bedrock velocities within a section with topographic highs,

small reversals may be introduced into the model (Figures 33 and 34).

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Figure 29: Example of Site Class D data that produced model with velocity reversal a depth. Recorded microtremor

data are first transformed into the frequency-slowness domain (Louie, 2001) (A). The dispersion curve is then

picked (B) and modeled to obtain a 1D shear-wave velocity profile (C).

Vs=1178

Site Class D

b138s01_13

C

B

A

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Figure 30: Example of Site Class B data that produced model with velocity reversal a depth. Recorded microtremor


picked (B) and modeled to obtain a 1D shear-wave velocity profile (C)

Vs=2527

Site Class B

b204s20_27

C

B

A

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Figure 31: Example of Site Class C data that produced model with velocity reversal a depth. Recorded microtremor



Vs=1262

Site Class C

b264s22_07

C

B

A

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Figure 32: Example of Site Class D data that produced model with velocity reversal a depth. Recorded microtremor



Vs=1182

Site Class D

b161s20_15a

C

B

A

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Figure 33: Small inversions are introduced into the model so as to maintain constant bedrock velocities within a

section with topographic highs. Example for a Site Class C site.

Vs=1205

Site Class C

b264s28_21

C

B

A

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Figure 34: Small inversions are introduced into the model so as to maintain constant bedrock velocities within a

section with topographic highs. Example for a Site Class D site.

Vs=1188

Site Class D

b264s33_10

C

B

A

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5.0 Results: Microzonation Map

As part of the project, data from a total of 9006 sites were acquired, processed and submitted to

the City. This represents 100% of the total number of seismic array lines (~9000) scheduled to be

collected as part of this project. Figure 35 depict these seismic array locations across Clark

County. More detailed maps in Figure 36 display the Las Vegas Valley (Figure 36(a)), the I15

southern corridor including Jean and Primm (Figure 36(b)), Coyote Springs (Figure 36(c),

Moapa Valley, Longdale, and Overton (Figure 36(d)), and Laughlin (Figure 36(e)).

Appendix A (on DVD) shows the microzonation map generated using ArcGIS and the Vs100’

values determined from the distribution of seismic arrays in Clark County. The method of

krigging was used to produce this map. The microzonation map has been produced in a format

(digitally delivered to Clark County) so it can be easily integrated into Clark County’s present

internet based public information system. The map for the City of Henderson was completed in

tandem with the Clark County microzonation project. As such, the map that is produced took

into account the microzonation values obtained in the adjoining City of Henderson areas.

Appendix B (on DVD) shows the one-dimensional (1D) shear wave (Vs) velocity models at

seismic array locations, and the IBC Site Class and Vs100’ (or Vs30m) calculated from these

profiles down to 100 feet using IBC equation 16-41 (Table 2). It is to be noted that additional

criteria as listed in Table 3 must be used when Site Class B is encountered. Site specific

determination by a professional engineer might be required to make sure it can be classified as a

Site Class B site.

Appendix C (on DVD) GIS referenced shapefile map showing the Vs100’, Vs20’ and Vs10’

values representing the average velocities calculated using IBC equation 16-41 (Table 2) for the

top 100’, 20’ and 10’ for all Clark County seismic array lines.


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Figure 35: Clark County and the surrounding valleys with all seismic array lines to date. Lines shown in green were

part of the contract areas for the City of Henderson. Red boxed areas outline the regions shown in Figures 36(a) to

36(e).

Figure 36(a): Las Vegas Valley with all seismic array lines to date. Lines shown in green were part of the contract

areas for the City of Henderson.

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Figure 36(b): The I15 southern corridor including Jean and Primm with all seismic array lines to date. Lines shown

in green were part of the contract areas for the City of Henderson.

Figure 36(c): Coyote Springs with all seismic array lines to date.

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Figure 36(d): Moapa Valley, Longdale, and Overton with all seismic array lines to date.

Figure36(e): Laughlin with all seismic array lines to date.

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6.0 Other Deliverables

In addition to the maps and one dimensional model shown in the Appendices, the following were

posted on Optim SDS secure FTP site for Clark County personnel to download:

GIS referenced shapefile map showing the 100’ average velocities as per IBC 2006

section 1613.5.5. This can be imported into ArcGIS to plot and visualize the values

(Appendix C, on DVD).

Text files showing the velocity profile down to 100 feet and the IBC value.

Associated slowness-frequency image with Rayleigh-wave dispersion curve picks.

ARC color map showing the 100’ velocities color coded as per IBC

Access to the FTP site has been provided to Clark County personnel.

7.0 Conclusions and Recommendations

The project was completed successfully for Clark County. The Nevada System of Higher

Education (NSHE) via the subcontractor Optim Seismic Data Solutions measured shallow shear-

velocity velocities throughout the approximately 500 square miles of Clark County. This project

was conducted in conjunction with City of Henderson Building Department with the objective of

creating a complete map for the Valley. In all, 9006 individual seismic arrays/lines were

assigned, deployed and spatially located using Geographical Positioning System (GPS) in a

systematic manner in order to maximize the data density coverage of the database within Clark

County.

It is recommended that Clark County personnel use other resources at their disposal to per

determine the form the microzonation map should be disseminated to the public. For example, it

is recommended that overlaying the land parcel layer would provide valuable information on

how to classify parcels as per the microzonation (Site Class) map. If the microzonation map

overlay shows two different site class for the same parcel, it is recommended the more

conservative value be used as the default site class for that parcel. It is also to be noted that Site

Class B values in the microzonation map shown in Appendix C is based purely on the Vs100’

value. IBC 2006 Section 1613.5.5 states that: The rock categories, Site Classes A and B, shall

not be used if there is more than 10 feet (3048 mm) of soil between the rock surface and the

bottom of the spread footing or mat foundation. So, when the values suggest a B, site specific

consideration should be made (depth of foundation, competency of rock etc) before deciding

whether it is a Site Class B.

8.0 References

Building Seismic Safety Council, BSSC, 1997, NEHRP Recommended Provisions for Seismic

Regulations for New Buildings and other Structures, Part1 – Provisions, Federal Emergency

Management Agency, Washington D.C., and FEMA 302.

International Building Code, 2006, International Code Council, pages 679.

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Iwata, T., Kawase, H., Satoh, T., Kakehi, Y., Irikura, K., Louie, J. N., Abbott, R. E., and

Anderson, J. G., 1998, Array microtremor measurements at Reno, Nevada, USA (abstract):

Eos, Trans. Amer. Geophysical. Union, v. 79, suppl. to no. 45, p. F578.

Louie, J, N., 2001, Faster, Better: Shear-wave velocity to 100 meters depth from refraction

microtremor arrays: Bulletin of the Seismological Society of America, v. 91, p. 347-364.

Saito, M., 1979, Computations of reflectivity and surface wave dispersion curves for layered

media; I, Sound wave and SH wave: Butsuri-Tanko, v. 32, no. 5, p. 15-26.

Saito, M., 1988, Compound matrix method for the calculation of spheroidal oscillation of the

Earth: Seismol. Res. Lett., v. 59, p. 29.

Stephenson, W. J., J. N. Louie, S. Pullammanappallil, R. A. Williams, and J. K. Odum, (2005).

Blind shear-wave velocity comparison of ReMi and MASW results with boreholes to 200 m

in Santa Clara Valley: Implications for earthquake ground motion assessment, Bulletin of the

Seismological Society of America, 95, 2506-2516, doi: 10.1785/0120040240.

Thelen, W. A., M. Clark, C. T. Lopez, C. Loughner, H. Park, J. B. Scott, S. B. Smith, B.

Greschke, and J. N. Louie (2006). A transect of 200 shallow shear-velocity profiles across the

Los Angeles basin, Bulletin of the Seismological Society of America, 96, 1055-1067.

Xia, J., Miller, R. D., and Park, C. B., 1999, Estimation of near-surface shear-wave velocity by

inversion of Rayleigh wave: Geophysics, v. 64, p. 691-700.

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0090420 0313421 0412107 0412108 0412110a 0412110b 0412116 0412122

0412126 0412127 0420302 0420307 0420315 0702402 0713023 1220201 1220206 1220212 1220332

1220421 1220916 1220922 1221023 1221025 1221101

1221104 1221105 1221107 1221111 1221123

1221505 1221516 1221602 1221610 1221622 1222010 1222101 1222214 1222234

1222236 1222310 1222332 1250201 1250426 1251001 1251006 1251009

1251010 1251011 1251012 1251018 1251021 1251026 1253408 1253409 1253422 1253426 1253612

1253613 1253616 1253627 1253628 1260306 1260328

1260412 1260426 1260812 1260830 1260904

1261001 1261009 1261207 1261219 1261229 1261230 1261307 1261311 1261314

1261403 1261415 1261801 1262210 1262228 1262234 1262703 1262717

1262735 1263410 1263417 1263419 1263420 1263427 1263428 1263429 1263435 1263502 1263518

1263521 1263523 1263527 1263531 1263533 1263632

1263636 1380107 1380110 1380111 1380116

1380619 1380620 1380714 1380722 1381605 1381614 1381616 1381617 1381631

1381633 1381634 1381706 1381708 1381729 1381732 1381733 1381814

1381819 1381824 1381826 1381828 1381906 1381910 1381916 1381917 1381926 1381936 1382003

1382007 1382010 1382016 1382022 1382027 1382030

1382031 1382035 1382107 1382108 1382115

1382116 1382118 1382121 1382129 1382131 1382133 1382136 1382312 1382511

of 66

1382528 1382601 1382604 1382611 1382702 1382805 1382813 1382814 1382908 1382920 1382931

1383002 1383011 1383012 1383013 1383020 1383024 1383025 1383026 1383027 1383031 1383033

1383107 1383113 1383116 1383119 1383215 1383217 1383226 1383333 1383336

1383610 1383622 1401534

1402210 1402334 1402335 1402424 1402425 1402601 1402609 1402613 1402626

1402811 1403503 1403511 1403514 1403523 1403526 1403535 1601917 1601925 1602801 1602902

1602904 1602908 1602912 1602922 1602927 1603022 1603026 1610105 1610107 1610109 1610121

1610129 1610130 1610133 1610134 1610426 1610429b 1610909 1611233 1611313

1611315 1611328 1611435

1611523a 1611525 1611636 1611712a 1611814a 1611915 1612127a 1612231a 1612412

1612515 1612523 1612826 1613023a 1613406a 1621020 1621022 1621023 1621028 1621220 1621616

1621627 1621703 1621704 1621713 1622002 1622006 1622010 1622034 1622207 1630526 1630816

1630821 1632208 1632711 1632808 1633129 1640111 1640131 1640208 1640216

1640219 1640226 1640306

1640307 1640401 1640410 1640411 1641102 1641104 1641106 1641108 1641131

1641133 1641207 1641211 1641219 1641229 1641235 1641315 1641404 1641405 1641409 1641411

1641414 1641415 1641417 1641420 1641422 1641424 1641425 1641427 1641429 1641431 1641432

1642214 1642223 1642231 1642302 1642308 1642311 1642316 1642318 1642321

1642323 1642325 1642328

1642333 1642405 1642407 1642409 1642413 1642416 1642424 1642427 1642429

of 66

1642430 1642435 1642509 1642510 1642519 1642520 1642525 1642529 1643601 1643604 1643611

1643623 1643635 1751301 1751305 1751309 1751311 1751404 1751407 1751420 1751432 1751501

1751512 1751523 1751524 1751526 1751534 1751607 1751609 1751621 1751626

1751633 1752405 1752406

1752410 1760632 1761022 1762026 1763104 1763231 1763234 1763535 1770234

1770330 1771123 1771125 1771316a 1773619 1773634 1910521 1910602 1910611 1910615 1910617

1910618 1910619 1910620 1910621 1910633 1910636 1910718 1910720 1910728 1910734 1911710

1911802 1911810 1911812 1920210 1922401 1923608 1923610 1923614 1923616

1923621 1923629 2040106

2040110 2040213 2040235 2041001 2041013 2041020 2041026 2041112 2041202

2041234 2041415 2041416 2041421 2041623 2043002 2043126 2043219 2160511 2160519 2160612

2160624 2160706 2160719 2160728 2160729 2160818 2160819 2163011 2163023 2171224 2172531

2173605 2173606 2173614 2173618 2231315 2232931 2370814 2640116 2640131

2640226 2641018 2641126

2641307 2641512 2642108 2642132 2642225 2642231 2642308 2642320 2642419

2642505 2642517 2642607 2642621 2642622 2642702 2642714 2642718 2642722 2642730

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