seismic waves and earthquake location
DESCRIPTION
Seismic Waves and Earthquake Location. Walter D. Mooney US Geological Survey California Mooney @ usgs.gov. Wave propagation animation. Seismogram showing different phases. SEISMIC WAVE VELOCITY. Body Waves. P-wave. Vp ~ √3 Vs. S-wave. Surface Waves. - PowerPoint PPT PresentationTRANSCRIPT
Seismic Waves Seismic Waves and and
Earthquake LocationEarthquake Location
Walter D. MooneyUS Geological Survey
CaliforniaMooney @ usgs.gov
SEISMIC WAVE VELOCITYSEISMIC WAVE VELOCITY
Body Waves
P-wave
S-wave
Surface Waves
Love Wave V S1 < VL< V S2
Rayleigh Wave VR < 0.92 VS
2
1
2
pV
2
1
Vs
Vp ~ √3 Vs.
Conversion of Seismic Phases at Rock BoundariesConversion of Seismic Phases at Rock Boundaries
Sini
Sinr
V
V2
1
2
T-phase of the Largest Aftershock of the 2004 Sumatra Earthquake Recorded at the VISK Station, India
EARTHQUAKE LOCATION EARTHQUAKE LOCATION
Manual Method for Location
Single-station Location
Multi-station Location
Computational Methods for Location
Computer Programs for Location
HYPO 71
SEISAN
Manual Method
C
SEISMIC STATION
A
* EPICENTRE
D
B
EPICENTRE
HYPOCENTRE
H
*
CHAPTER 3 FIG. 28 a
X SEISMOGRAPHSTATION
D Ts Tp 8
Ts Tp DVs Vp
1 1
Computational Method
Input data: P & S Arrival Data
Station Coordinates
Station Correction
P-wave Velocity Model
Vp/Vs
Maximum Amplitude
Signal Duration
Geiger's (1912) method of least squares Technique
Computation :
Ri = i - t i RMS
N
ii
N
R
2
1
1
CHAPTER 3 FIG. 34
A
CHAPTER 3 FIG. 35
B
(a) Earthquake occurs in a Circular Array
(b) Earthqauke occurs outside the Array
Note: At least one S-phase is required to control the Hypocentre location
Limitations in Precise Location:
EARTHQUAKE RELOCATION
Master Event Method
Average Residual Method
Homogeneous Station Method
Double-Difference (DD) Method
Joint Hypocentre Method
rij = tij – (ij + Si)
caljk
ik
obsjk
ik
ijk ttttdr )()(