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Coherence-weighted Wavepath Coherence-weighted Wavepath Migration for Teleseismic Data Migration for Teleseismic Data
J. Sheng, G. T. Schuster, K. L. Pankow, J. Sheng, G. T. Schuster, K. L. Pankow, J. C. Pechmann, and R. L. Nowack J. C. Pechmann, and R. L. Nowack
University of UtahUniversity of Utah
Feb. 5, 2004Feb. 5, 2004
MotivationMotivation
Given: Teleseismic dataGiven: Teleseismic dataGoal: Local crustal structureGoal: Local crustal structure
Solution I: Receiver function (RF)Solution I: Receiver function (RF)
Principle of RFPrinciple of RF
(Langston, 1977, 1979)(Langston, 1977, 1979)
PP
PPPSPS
MohoMoho
P
Ps
Ps
P
G
G
V
R
iGsR
iGsV
Vertical Comp.Vertical Comp.
RadialRadial
Source historySource historyGreen’s fun.Green’s fun.
InstrumentInstrument
ProblemsProblems
• Other phases generate artifactsOther phases generate artifacts
MohoMoho
pPspPs pSspSs pPppPp
MotivationMotivation
Given: teleseismic dataGiven: teleseismic dataGoal: local crustal structureGoal: local crustal structure
Solution I: Receiver function (RF)Solution I: Receiver function (RF)
Solution II: Xcorrelogram mig. (Xmig)Solution II: Xcorrelogram mig. (Xmig)
Principle of XmigPrinciple of Xmig
GhostGhostP-waveP-wave
Direct Direct P-waveP-wave
ProblemsProblems
• Incident angle usually > 30 deg.Incident angle usually > 30 deg.• Irregular spacing Irregular spacing • Low frequency and long source Low frequency and long source historyhistory
MotivationMotivation
Given: teleseismic dataGiven: teleseismic dataGoal: local crustal structureGoal: local crustal structure
Solution I: Receiver function (RF)Solution I: Receiver function (RF)
Solution II: Xcorrelogram mig. (Xmig)Solution II: Xcorrelogram mig. (Xmig)
Solution III: Coherence-weighted WM Solution III: Coherence-weighted WM
Coherence-weighted WMCoherence-weighted WM
OutlineOutline
Synthetic TestSynthetic Test
Earthquake DataEarthquake Data
SummarySummary
Coherence-weighted WM Coherence-weighted WM
Step 1:Step 1: Calculate radial and vertical RFCalculate radial and vertical RF
a.a. zero-phase traces zero-phase traces vvv *
b. source wavelet b. source wavelet vN
s1
c. deconvolution c. deconvolution s
v'
Coherence-weighted WM Coherence-weighted WM
Step 2:Step 2: Migrate RF and obtain Migrate RF and obtain ps, pPs, and pPp imagesps, pPs, and pPp images
Step 1:Step 1: Calculate radial and vertical RFCalculate radial and vertical RF
Wavepath MigrationWavepath Migration
Plane wavePlane wave
MMpsps(x)=RRF(T(x)=RRF(TSS-T-TPP))
RR
X’X’XX
X’X’XX
X’X’XX
PP
SS
MMpPspPs(x)=RRF(T(x)=RRF(TSS+T+TPP))
MMpPppPp(x)=VRF(2T(x)=VRF(2TPP))
Coherence-weighted WM Coherence-weighted WM
Step 2:Step 2: Migrate RF and obtain Migrate RF and obtain ps, pPs, and pPp imagesps, pPs, and pPp images
Step 1:Step 1: Calculate radial and vertical RFCalculate radial and vertical RF
Step 3:Step 3: Coherence weight Coherence weight
Coherence-weighted WM Coherence-weighted WM
MMCWCW=W*Mps=W*Mps
00
606000 220220
Dep
th (
km)
Dep
th (
km)
Distances (km)Distances (km)
psps pPspPs pPppPp
00 220220Distances (km)Distances (km)00 220220Distances (km)Distances (km)
00
6060
Dep
th (
km)
Dep
th (
km)
00 220220Distances (km)Distances (km)
Coherence-weighted WMCoherence-weighted WM
OutlineOutline
Synthetic TestSynthetic Test
Earthquake DataEarthquake Data
SummarySummary
00
606000 220220
Dep
th (
km
)D
epth
(k
m)
Distances (km)Distances (km)
Synthetic ModelSynthetic Model
Parameters (Synthetic)Parameters (Synthetic)
• Plane P-wave incident at 40 deg.Plane P-wave incident at 40 deg.• 221 Stations with 1km spacing 221 Stations with 1km spacing • Source peak frequency 0.6 Hz Source peak frequency 0.6 Hz
00
7070
Synthetic SeismogramSynthetic SeismogramT
rave
ltim
e (s
ec.)
Tra
velt
ime
(sec
.)
VerticalVertical RadialRadial
00
2020
Tra
velt
ime
(sec
.)T
rave
ltim
e (s
ec.)
Radial RF (Synthetic)Radial RF (Synthetic)
00
2020
Tra
velt
ime
(sec
.)T
rave
ltim
e (s
ec.)
Vertical RF (Synthetic)Vertical RF (Synthetic)
ps Image (Synthetic)ps Image (Synthetic)
00
606000 220220
Dep
th (
km
)D
epth
(k
m)
Distances (km)Distances (km)
pPs Image (Synthetic)pPs Image (Synthetic)
00
606000 220220
Dep
th (
km
)D
epth
(k
m)
Distances (km)Distances (km)
pPp Image (Synthetic)pPp Image (Synthetic)
00
606000 220220
Dep
th (
km
)D
epth
(k
m)
Distances (km)Distances (km)
CW Image (Synthetic)CW Image (Synthetic)
00
606000 220220
Dep
th (
km
)D
epth
(k
m)
Distances (km)Distances (km)
Coherence-weighted WMCoherence-weighted WM
OutlineOutline
Synthetic TestSynthetic Test
Earthquake DataEarthquake Data
SummarySummary
Earthquake Data Earthquake Data
Great Salt Lake
Great Salt Lake
41.841.8
39.839.8
-113.5-113.5 -110.5-110.5
Lat
itu
de
(deg
.)L
atit
ud
e (d
eg.)
Longitude (deg.)Longitude (deg.)
Station MapStation Map
Processing ParametersProcessing Parameters
120120
5050
270270
200200Tim
e (s
ec.)
Tim
e (s
ec.)
50 sec.50 sec.
50 sec.50 sec.
Passband:Passband:0.2~0.6 Hz0.2~0.6 Hz
Water-level:Water-level:0.0010.001
Radial RF Radial RF
00
202000 200200
Tim
e (s
ec.)
Tim
e (s
ec.)
Distances (km)Distances (km)
00
202000 200200
Tim
e (s
ec.)
Tim
e (s
ec.)
Distances (km)Distances (km)
Vertical RF Vertical RF
00
606000 200200
Dep
th (
km
)D
epth
(k
m)
Distances (km)Distances (km)
ps Image ps Image
00
606000 200200
Dep
th (
km
)D
epth
(k
m)
Distances (km)Distances (km)
pPs Image pPs Image
00
606000 200200
Dep
th (
km
)D
epth
(k
m)
Distances (km)Distances (km)
pPp Image pPp Image
00
606000 200200
Dep
th (
km
)D
epth
(k
m)
Distances (km)Distances (km)
CW Image CW Image
Coherence-weighted WMCoherence-weighted WM
OutlineOutline
Synthetic TestSynthetic Test
Earthquake DataEarthquake Data
SummarySummary
SummarySummary
• ps, pPs, and pPp arrivals in RF can be migrated ps, pPs, and pPp arrivals in RF can be migrated to provide a different perspective. to provide a different perspective.
• CWWM can combine three images to correctly CWWM can combine three images to correctly image the reflector with attenuated artifacts. image the reflector with attenuated artifacts.
• This method can image the Moho at the depth This method can image the Moho at the depth consistent with previous studies. consistent with previous studies.
AcknowledgmentAcknowledgment
I thank the sponsors of the 2003 UTAM I thank the sponsors of the 2003 UTAM Consortium for their financial support . Consortium for their financial support .