The ANSS event ID is nc40204628 and the event page is at https://earthquake.usgs.gov/earthquakes/eventpage/nc40204628/executive.
2007/10/31 03:04:54 37.434 -121.774 9.7 5.45 California
USGS/SLU Moment Tensor Solution
ENS 2007/10/31 03:04:54:0 37.43 -121.77 9.7 5.4 California
Stations used:
BK.BDM BK.CMB BK.CVS BK.FARB BK.HOPS BK.JCC BK.JRSC BK.KCC
BK.MCCM BK.MNRC BK.ORV BK.PKD BK.SAO BK.WDC BK.WENL BK.YBH
CI.CHF CI.CWC CI.DEC CI.DJJ CI.EDW2 CI.FUR CI.GRA CI.GSC
CI.ISA CI.LRL CI.MLAC CI.MPM CI.MPP CI.MWC CI.PASC CI.PHL
CI.RCT CI.SBC CI.SCZ2 CI.SHO CI.SLA CI.SMM CI.TIN CI.VCS
CI.VES G.SCZ IM.NV31 LB.BMN LB.TPH NN.PAH NN.WCN TA.LAVA
TA.M02C TA.M07A TA.M08A TA.N02C TA.N06A TA.N07B TA.N08A
TA.N09A TA.O01C TA.O06A TA.O07A TA.O08A TA.P06A TA.P07A
TA.P09A TA.Q07A TA.Q08A TA.Q09A TA.Q10A TA.R04C TA.R06C
TA.R08A TA.R09A TA.R10A TA.S05C TA.S09A TA.S10A TA.S11A
TA.T06C TA.U04C TA.U05C TA.U10A TA.V03C US.TPNV XQ.ME05
XQ.ME34 XQ.ME36 XQ.ME43 XQ.ME44 XQ.ME45 XQ.ME46 XQ.ME47
XQ.ME48 XQ.ME49 XQ.ME50 XQ.ME53 XQ.ME54 XQ.ME81 XQ.ME84
XQ.ME92 XQ.ME93
Filtering commands used:
cut o DIST/3.3 -40 o DIST/3.3 +50
rtr
taper w 0.1
hp c 0.03 n 3
lp c 0.06 n 3
Best Fitting Double Couple
Mo = 2.02e+24 dyne-cm
Mw = 5.47
Z = 16 km
Plane Strike Dip Rake
NP1 235 80 -15
NP2 328 75 -170
Principal Axes:
Axis Value Plunge Azimuth
T 2.02e+24 3 282
N 0.00e+00 72 22
P -2.02e+24 18 191
Moment Tensor: (dyne-cm)
Component Value
Mxx -1.68e+24
Mxy -7.41e+23
Mxz 5.96e+23
Myy 1.86e+24
Myz -4.24e+21
Mzz -1.79e+23
--------------
----------------------
######----------------------
#########---------------------
#############---------------------
###############---------------######
##################----------##########
##################-----###############
T ###################-##################
##################---##################
##################-------#################
###############-----------################
#############--------------###############
##########-----------------#############
########--------------------############
#####-----------------------##########
##-------------------------#########
---------------------------#######
-------------------------#####
--------- -------------###
------ P -------------
-- ---------
Global CMT Convention Moment Tensor:
R T P
-1.79e+23 5.96e+23 4.24e+21
5.96e+23 -1.68e+24 7.41e+23
4.24e+21 7.41e+23 1.86e+24
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20071031030454/index.html
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STK = 235
DIP = 80
RAKE = -15
MW = 5.47
HS = 16.0
The NDK file is 20071031030454.ndk The waveform inversion is preferred.
The following compares this source inversion to those provided by others. The purpose is to look for major differences and also to note slight differences that might be inherent to the processing procedure. For completeness the USGS/SLU solution is repeated from above.
USGS/SLU Moment Tensor Solution
ENS 2007/10/31 03:04:54:0 37.43 -121.77 9.7 5.4 California
Stations used:
BK.BDM BK.CMB BK.CVS BK.FARB BK.HOPS BK.JCC BK.JRSC BK.KCC
BK.MCCM BK.MNRC BK.ORV BK.PKD BK.SAO BK.WDC BK.WENL BK.YBH
CI.CHF CI.CWC CI.DEC CI.DJJ CI.EDW2 CI.FUR CI.GRA CI.GSC
CI.ISA CI.LRL CI.MLAC CI.MPM CI.MPP CI.MWC CI.PASC CI.PHL
CI.RCT CI.SBC CI.SCZ2 CI.SHO CI.SLA CI.SMM CI.TIN CI.VCS
CI.VES G.SCZ IM.NV31 LB.BMN LB.TPH NN.PAH NN.WCN TA.LAVA
TA.M02C TA.M07A TA.M08A TA.N02C TA.N06A TA.N07B TA.N08A
TA.N09A TA.O01C TA.O06A TA.O07A TA.O08A TA.P06A TA.P07A
TA.P09A TA.Q07A TA.Q08A TA.Q09A TA.Q10A TA.R04C TA.R06C
TA.R08A TA.R09A TA.R10A TA.S05C TA.S09A TA.S10A TA.S11A
TA.T06C TA.U04C TA.U05C TA.U10A TA.V03C US.TPNV XQ.ME05
XQ.ME34 XQ.ME36 XQ.ME43 XQ.ME44 XQ.ME45 XQ.ME46 XQ.ME47
XQ.ME48 XQ.ME49 XQ.ME50 XQ.ME53 XQ.ME54 XQ.ME81 XQ.ME84
XQ.ME92 XQ.ME93
Filtering commands used:
cut o DIST/3.3 -40 o DIST/3.3 +50
rtr
taper w 0.1
hp c 0.03 n 3
lp c 0.06 n 3
Best Fitting Double Couple
Mo = 2.02e+24 dyne-cm
Mw = 5.47
Z = 16 km
Plane Strike Dip Rake
NP1 235 80 -15
NP2 328 75 -170
Principal Axes:
Axis Value Plunge Azimuth
T 2.02e+24 3 282
N 0.00e+00 72 22
P -2.02e+24 18 191
Moment Tensor: (dyne-cm)
Component Value
Mxx -1.68e+24
Mxy -7.41e+23
Mxz 5.96e+23
Myy 1.86e+24
Myz -4.24e+21
Mzz -1.79e+23
--------------
----------------------
######----------------------
#########---------------------
#############---------------------
###############---------------######
##################----------##########
##################-----###############
T ###################-##################
##################---##################
##################-------#################
###############-----------################
#############--------------###############
##########-----------------#############
########--------------------############
#####-----------------------##########
##-------------------------#########
---------------------------#######
-------------------------#####
--------- -------------###
------ P -------------
-- ---------
Global CMT Convention Moment Tensor:
R T P
-1.79e+23 5.96e+23 4.24e+21
5.96e+23 -1.68e+24 7.41e+23
4.24e+21 7.41e+23 1.86e+24
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20071031030454/index.html
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October 31, 2007, SAN FRANCISCO BAY AREA, CAL, MW=5.6
Goran Ekstrom
Meredith Nettles
CENTROID-MOMENT-TENSOR SOLUTION
GCMT EVENT: C200710310304A
DATA: IU II CU IC GE
L.P.BODY WAVES: 49S, 85C, T= 40
MANTLE WAVES: 15S, 15C, T=125
SURFACE WAVES: 50S, 104C, T= 50
TIMESTAMP: Q-20071031072823
CENTROID LOCATION:
ORIGIN TIME: 03:04:59.7 0.2
LAT:37.44N 0.02;LON:121.78W 0.02
DEP: 15.2 1.0;TRIANG HDUR: 1.5
MOMENT TENSOR: SCALE 10**24 D-CM
RR=-0.330 0.054; TT=-2.270 0.053
PP= 2.600 0.059; RT= 0.553 0.183
RP= 0.496 0.160; TP= 0.947 0.050
PRINCIPAL AXES:
1.(T) VAL= 2.887;PLG=11;AZM=282
2.(N) -0.344; 74; 52
3.(P) -2.543; 12; 189
BEST DBLE.COUPLE:M0= 2.71*10**24
NP1: STRIKE=326;DIP=74;SLIP=-179
NP2: STRIKE=235;DIP=89;SLIP= -16
-----------
-------------------
#####------------------
#########------------------
############--------------###
###############----------######
##############------#########
T ################-#############
##############---#############
###############------############
############----------###########
#########-------------#########
######-----------------########
##---------------------######
----------------------#####
-------- ----------##
------ P ----------
-- ------
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UCB Seismological Laboratory
Inversion method: complete waveform
Stations used: CMB MCCM ORV PKD RO4C SO5C
Berkeley Moment Tensor Solution
Best Fitting Double-Couple:
Mo = 2.05E+24 Dyne-cm
Mw = 5.48
Z = 14
Plane Strike Rake Dip
NP1 146 -178 89
NP2 56 -1 88
Principal Axes:
Axis Value Plunge Azimuth
T 2.049 1 281
N 0.000 88 173
P -2.049 2 11
Event Date/Time: October 31, 2007, 03:04:54.82 UTC
Event ID: nc40204628
Moment Tensor: Scale = 10**24 Dyne-cm
Component Value
Mxx -1.898
Mxy -0.766
Mxz -0.070
Myy 1.900
Myz -0.039
Mzz -0.002
------ P
------------ ----
#------------------------
####-------------------------
########-------------------------
##########------------------------#
############--------------------#####
##############-----------------########
###############------------###########
T ################---------##############
#################-----#################
####################-####################
###################--####################
################-------##################
############-----------################
#########---------------###############
#####--------------------############
#------------------------##########
-------------------------########
------------------------#####
------------------------#
-------------------
-------
Lower Hemisphere Equiangle Projection
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Given the availability of digital waveforms for determination of the moment tensor, this section documents the added processing leading to mLg, if appropriate to the region, and ML by application of the respective IASPEI formulae. As a research study, the linear distance term of the IASPEI formula for ML is adjusted to remove a linear distance trend in residuals to give a regionally defined ML. The defined ML uses horizontal component recordings, but the same procedure is applied to the vertical components since there may be some interest in vertical component ground motions. Residual plots versus distance may indicate interesting features of ground motion scaling in some distance ranges. A residual plot of the regionalized magnitude is given as a function of distance and azimuth, since data sets may transcend different wave propagation provinces.
Left: ML computed using the IASPEI formula for Horizontal components. Center: ML residuals computed using a modified IASPEI formula that accounts for path specific attenuation; the values used for the trimmed mean are indicated. The ML relation used for each figure is given at the bottom of each plot.
Right: Residuals from new relation as a function of distance and azimuth.
Left: ML computed using the IASPEI formula for Vertical components (research). Center: ML residuals computed using a modified IASPEI formula that accounts for path specific attenuation; the values used for the trimmed mean are indicated. The ML relation used for each figure is given at the bottom of each plot.
Right: Residuals from new relation as a function of distance and azimuth.
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The focal mechanism was determined using broadband seismic waveforms. The location of the event (star) and the stations used for (red) the waveform inversion are shown in the next figure.
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The program wvfgrd96 was used with good traces observed at short distance to determine the focal mechanism, depth and seismic moment. This technique requires a high quality signal and well determined velocity model for the Green's functions. To the extent that these are the quality data, this type of mechanism should be preferred over the radiation pattern technique which requires the separate step of defining the pressure and tension quadrants and the correct strike.
The observed and predicted traces are filtered using the following gsac commands:
cut o DIST/3.3 -40 o DIST/3.3 +50 rtr taper w 0.1 hp c 0.03 n 3 lp c 0.06 n 3The results of this grid search are as follow:
DEPTH STK DIP RAKE MW FIT
WVFGRD96 1.0 235 65 15 5.09 0.1996
WVFGRD96 2.0 60 75 40 5.23 0.2628
WVFGRD96 3.0 235 60 10 5.24 0.2935
WVFGRD96 4.0 230 80 -15 5.26 0.3183
WVFGRD96 5.0 230 75 -15 5.29 0.3400
WVFGRD96 6.0 235 80 -15 5.30 0.3594
WVFGRD96 7.0 235 80 -15 5.33 0.3794
WVFGRD96 8.0 235 80 -20 5.36 0.3976
WVFGRD96 9.0 235 80 -20 5.38 0.4122
WVFGRD96 10.0 235 80 -20 5.40 0.4237
WVFGRD96 11.0 235 80 -20 5.41 0.4331
WVFGRD96 12.0 235 80 -20 5.42 0.4401
WVFGRD96 13.0 235 80 -20 5.44 0.4449
WVFGRD96 14.0 235 80 -20 5.45 0.4476
WVFGRD96 15.0 235 80 -15 5.46 0.4493
WVFGRD96 16.0 235 80 -15 5.47 0.4494
WVFGRD96 17.0 235 80 -15 5.48 0.4486
WVFGRD96 18.0 235 80 -15 5.49 0.4466
WVFGRD96 19.0 235 80 -15 5.50 0.4438
WVFGRD96 20.0 235 80 -15 5.51 0.4396
WVFGRD96 21.0 235 80 -20 5.52 0.4348
WVFGRD96 22.0 235 80 -20 5.53 0.4290
WVFGRD96 23.0 235 80 -20 5.53 0.4223
WVFGRD96 24.0 235 80 -20 5.54 0.4150
WVFGRD96 25.0 235 80 -20 5.55 0.4072
WVFGRD96 26.0 235 75 -15 5.55 0.3992
WVFGRD96 27.0 235 75 -15 5.56 0.3911
WVFGRD96 28.0 235 75 -15 5.57 0.3828
WVFGRD96 29.0 235 75 -15 5.57 0.3742
The best solution is
WVFGRD96 16.0 235 80 -15 5.47 0.4494
The mechanism corresponding to the best fit is
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The best fit as a function of depth is given in the following figure:
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The comparison of the observed and predicted waveforms is given in the next figure. The red traces are the observed and the blue are the predicted. Each observed-predicted component is plotted to the same scale and peak amplitudes are indicated by the numbers to the left of each trace. A pair of numbers is given in black at the right of each predicted traces. The upper number it the time shift required for maximum correlation between the observed and predicted traces. This time shift is required because the synthetics are not computed at exactly the same distance as the observed, the velocity model used in the predictions may not be perfect and the epicentral parameters may be be off. A positive time shift indicates that the prediction is too fast and should be delayed to match the observed trace (shift to the right in this figure). A negative value indicates that the prediction is too slow. The lower number gives the percentage of variance reduction to characterize the individual goodness of fit (100% indicates a perfect fit).
The bandpass filter used in the processing and for the display was
cut o DIST/3.3 -40 o DIST/3.3 +50 rtr taper w 0.1 hp c 0.03 n 3 lp c 0.06 n 3
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| Figure 3. Waveform comparison for selected depth. Red: observed; Blue - predicted. The time shift with respect to the model prediction is indicated. The percent of fit is also indicated. The time scale is relative to the first trace sample. |
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| Focal mechanism sensitivity at the preferred depth. The red color indicates a very good fit to the waveforms. Each solution is plotted as a vector at a given value of strike and dip with the angle of the vector representing the rake angle, measured, with respect to the upward vertical (N) in the figure. |
A check on the assumed source location is possible by looking at the time shifts between the observed and predicted traces. The time shifts for waveform matching arise for several reasons:
Time_shift = A + B cos Azimuth + C Sin Azimuth
The time shifts for this inversion lead to the next figure:
The derived shift in origin time and epicentral coordinates are given at the bottom of the figure.
The following figure shows the stations used in the grid search for the best focal mechanism to fit the surface-wave spectral amplitudes of the Love and Rayleigh waves.
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The surface-wave determined focal mechanism is shown here.
NODAL PLANES
STK= 59.99
DIP= 80.00
RAKE= 29.99
OR
STK= 324.26
DIP= 60.51
RAKE= 168.49
DEPTH = 11.0 km
Mw = 5.54
Best Fit 0.8679 - P-T axis plot gives solutions with FIT greater than FIT90
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Surface wave analysis was performed using codes from Computer Programs in Seismology, specifically the multiple filter analysis program do_mft and the surface-wave radiation pattern search program srfgrd96.
Digital data were collected, instrument response removed and traces converted
to Z, R an T components. Multiple filter analysis was applied to the Z and T traces to obtain the Rayleigh- and Love-wave spectral amplitudes, respectively.
These were input to the search program which examined all depths between 1 and 25 km
and all possible mechanisms.
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| Pressure-tension axis trends. Since the surface-wave spectra search does not distinguish between P and T axes and since there is a 180 ambiguity in strike, all possible P and T axes are plotted. First motion data and waveforms will be used to select the preferred mechanism. The purpose of this plot is to provide an idea of the possible range of solutions. The P and T-axes for all mechanisms with goodness of fit greater than 0.9 FITMAX (above) are plotted here. |
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| Focal mechanism sensitivity at the preferred depth. The red color indicates a very good fit to the Love and Rayleigh wave radiation patterns. Each solution is plotted as a vector at a given value of strike and dip with the angle of the vector representing the rake angle, measured, with respect to the upward vertical (N) in the figure. Because of the symmetry of the spectral amplitude rediation patterns, only strikes from 0-180 degrees are sampled. |
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The WUS.model used for the waveform synthetic seismograms and for the surface wave eigenfunctions and dispersion is as follows (The format is in the model96 format of Computer Programs in Seismology).
MODEL.01
Model after 8 iterations
ISOTROPIC
KGS
FLAT EARTH
1-D
CONSTANT VELOCITY
LINE08
LINE09
LINE10
LINE11
H(KM) VP(KM/S) VS(KM/S) RHO(GM/CC) QP QS ETAP ETAS FREFP FREFS
1.9000 3.4065 2.0089 2.2150 0.302E-02 0.679E-02 0.00 0.00 1.00 1.00
6.1000 5.5445 3.2953 2.6089 0.349E-02 0.784E-02 0.00 0.00 1.00 1.00
13.0000 6.2708 3.7396 2.7812 0.212E-02 0.476E-02 0.00 0.00 1.00 1.00
19.0000 6.4075 3.7680 2.8223 0.111E-02 0.249E-02 0.00 0.00 1.00 1.00
0.0000 7.9000 4.6200 3.2760 0.164E-10 0.370E-10 0.00 0.00 1.00 1.00