The ANSS event ID is nn00349954 and the event page is at https://earthquake.usgs.gov/earthquakes/eventpage/nn00349954/executive.
2011/10/01 07:07:01 38.897 -118.766 3.9 4.8 Nevada
USGS/SLU Moment Tensor Solution ENS 2011/10/01 07:07:01:0 38.90 -118.77 3.9 4.8 Nevada Stations used: BK.CMB BK.HUMO BK.MOD BK.SAO BK.WDC BK.YBH CI.GSC CI.ISA CI.LDF CI.MWC CI.OSI CI.PASC LB.BMN LB.DAC NC.AFD NC.KBO NC.KHMB NC.MDPB NN.BEK NN.PAH NN.PNT NN.RUB NN.TVH1 NN.TVH2 NN.TVH3 NN.VCN UU.BGU UU.LCMT UU.NLU UW.TREE Filtering commands used: hp c 0.02 n 3 lp c 0.06 n 3 Best Fitting Double Couple Mo = 2.04e+22 dyne-cm Mw = 4.14 Z = 10 km Plane Strike Dip Rake NP1 153 80 -165 NP2 60 75 -10 Principal Axes: Axis Value Plunge Azimuth T 2.04e+22 4 286 N 0.00e+00 72 184 P -2.04e+22 18 17 Moment Tensor: (dyne-cm) Component Value Mxx -1.55e+22 Mxy -1.05e+22 Mxz -5.26e+21 Myy 1.73e+22 Myz -2.97e+21 Mzz -1.77e+21 ----------- ##------------- P ---- #####------------- ------- #######----------------------- #########------------------------- ###########------------------------- ############------------------------## ############---------------------##### T #############------------------####### ##############---------------########## ##################-----------############# ###################--------############### ####################----################## ######################################## ################-----################### ##########-----------################# ##-------------------############### ---------------------############# ---------------------######### ---------------------####### --------------------## -------------- Global CMT Convention Moment Tensor: R T P -1.77e+21 -5.26e+21 2.97e+21 -5.26e+21 -1.55e+22 1.05e+22 2.97e+21 1.05e+22 1.73e+22 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20111001070701/index.html |
STK = 60 DIP = 75 RAKE = -10 MW = 4.14 HS = 10.0
The NDK file is 20111001070701.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 2011/10/01 07:07:01:0 38.90 -118.77 3.9 4.8 Nevada Stations used: BK.CMB BK.HUMO BK.MOD BK.SAO BK.WDC BK.YBH CI.GSC CI.ISA CI.LDF CI.MWC CI.OSI CI.PASC LB.BMN LB.DAC NC.AFD NC.KBO NC.KHMB NC.MDPB NN.BEK NN.PAH NN.PNT NN.RUB NN.TVH1 NN.TVH2 NN.TVH3 NN.VCN UU.BGU UU.LCMT UU.NLU UW.TREE Filtering commands used: hp c 0.02 n 3 lp c 0.06 n 3 Best Fitting Double Couple Mo = 2.04e+22 dyne-cm Mw = 4.14 Z = 10 km Plane Strike Dip Rake NP1 153 80 -165 NP2 60 75 -10 Principal Axes: Axis Value Plunge Azimuth T 2.04e+22 4 286 N 0.00e+00 72 184 P -2.04e+22 18 17 Moment Tensor: (dyne-cm) Component Value Mxx -1.55e+22 Mxy -1.05e+22 Mxz -5.26e+21 Myy 1.73e+22 Myz -2.97e+21 Mzz -1.77e+21 ----------- ##------------- P ---- #####------------- ------- #######----------------------- #########------------------------- ###########------------------------- ############------------------------## ############---------------------##### T #############------------------####### ##############---------------########## ##################-----------############# ###################--------############### ####################----################## ######################################## ################-----################### ##########-----------################# ##-------------------############### ---------------------############# ---------------------######### ---------------------####### --------------------## -------------- Global CMT Convention Moment Tensor: R T P -1.77e+21 -5.26e+21 2.97e+21 -5.26e+21 -1.55e+22 1.05e+22 2.97e+21 1.05e+22 1.73e+22 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20111001070701/index.html |
REVIEWED BY NSL STAFF Event ID:349692 Origin ID:838886 Algorithm: Ichinose (2003) Long Period, Regional-Distance Waves Seismic Moment Tensor Solution 2011/10/01 (274) 07:07:02.00 38.8903 -118.7740 001 Depth = 8.0 (km) Mw = 4.13 Mo = 1.95x10^22 (dyne x cm) Percent Double Couple = 92 % Percent CLVD = 8 % no ISO calculated Epsilon=-0.04 Percent Variance Reduction = 84.83 % Total Fit = 8.93 Major Double Couple strike dip rake Nodal Plane 1: 59 71 -14 Nodal Plane 2: 154 76 -161 DEVIATORIC MOMENT TENSOR Moment Tensor Elements: Spherical Coordinates Mrr= -0.36 Mtt= -1.33 Mff= 1.69 Mrt= -0.60 Mrf= 0.32 Mtf= 0.98 EXP=22 Moment Tensor Elements: Cartesian Coordinates -1.33 -0.98 -0.60 -0.98 1.69 -0.32 -0.60 -0.32 -0.36 Eigenvalues: T-axis eigenvalue= 1.99 N-axis eigenvalue= -0.08 P-axis eigenvalue= -1.91 Eigenvalues and eigenvectors of the Major Double Couple: T-axis ev= 1.99 trend=286 plunge=4 N-axis ev= 0.00 trend=188 plunge=66 P-axis ev=-1.99 trend=17 plunge=23 Maximum Azmuithal Gap=67 Distance to Nearest Station= 60.9 (km) Number of Stations (D=Displacement/V=Velocity) Used=21 (defining only) KVN.NN.D WAK.NN.D PNT.NN.D VCN.NN.D PAH.NN.D RUB.NN.D BEK.NN.D TIN.CI.D BMN.LB.D GRA.CI.D R11A.TA.D DAC.LB.D TPNV.US.D HATC.BK.D FUR.CI.D BRK.BK.D LRL.CI.D SHO.CI.D SHP.NN.D TUQ.CI.D L04D.TA.D ------------ -- ####------------ P ------ ######------------ -------- ########------------------------- #########-------------------------- ###########-------------------------- -############-------------------------### ##############----------------------##### T ###############--------------------####### ###############------------------######### #################---------------############ ##################------------############## ###################---------################ ####################-----################### #####################-##################### ########################################### ##################--##################### ############--------#################### ######---------------################## ---------------------############### ---------------------############ ---------------------######## --------------------##### ----------------- All Stations defining and nondefining: Station.Net Def Distance Azi Bazi lo-f hi-f vmodel (km) (deg) (deg) (Hz) (Hz) KVN.NN (D) Y 60.9 73 253 0.020 0.080 KVN.NN.wus.glib WAK.NN (D) Y 72.2 233 53 0.020 0.080 WAK.NN.wus.glib PNT.NN (D) Y 74.7 288 107 0.020 0.080 PNT.NN.wus.glib VCN.NN (D) Y 88.2 301 121 0.020 0.080 VCN.NN.wus.glib PAH.NN (D) Y 105.4 330 150 0.020 0.080 PAH.NN.wus.glib RUB.NN (D) Y 120.2 279 98 0.020 0.080 RUB.NN.wus.glib BEK.NN (D) Y 174.4 309 128 0.020 0.080 BEK.NN.wus.glib TIN.CI (D) Y 210.0 167 347 0.020 0.080 TIN.CI.wus.glib BMN.LB (D) Y 216.6 37 218 0.020 0.080 BMN.LB.wus.glib GRA.CI (D) Y 243.4 149 330 0.020 0.080 GRA.CI.wus.glib R11A.TA (D) Y 282.8 101 283 0.020 0.080 R11A.TA.wus.glib DAC.LB (D) Y 308.2 160 341 0.020 0.080 DAC.LB.wus.glib TPNV.US (D) Y 308.9 133 315 0.020 0.080 TPNV.US.wus.glib HATC.BK (D) Y 313.8 314 132 0.020 0.080 HATC.BK.wus.glib FUR.CI (D) Y 317.2 147 329 0.020 0.080 FUR.CI.wus.glib BRK.BK (D) Y 324.1 251 68 0.020 0.080 BRK.BK.wus.glib LRL.CI (D) Y 391.1 165 346 0.020 0.080 LRL.CI.wus.glib SHO.CI (D) Y 398.5 146 327 0.020 0.080 SHO.CI.wus.glib SHP.NN (D) Y 414.1 129 311 0.020 0.080 SHP.NN.wus.glib TUQ.CI (D) Y 459.1 146 327 0.020 0.080 TUQ.CI.wus.glib L04D.TA (D) Y 474.7 322 140 0.020 0.080 L04D.TA.wus.glib (V)-velocity (D)-Displacement Author: www-data Date: 2011/10/01 10:34:11 mtinv Version 2.1_DEVEL OCT2008 |
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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:
hp c 0.02 n 3 lp c 0.06 n 3The results of this grid search are as follow:
DEPTH STK DIP RAKE MW FIT WVFGRD96 0.5 60 90 -35 4.01 0.4442 WVFGRD96 1.0 245 85 35 4.03 0.4742 WVFGRD96 2.0 245 80 20 4.03 0.5157 WVFGRD96 3.0 60 80 -20 4.06 0.5479 WVFGRD96 4.0 60 75 -20 4.08 0.5767 WVFGRD96 5.0 60 75 -20 4.10 0.5972 WVFGRD96 6.0 60 75 -15 4.11 0.6115 WVFGRD96 7.0 60 75 -15 4.11 0.6200 WVFGRD96 8.0 60 75 -15 4.12 0.6238 WVFGRD96 9.0 60 75 -10 4.13 0.6259 WVFGRD96 10.0 60 75 -10 4.14 0.6274 WVFGRD96 11.0 60 75 -10 4.14 0.6229 WVFGRD96 12.0 60 75 -10 4.15 0.6166 WVFGRD96 13.0 60 75 -10 4.15 0.6086 WVFGRD96 14.0 60 75 -5 4.16 0.6013 WVFGRD96 15.0 60 75 -5 4.16 0.5936 WVFGRD96 16.0 60 75 -5 4.17 0.5860 WVFGRD96 17.0 60 75 5 4.18 0.5839 WVFGRD96 18.0 60 75 5 4.18 0.5812 WVFGRD96 19.0 60 75 5 4.19 0.5785 WVFGRD96 20.0 60 75 5 4.20 0.5750 WVFGRD96 21.0 60 75 5 4.21 0.5701 WVFGRD96 22.0 60 75 5 4.21 0.5649 WVFGRD96 23.0 60 75 5 4.22 0.5590 WVFGRD96 24.0 60 75 5 4.22 0.5528 WVFGRD96 25.0 60 75 10 4.23 0.5464 WVFGRD96 26.0 60 75 10 4.23 0.5400 WVFGRD96 27.0 60 75 10 4.24 0.5333 WVFGRD96 28.0 60 75 10 4.25 0.5266 WVFGRD96 29.0 60 75 10 4.25 0.5199
The best solution is
WVFGRD96 10.0 60 75 -10 4.14 0.6274
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
hp c 0.02 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 CUS.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 CUS Model with Q from simple gamma values 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 1.0000 5.0000 2.8900 2.5000 0.172E-02 0.387E-02 0.00 0.00 1.00 1.00 9.0000 6.1000 3.5200 2.7300 0.160E-02 0.363E-02 0.00 0.00 1.00 1.00 10.0000 6.4000 3.7000 2.8200 0.149E-02 0.336E-02 0.00 0.00 1.00 1.00 20.0000 6.7000 3.8700 2.9020 0.000E-04 0.000E-04 0.00 0.00 1.00 1.00 0.0000 8.1500 4.7000 3.3640 0.194E-02 0.431E-02 0.00 0.00 1.00 1.00