The ANSS event ID is nn00495477 and the event page is at https://earthquake.usgs.gov/earthquakes/eventpage/nn00495477/executive.
2015/05/22 18:47:42 37.292 -114.655 4.0 5.3 Nevada
USGS/SLU Moment Tensor Solution ENS 2015/05/22 18:47:42:0 37.29 -114.65 4.0 5.3 Nevada Stations used: AE.113A AE.U15A AE.W13A AE.X16A AE.Y14A BC.RMX BC.TKX CI.BAR CI.GLA CI.ISA CI.LDF CI.MWC CI.OSI CI.PASC II.PFO IM.NV31 LB.TPH NC.AFD NC.PMPB NN.BEK NN.KVN NN.LHV NN.PAH NN.PNT NN.REDF NN.RUB NN.RYN NN.SHP NN.VCN NN.WAK NN.YER TA.109C TA.R11A TA.W18A US.DUG US.ELK US.HWUT US.MVCO US.TPNV US.WUAZ UU.BGU UU.BRPU UU.CCUT UU.CTU UU.HVU UU.JLU UU.KNB UU.LCMT UU.MPU UU.MTPU UU.NLU UU.PKCU UU.PSUT UU.SPU UU.SRU UU.TCRU UU.TMU UU.VRUT Filtering commands used: cut o DIST/3.3 -30 o DIST/3.3 +70 rtr taper w 0.1 hp c 0.02 n 3 lp c 0.06 n 3 Best Fitting Double Couple Mo = 2.37e+23 dyne-cm Mw = 4.85 Z = 12 km Plane Strike Dip Rake NP1 80 85 -15 NP2 171 75 -175 Principal Axes: Axis Value Plunge Azimuth T 2.37e+23 7 127 N 0.00e+00 74 242 P -2.37e+23 14 35 Moment Tensor: (dyne-cm) Component Value Mxx -6.77e+22 Mxy -2.16e+23 Mxz -6.30e+22 Myy 7.84e+22 Myz -9.16e+21 Mzz -1.07e+22 ####---------- #######--------------- ##########-------------- - ###########-------------- P -- ############--------------- ---- #############----------------------- ##############------------------------ ###############------------------------- ################------------------------ #################----------------------### #################---------------########## #################------################### ###########-------######################## -----------------####################### -----------------####################### -----------------##################### ----------------################ # ----------------############### T ---------------############## --------------############## ------------########## ---------##### Global CMT Convention Moment Tensor: R T P -1.07e+22 -6.30e+22 9.16e+21 -6.30e+22 -6.77e+22 2.16e+23 9.16e+21 2.16e+23 7.84e+22 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20150522184742/index.html |
STK = 80 DIP = 85 RAKE = -15 MW = 4.85 HS = 12.0
The NDK file is 20150522184742.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 2015/05/22 18:47:42:0 37.29 -114.65 4.0 5.3 Nevada Stations used: AE.113A AE.U15A AE.W13A AE.X16A AE.Y14A BC.RMX BC.TKX CI.BAR CI.GLA CI.ISA CI.LDF CI.MWC CI.OSI CI.PASC II.PFO IM.NV31 LB.TPH NC.AFD NC.PMPB NN.BEK NN.KVN NN.LHV NN.PAH NN.PNT NN.REDF NN.RUB NN.RYN NN.SHP NN.VCN NN.WAK NN.YER TA.109C TA.R11A TA.W18A US.DUG US.ELK US.HWUT US.MVCO US.TPNV US.WUAZ UU.BGU UU.BRPU UU.CCUT UU.CTU UU.HVU UU.JLU UU.KNB UU.LCMT UU.MPU UU.MTPU UU.NLU UU.PKCU UU.PSUT UU.SPU UU.SRU UU.TCRU UU.TMU UU.VRUT Filtering commands used: cut o DIST/3.3 -30 o DIST/3.3 +70 rtr taper w 0.1 hp c 0.02 n 3 lp c 0.06 n 3 Best Fitting Double Couple Mo = 2.37e+23 dyne-cm Mw = 4.85 Z = 12 km Plane Strike Dip Rake NP1 80 85 -15 NP2 171 75 -175 Principal Axes: Axis Value Plunge Azimuth T 2.37e+23 7 127 N 0.00e+00 74 242 P -2.37e+23 14 35 Moment Tensor: (dyne-cm) Component Value Mxx -6.77e+22 Mxy -2.16e+23 Mxz -6.30e+22 Myy 7.84e+22 Myz -9.16e+21 Mzz -1.07e+22 ####---------- #######--------------- ##########-------------- - ###########-------------- P -- ############--------------- ---- #############----------------------- ##############------------------------ ###############------------------------- ################------------------------ #################----------------------### #################---------------########## #################------################### ###########-------######################## -----------------####################### -----------------####################### -----------------##################### ----------------################ # ----------------############### T ---------------############## --------------############## ------------########## ---------##### Global CMT Convention Moment Tensor: R T P -1.07e+22 -6.30e+22 9.16e+21 -6.30e+22 -6.77e+22 2.16e+23 9.16e+21 2.16e+23 7.84e+22 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20150522184742/index.html |
Regional Moment Tensor (Mwr) Moment 2.342e+16 N-m Magnitude 4.85 Depth 12.0 km Percent DC 74% Half Duration – Catalog US (us10002blf) Data Source US2 Contributor US2 Nodal Planes Plane Strike Dip Rake NP1 82 86 -14 NP2 173 77 -175 Principal Axes Axis Value Plunge Azimuth T 2.162 6 128 N 0.326 76 244 P -2.488 13 37 |
W-phase Moment Tensor (Mww) Moment 3.006e+16 N-m Magnitude 4.92 Depth 11.5 km Percent DC 56% Half Duration – Catalog US (us10002blf) Data Source US2 Contributor US2 Nodal Planes Plane Strike Dip Rake NP1 262 82 20 NP2 169 70 171 Principal Axes Axis Value Plunge Azimuth T 3.304 20 128 N -0.728 68 283 P -2.575 8 35 |
Mw Moment 2.200e+16 N-m Magnitude 4.83 Depth 10.0 km Percent DC 99% Half Duration – Catalog NN (nn00495477) Data Source NN1 Contributor NN1 Nodal Planes Plane Strike Dip Rake NP1 82 83 -9 NP2 173 81 -173 Principal Axes Axis Value Plunge Azimuth T 2.213 2 128 N -0.016 78 226 P -2.186 11 37 |
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 -30 o DIST/3.3 +70 rtr taper w 0.1 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 1.0 85 90 0 4.47 0.4425 WVFGRD96 2.0 85 90 -5 4.57 0.5693 WVFGRD96 3.0 85 90 -5 4.62 0.6344 WVFGRD96 4.0 80 80 -15 4.67 0.6838 WVFGRD96 5.0 80 80 -15 4.71 0.7247 WVFGRD96 6.0 80 80 -15 4.73 0.7586 WVFGRD96 7.0 80 85 -15 4.76 0.7889 WVFGRD96 8.0 80 80 -20 4.80 0.8178 WVFGRD96 9.0 80 85 -20 4.81 0.8344 WVFGRD96 10.0 80 85 -15 4.83 0.8454 WVFGRD96 11.0 80 85 -15 4.84 0.8525 WVFGRD96 12.0 80 85 -15 4.85 0.8548 WVFGRD96 13.0 80 85 -15 4.86 0.8524 WVFGRD96 14.0 80 85 -10 4.87 0.8469 WVFGRD96 15.0 80 85 -10 4.88 0.8389 WVFGRD96 16.0 80 85 -10 4.89 0.8287 WVFGRD96 17.0 80 85 -10 4.89 0.8170 WVFGRD96 18.0 260 90 10 4.90 0.8002 WVFGRD96 19.0 80 85 -10 4.90 0.7894 WVFGRD96 20.0 265 90 10 4.91 0.7709 WVFGRD96 21.0 265 90 10 4.91 0.7574 WVFGRD96 22.0 85 85 -5 4.92 0.7465 WVFGRD96 23.0 85 85 -5 4.92 0.7323 WVFGRD96 24.0 85 85 -5 4.93 0.7178 WVFGRD96 25.0 85 85 -5 4.93 0.7037 WVFGRD96 26.0 265 90 5 4.94 0.6864 WVFGRD96 27.0 85 85 -5 4.94 0.6760 WVFGRD96 28.0 265 90 5 4.95 0.6591 WVFGRD96 29.0 85 85 -5 4.95 0.6488
The best solution is
WVFGRD96 12.0 80 85 -15 4.85 0.8548
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 -30 o DIST/3.3 +70 rtr taper w 0.1 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 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