The ANSS event ID is nn00434307 and the event page is at https://earthquake.usgs.gov/earthquakes/eventpage/nn00434307/executive.
2014/01/14 06:10:22 38.570 -118.445 8.7 3.8 Nevada
USGS/SLU Moment Tensor Solution ENS 2014/01/14 06:10:22:0 38.57 -118.44 8.7 3.8 Nevada Stations used: AE.W13A AZ.RDM BK.CMB CI.ADO CI.ARV CI.CWC CI.DEC CI.DGR CI.EDW2 CI.FUR CI.GRA CI.GSC CI.HEC CI.LRL CI.MLAC CI.MPM CI.MUR CI.NEE2 CI.PASC CI.RPV CI.SHO CI.SLA CI.VTV IM.NV31 LB.DAC NN.BEK NN.KVN NN.OMMB NN.PAH NN.PNT NN.PRN NN.RUB NN.UNVG NN.VCN NN.WAK NN.YER TA.K04D TA.M04C TA.R11A US.DUG US.ELK US.TPNV UU.CCUT UU.KNB UU.LCMT UU.PKCU UU.PSUT UU.SZCU UU.TCRU UU.VRUT UU.ZNPU Filtering commands used: cut a -30 a 180 rtr taper w 0.1 hp c 0.02 n 3 lp c 0.10 n 3 br c 0.12 0.25 n 4 p 2 Best Fitting Double Couple Mo = 3.51e+21 dyne-cm Mw = 3.63 Z = 8 km Plane Strike Dip Rake NP1 172 86 150 NP2 265 60 5 Principal Axes: Axis Value Plunge Azimuth T 3.51e+21 24 125 N 0.00e+00 60 345 P -3.51e+21 17 223 Moment Tensor: (dyne-cm) Component Value Mxx -7.88e+20 Mxy -2.96e+21 Mxz -5.23e+13 Myy 5.23e+20 Myz 1.75e+21 Mzz 2.65e+20 ####---------- ########-------------- ###########----------------- ############------------------ ###############------------------- ################-------------------- #################--------------------- #############-----##############-------- ########----------###################--- #####---------------#####################- ###-----------------###################### #-------------------###################### --------------------###################### --------------------#################### --------------------############ ##### -------------------############ T #### ---- -----------############ ### --- P ------------################ - ------------############## ----------------############ -------------######### ---------##### Global CMT Convention Moment Tensor: R T P 2.65e+20 -5.23e+13 -1.75e+21 -5.23e+13 -7.88e+20 2.96e+21 -1.75e+21 2.96e+21 5.23e+20 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20140114061022/index.html |
STK = 265 DIP = 60 RAKE = 5 MW = 3.63 HS = 8.0
The NDK file is 20140114061022.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 2014/01/14 06:10:22:0 38.57 -118.44 8.7 3.8 Nevada Stations used: AE.W13A AZ.RDM BK.CMB CI.ADO CI.ARV CI.CWC CI.DEC CI.DGR CI.EDW2 CI.FUR CI.GRA CI.GSC CI.HEC CI.LRL CI.MLAC CI.MPM CI.MUR CI.NEE2 CI.PASC CI.RPV CI.SHO CI.SLA CI.VTV IM.NV31 LB.DAC NN.BEK NN.KVN NN.OMMB NN.PAH NN.PNT NN.PRN NN.RUB NN.UNVG NN.VCN NN.WAK NN.YER TA.K04D TA.M04C TA.R11A US.DUG US.ELK US.TPNV UU.CCUT UU.KNB UU.LCMT UU.PKCU UU.PSUT UU.SZCU UU.TCRU UU.VRUT UU.ZNPU Filtering commands used: cut a -30 a 180 rtr taper w 0.1 hp c 0.02 n 3 lp c 0.10 n 3 br c 0.12 0.25 n 4 p 2 Best Fitting Double Couple Mo = 3.51e+21 dyne-cm Mw = 3.63 Z = 8 km Plane Strike Dip Rake NP1 172 86 150 NP2 265 60 5 Principal Axes: Axis Value Plunge Azimuth T 3.51e+21 24 125 N 0.00e+00 60 345 P -3.51e+21 17 223 Moment Tensor: (dyne-cm) Component Value Mxx -7.88e+20 Mxy -2.96e+21 Mxz -5.23e+13 Myy 5.23e+20 Myz 1.75e+21 Mzz 2.65e+20 ####---------- ########-------------- ###########----------------- ############------------------ ###############------------------- ################-------------------- #################--------------------- #############-----##############-------- ########----------###################--- #####---------------#####################- ###-----------------###################### #-------------------###################### --------------------###################### --------------------#################### --------------------############ ##### -------------------############ T #### ---- -----------############ ### --- P ------------################ - ------------############## ----------------############ -------------######### ---------##### Global CMT Convention Moment Tensor: R T P 2.65e+20 -5.23e+13 -1.75e+21 -5.23e+13 -7.88e+20 2.96e+21 -1.75e+21 2.96e+21 5.23e+20 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20140114061022/index.html |
Moment 3.12e+14 N-m Magnitude 3.6 Percent DC 99% Depth 8.0 km Updated 2014-01-14 06:36:46 UTC Author nn Catalog nn Contributor nn Code nn00434307-nn-mt Principal Axes Axis Value Plunge Azimuth T 3.124 20 121 N -0.015 57 357 P -3.109 25 221 Nodal Planes Plane Strike Dip Rake NP1 352 87 -147 NP2 260 58 -4 |
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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 a -30 a 180 rtr taper w 0.1 hp c 0.02 n 3 lp c 0.10 n 3 br c 0.12 0.25 n 4 p 2The results of this grid search are as follow:
DEPTH STK DIP RAKE MW FIT WVFGRD96 0.5 255 75 -15 3.23 0.2918 WVFGRD96 1.0 80 90 -5 3.27 0.3283 WVFGRD96 2.0 260 90 5 3.42 0.4690 WVFGRD96 3.0 260 80 0 3.48 0.5110 WVFGRD96 4.0 265 70 5 3.52 0.5290 WVFGRD96 5.0 265 65 5 3.56 0.5454 WVFGRD96 6.0 265 60 5 3.58 0.5580 WVFGRD96 7.0 265 65 5 3.59 0.5640 WVFGRD96 8.0 265 60 5 3.63 0.5673 WVFGRD96 9.0 265 60 5 3.64 0.5626 WVFGRD96 10.0 265 60 5 3.65 0.5556 WVFGRD96 11.0 265 65 5 3.65 0.5478 WVFGRD96 12.0 265 65 5 3.66 0.5404 WVFGRD96 13.0 265 65 5 3.67 0.5321 WVFGRD96 14.0 265 65 5 3.68 0.5233 WVFGRD96 15.0 265 70 5 3.69 0.5146 WVFGRD96 16.0 265 70 5 3.69 0.5062 WVFGRD96 17.0 265 70 5 3.70 0.4971 WVFGRD96 18.0 90 70 20 3.72 0.4879 WVFGRD96 19.0 90 70 20 3.73 0.4825 WVFGRD96 20.0 90 70 20 3.74 0.4770 WVFGRD96 21.0 90 75 25 3.75 0.4717 WVFGRD96 22.0 90 75 25 3.76 0.4656 WVFGRD96 23.0 90 75 25 3.77 0.4594 WVFGRD96 24.0 90 75 25 3.77 0.4529 WVFGRD96 25.0 90 75 25 3.78 0.4464 WVFGRD96 26.0 90 75 25 3.79 0.4401 WVFGRD96 27.0 90 75 25 3.80 0.4334 WVFGRD96 28.0 90 75 25 3.80 0.4270 WVFGRD96 29.0 90 75 25 3.81 0.4205
The best solution is
WVFGRD96 8.0 265 60 5 3.63 0.5673
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 a -30 a 180 rtr taper w 0.1 hp c 0.02 n 3 lp c 0.10 n 3 br c 0.12 0.25 n 4 p 2
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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