USGS/SLU Moment Tensor Solution ENS 2017/09/09 11:52:49:0 42.56 -111.40 1.6 3.7 Idaho Stations used: GS.ID05 GS.ID06 GS.ID07 GS.ID08 IW.FXWY IW.IMW IW.MFID IW.MOOW IW.REDW TA.H17A US.AHID US.BOZ US.BW06 US.DUG US.ELK US.HLID US.HWUT US.RLMT UU.BGU UU.CTU UU.HVU UU.MPU UU.NLU UU.RDMU UU.SPU UU.SRU UU.SWUT UU.TCU UU.TMU WY.YNR Filtering commands used: cut o DIST/3.3 -20 o DIST/3.3 +50 rtr taper w 0.1 hp c 0.03 n 3 lp c 0.10 n 3 Best Fitting Double Couple Mo = 1.06e+22 dyne-cm Mw = 3.95 Z = 9 km Plane Strike Dip Rake NP1 350 55 -120 NP2 215 45 -55 Principal Axes: Axis Value Plunge Azimuth T 1.06e+22 5 101 N 0.00e+00 24 9 P -1.06e+22 65 202 Moment Tensor: (dyne-cm) Component Value Mxx -1.18e+21 Mxy -2.61e+21 Mxz 3.52e+21 Myy 9.86e+21 Myz 2.46e+21 Mzz -8.68e+21 #####--------- ############---------- ############################ ##############-----########### #############---------############ ############------------############ ###########---------------############ ###########-----------------############ ##########------------------############ ##########--------------------############ #########---------------------############ ########----------------------######### ########----------------------######### T ######---------- ----------######### ######---------- P ----------########### #####---------- ----------########## ####-----------------------######### ###----------------------######### ##---------------------####### #--------------------####### -----------------##### -----------### Global CMT Convention Moment Tensor: R T P -8.68e+21 3.52e+21 -2.46e+21 3.52e+21 -1.18e+21 2.61e+21 -2.46e+21 2.61e+21 9.86e+21 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20170909115249/index.html |
STK = 215 DIP = 45 RAKE = -55 MW = 3.95 HS = 9.0
The NDK file is 20170909115249.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution ENS 2017/09/09 11:52:49:0 42.56 -111.40 1.6 3.7 Idaho Stations used: GS.ID05 GS.ID06 GS.ID07 GS.ID08 IW.FXWY IW.IMW IW.MFID IW.MOOW IW.REDW TA.H17A US.AHID US.BOZ US.BW06 US.DUG US.ELK US.HLID US.HWUT US.RLMT UU.BGU UU.CTU UU.HVU UU.MPU UU.NLU UU.RDMU UU.SPU UU.SRU UU.SWUT UU.TCU UU.TMU WY.YNR Filtering commands used: cut o DIST/3.3 -20 o DIST/3.3 +50 rtr taper w 0.1 hp c 0.03 n 3 lp c 0.10 n 3 Best Fitting Double Couple Mo = 1.06e+22 dyne-cm Mw = 3.95 Z = 9 km Plane Strike Dip Rake NP1 350 55 -120 NP2 215 45 -55 Principal Axes: Axis Value Plunge Azimuth T 1.06e+22 5 101 N 0.00e+00 24 9 P -1.06e+22 65 202 Moment Tensor: (dyne-cm) Component Value Mxx -1.18e+21 Mxy -2.61e+21 Mxz 3.52e+21 Myy 9.86e+21 Myz 2.46e+21 Mzz -8.68e+21 #####--------- ############---------- ############################ ##############-----########### #############---------############ ############------------############ ###########---------------############ ###########-----------------############ ##########------------------############ ##########--------------------############ #########---------------------############ ########----------------------######### ########----------------------######### T ######---------- ----------######### ######---------- P ----------########### #####---------- ----------########## ####-----------------------######### ###----------------------######### ##---------------------####### #--------------------####### -----------------##### -----------### Global CMT Convention Moment Tensor: R T P -8.68e+21 3.52e+21 -2.46e+21 3.52e+21 -1.18e+21 2.61e+21 -2.46e+21 2.61e+21 9.86e+21 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20170909115249/index.html |
(a) ML computed using the IASPEI formula for Horizontal components; (b) 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.
(a) ML computed using the IASPEI formula for Vertical components (research); (b) 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.
The focal mechanism was determined using broadband seismic waveforms. The location of the event and the and stations used for 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 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 -20 o DIST/3.3 +50 rtr taper w 0.1 hp c 0.03 n 3 lp c 0.10 n 3The results of this grid search from 0.5 to 19 km depth are as follow:
DEPTH STK DIP RAKE MW FIT WVFGRD96 1.0 70 65 40 3.53 0.3639 WVFGRD96 2.0 65 75 50 3.69 0.4399 WVFGRD96 3.0 235 85 -55 3.76 0.5294 WVFGRD96 4.0 230 75 -50 3.77 0.5938 WVFGRD96 5.0 220 60 -50 3.80 0.6430 WVFGRD96 6.0 215 50 -50 3.83 0.6889 WVFGRD96 7.0 220 50 -45 3.85 0.7124 WVFGRD96 8.0 215 45 -55 3.94 0.7353 WVFGRD96 9.0 215 45 -55 3.95 0.7433 WVFGRD96 10.0 215 45 -55 3.96 0.7411 WVFGRD96 11.0 215 45 -55 3.97 0.7339 WVFGRD96 12.0 215 45 -55 3.98 0.7213 WVFGRD96 13.0 215 45 -55 3.99 0.7099 WVFGRD96 14.0 215 45 -55 4.00 0.6947 WVFGRD96 15.0 215 45 -55 4.01 0.6776 WVFGRD96 16.0 215 45 -55 4.02 0.6610 WVFGRD96 17.0 215 45 -55 4.03 0.6435 WVFGRD96 18.0 215 45 -55 4.04 0.6242 WVFGRD96 19.0 215 45 -55 4.05 0.6061 WVFGRD96 20.0 220 45 -50 4.06 0.5873 WVFGRD96 21.0 220 45 -50 4.08 0.5714 WVFGRD96 22.0 220 45 -50 4.09 0.5550 WVFGRD96 23.0 220 45 -50 4.09 0.5389 WVFGRD96 24.0 220 45 -50 4.10 0.5226 WVFGRD96 25.0 220 45 -50 4.11 0.5062 WVFGRD96 26.0 215 45 -60 4.11 0.4906 WVFGRD96 27.0 215 45 -60 4.12 0.4781 WVFGRD96 28.0 215 45 -60 4.13 0.4663 WVFGRD96 29.0 215 45 -60 4.13 0.4549
The best solution is
WVFGRD96 9.0 215 45 -55 3.95 0.7433
The mechanism correspond 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 and because the velocity model used in the predictions may not be perfect. 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 -20 o DIST/3.3 +50 rtr taper w 0.1 hp c 0.03 n 3 lp c 0.10 n 3
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Focal mechanism sensitivity at the preferred depth. The red color indicates a very good fit to thewavefroms. 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.
Thanks also to the many seismic network operators whose dedication make this effort possible: University of Nevada Reno, University of Alaska, University of Washington, Oregon State University, University of Utah, Montana Bureas of Mines, UC Berkely, Caltech, UC San Diego, Saint Louis University, University of Memphis, Lamont Doherty Earth Observatory, the Iris stations and the Transportable Array of EarthScope.
The WUS.model used for the waveform synthetic seismograms and for the surface wave eigenfunctions and dispersion is as follows:
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
Here we tabulate the reasons for not using certain digital data sets
The following stations did not have a valid response files: