The ANSS event ID is us20002pbp and the event page is at https://earthquake.usgs.gov/earthquakes/eventpage/us20002pbp/executive.
2015/06/11 23:31:38 36.283 -97.519 5.7 3.7 Oklhaoma
USGS/SLU Moment Tensor Solution ENS 2015/06/11 23:31:38:0 36.28 -97.52 5.7 3.7 Oklhaoma Stations used: GS.KAN08 GS.KAN12 GS.KAN14 GS.KAN16 GS.KAN17 GS.KS20 GS.KS21 GS.OK025 GS.OK029 GS.OK030 GS.OK031 GS.OK032 N4.R32B N4.T35B N4.U38B OK.BCOK OK.CROK OK.FNO OK.X37A US.CBKS US.KSU1 US.WMOK Filtering commands used: cut o DIST/3.3 -30 o DIST/3.3 +70 rtr taper w 0.1 hp c 0.03 n 3 lp c 0.07 n 3 Best Fitting Double Couple Mo = 3.76e+21 dyne-cm Mw = 3.65 Z = 4 km Plane Strike Dip Rake NP1 25 90 -175 NP2 295 85 0 Principal Axes: Axis Value Plunge Azimuth T 3.76e+21 4 160 N 0.00e+00 85 25 P -3.76e+21 4 250 Moment Tensor: (dyne-cm) Component Value Mxx 2.87e+21 Mxy -2.41e+21 Mxz -1.38e+20 Myy -2.87e+21 Myz 2.97e+20 Mzz 0.00e+00 ############## ###################--- #####################------- #####################--------- #######################----------- #######################------------- --#####################--------------- --------###############----------------- -------------#########------------------ ------------------####-------------------- ---------------------#-------------------- ---------------------#####---------------- --------------------##########------------ ---------------##############-------- P --------------##################----- -------------######################- -------------####################### -----------####################### ---------##################### -------##################### ---############# ### ############ T Global CMT Convention Moment Tensor: R T P 0.00e+00 -1.38e+20 -2.97e+20 -1.38e+20 2.87e+21 2.41e+21 -2.97e+20 2.41e+21 -2.87e+21 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20150611233138/index.html |
STK = 295 DIP = 85 RAKE = 0 MW = 3.65 HS = 4.0
The NDK file is 20150611233138.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 2015/06/11 23:31:38:0 36.28 -97.52 5.7 3.7 Oklhaoma Stations used: GS.KAN08 GS.KAN12 GS.KAN14 GS.KAN16 GS.KAN17 GS.KS20 GS.KS21 GS.OK025 GS.OK029 GS.OK030 GS.OK031 GS.OK032 N4.R32B N4.T35B N4.U38B OK.BCOK OK.CROK OK.FNO OK.X37A US.CBKS US.KSU1 US.WMOK Filtering commands used: cut o DIST/3.3 -30 o DIST/3.3 +70 rtr taper w 0.1 hp c 0.03 n 3 lp c 0.07 n 3 Best Fitting Double Couple Mo = 3.76e+21 dyne-cm Mw = 3.65 Z = 4 km Plane Strike Dip Rake NP1 25 90 -175 NP2 295 85 0 Principal Axes: Axis Value Plunge Azimuth T 3.76e+21 4 160 N 0.00e+00 85 25 P -3.76e+21 4 250 Moment Tensor: (dyne-cm) Component Value Mxx 2.87e+21 Mxy -2.41e+21 Mxz -1.38e+20 Myy -2.87e+21 Myz 2.97e+20 Mzz 0.00e+00 ############## ###################--- #####################------- #####################--------- #######################----------- #######################------------- --#####################--------------- --------###############----------------- -------------#########------------------ ------------------####-------------------- ---------------------#-------------------- ---------------------#####---------------- --------------------##########------------ ---------------##############-------- P --------------##################----- -------------######################- -------------####################### -----------####################### ---------##################### -------##################### ---############# ### ############ T Global CMT Convention Moment Tensor: R T P 0.00e+00 -1.38e+20 -2.97e+20 -1.38e+20 2.87e+21 2.41e+21 -2.97e+20 2.41e+21 -2.87e+21 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20150611233138/index.html |
Regional Moment Tensor (Mwr) Moment 4.471e+14 N-m Magnitude 3.70 Depth 5.0 km Percent DC 52% Half Duration – Catalog US (us20002pbp) Data Source US1 Contributor US1 Nodal Planes Plane Strike Dip Rake NP1 307 88 28 NP2 216 62 178 Principal Axes Axis Value Plunge Azimuth T 4.943 21 175 N -1.180 62 310 P -3.763 18 78 |
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: mLg computed using the IASPEI formula. Center: mLg residuals versus epicentral distance ; the values used for the trimmed mean magnitude estimate are indicated.
Right: residuals as a function of distance and azimuth.
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.
![]() |
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.
![]() |
|
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 0.03 n 3 lp c 0.07 n 3The results of this grid search are as follow:
DEPTH STK DIP RAKE MW FIT WVFGRD96 1.0 130 90 -25 3.44 0.4046 WVFGRD96 2.0 310 85 0 3.52 0.4625 WVFGRD96 3.0 115 90 -5 3.60 0.4916 WVFGRD96 4.0 295 85 0 3.65 0.4948 WVFGRD96 5.0 295 85 0 3.67 0.4784 WVFGRD96 6.0 115 90 -5 3.70 0.4533 WVFGRD96 7.0 120 80 10 3.70 0.4412 WVFGRD96 8.0 120 80 15 3.74 0.4339 WVFGRD96 9.0 120 80 15 3.75 0.4211 WVFGRD96 10.0 120 75 15 3.76 0.4109 WVFGRD96 11.0 120 75 15 3.77 0.4018 WVFGRD96 12.0 300 80 20 3.78 0.3904 WVFGRD96 13.0 310 75 20 3.77 0.3839 WVFGRD96 14.0 310 75 20 3.78 0.3788 WVFGRD96 15.0 310 75 20 3.78 0.3741 WVFGRD96 16.0 310 80 20 3.80 0.3703 WVFGRD96 17.0 310 80 20 3.80 0.3667 WVFGRD96 18.0 310 80 20 3.81 0.3635 WVFGRD96 19.0 310 80 20 3.82 0.3614 WVFGRD96 20.0 310 80 20 3.82 0.3595 WVFGRD96 21.0 310 80 20 3.83 0.3580 WVFGRD96 22.0 310 80 20 3.84 0.3573 WVFGRD96 23.0 310 80 20 3.85 0.3575 WVFGRD96 24.0 310 80 20 3.86 0.3582 WVFGRD96 25.0 310 80 20 3.86 0.3588 WVFGRD96 26.0 310 80 20 3.87 0.3593 WVFGRD96 27.0 300 80 20 3.88 0.3612 WVFGRD96 28.0 300 80 20 3.89 0.3632 WVFGRD96 29.0 300 80 20 3.90 0.3645
The best solution is
WVFGRD96 4.0 295 85 0 3.65 0.4948
The mechanism corresponding to the best fit is
![]() |
|
The best fit as a function of depth is given in the following figure:
![]() |
|
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 0.03 n 3 lp c 0.07 n 3
![]() |
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. |
![]() |
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