2011/05/09 23:28:54 37.139 -104.726 4.9 3.90 Colorado
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution ENS 2011/05/09 23:28:54:0 37.14 -104.73 4.9 3.9 Colorado Stations used: AR.X18A IU.ANMO IW.SMCO TA.KSCO TA.MSTX TA.O20A TA.O31A TA.Q32A TA.R32A TA.S22A TA.S32A TA.S33A TA.T25A TA.T32A TA.T33A TA.U32A TA.U33A TA.V32A TA.V33A TA.W18A TA.W32A US.AMTX US.CBKS US.ISCO US.MVCO US.SDCO US.WMOK UU.BRPU UU.CVRU UU.PNSU UU.SRU Filtering commands used: hp c 0.02 n 3 lp c 0.06 n 3 Best Fitting Double Couple Mo = 5.31e+21 dyne-cm Mw = 3.75 Z = 3 km Plane Strike Dip Rake NP1 2 50 -113 NP2 215 45 -65 Principal Axes: Axis Value Plunge Azimuth T 5.31e+21 3 108 N 0.00e+00 17 17 P -5.31e+21 72 206 Moment Tensor: (dyne-cm) Component Value Mxx 9.21e+19 Mxy -1.72e+21 Mxz 1.30e+21 Myy 4.72e+21 Myz 9.10e+20 Mzz -4.81e+21 #########----- ###############------- ################----######## ##############--------######## #############------------######### ############--------------########## ###########-----------------########## ###########------------------########### ##########--------------------########## ##########---------------------########### #########----------------------########### ########-----------------------########### ########--------- -----------########### ######---------- P -----------######## ######---------- ----------######### T #####-----------------------######### ####----------------------########## ###---------------------########## ##-------------------######### #------------------######### --------------######## --------###### Global CMT Convention Moment Tensor: R T P -4.81e+21 1.30e+21 -9.10e+20 1.30e+21 9.21e+19 1.72e+21 -9.10e+20 1.72e+21 4.72e+21 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20110509232854/index.html |
STK = 215 DIP = 45 RAKE = -65 MW = 3.75 HS = 3.0
The NDK file is 20110509232854.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution ENS 2011/05/09 23:28:54:0 37.14 -104.73 4.9 3.9 Colorado Stations used: AR.X18A IU.ANMO IW.SMCO TA.KSCO TA.MSTX TA.O20A TA.O31A TA.Q32A TA.R32A TA.S22A TA.S32A TA.S33A TA.T25A TA.T32A TA.T33A TA.U32A TA.U33A TA.V32A TA.V33A TA.W18A TA.W32A US.AMTX US.CBKS US.ISCO US.MVCO US.SDCO US.WMOK UU.BRPU UU.CVRU UU.PNSU UU.SRU Filtering commands used: hp c 0.02 n 3 lp c 0.06 n 3 Best Fitting Double Couple Mo = 5.31e+21 dyne-cm Mw = 3.75 Z = 3 km Plane Strike Dip Rake NP1 2 50 -113 NP2 215 45 -65 Principal Axes: Axis Value Plunge Azimuth T 5.31e+21 3 108 N 0.00e+00 17 17 P -5.31e+21 72 206 Moment Tensor: (dyne-cm) Component Value Mxx 9.21e+19 Mxy -1.72e+21 Mxz 1.30e+21 Myy 4.72e+21 Myz 9.10e+20 Mzz -4.81e+21 #########----- ###############------- ################----######## ##############--------######## #############------------######### ############--------------########## ###########-----------------########## ###########------------------########### ##########--------------------########## ##########---------------------########### #########----------------------########### ########-----------------------########### ########--------- -----------########### ######---------- P -----------######## ######---------- ----------######### T #####-----------------------######### ####----------------------########## ###---------------------########## ##-------------------######### #------------------######### --------------######## --------###### Global CMT Convention Moment Tensor: R T P -4.81e+21 1.30e+21 -9.10e+20 1.30e+21 9.21e+19 1.72e+21 -9.10e+20 1.72e+21 4.72e+21 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20110509232854/index.html |
(a) mLg computed using the IASPEI formula; (b) mLg residuals ; the values used for the trimmed mean are indicated.
(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:
hp c 0.02 n 3 lp c 0.06 n 3The results of this grid search from 0.5 to 19 km depth are as follow:
DEPTH STK DIP RAKE MW FIT WVFGRD96 0.5 225 50 -45 3.54 0.4199 WVFGRD96 1.0 220 45 -50 3.60 0.4656 WVFGRD96 2.0 220 45 -55 3.68 0.5492 WVFGRD96 3.0 215 45 -65 3.75 0.5849 WVFGRD96 4.0 230 55 -45 3.76 0.5220 WVFGRD96 5.0 240 65 -25 3.75 0.4568 WVFGRD96 6.0 240 70 -15 3.76 0.4207 WVFGRD96 7.0 245 80 15 3.79 0.4025 WVFGRD96 8.0 245 75 15 3.82 0.3997 WVFGRD96 9.0 245 75 20 3.84 0.3958 WVFGRD96 10.0 245 75 20 3.85 0.3919 WVFGRD96 11.0 85 60 35 3.79 0.3920 WVFGRD96 12.0 85 60 35 3.80 0.4049 WVFGRD96 13.0 85 65 40 3.82 0.4155 WVFGRD96 14.0 90 60 40 3.83 0.4253 WVFGRD96 15.0 90 60 40 3.83 0.4335 WVFGRD96 16.0 240 80 -40 3.84 0.4413 WVFGRD96 17.0 240 80 -40 3.85 0.4506 WVFGRD96 18.0 240 85 -35 3.85 0.4595 WVFGRD96 19.0 240 85 -35 3.86 0.4675 WVFGRD96 20.0 240 85 -35 3.87 0.4742 WVFGRD96 21.0 65 90 35 3.89 0.4773 WVFGRD96 22.0 65 90 35 3.90 0.4807 WVFGRD96 23.0 60 90 35 3.89 0.4839 WVFGRD96 24.0 60 90 35 3.90 0.4868 WVFGRD96 25.0 60 90 35 3.92 0.4893 WVFGRD96 26.0 60 90 35 3.93 0.4902 WVFGRD96 27.0 60 90 35 3.93 0.4900 WVFGRD96 28.0 60 90 35 3.94 0.4889 WVFGRD96 29.0 60 90 35 3.95 0.4859
The best solution is
WVFGRD96 3.0 215 45 -65 3.75 0.5849
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
hp c 0.02 n 3 lp c 0.06 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: