2013/06/27 02:45:35 47.824 -120.689 9.1 4.1 Washington
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution ENS 2013/06/27 02:45:35:0 47.82 -120.69 9.1 4.1 Washington Stations used: US.HAWA US.NLWA UW.BRAN UW.DAVN UW.DDRF UW.LON UW.LTY UW.MRBL UW.PHIN UW.STOR UW.TUCA UW.UMAT UW.WOLL Filtering commands used: cut a -30 a 120 rtr taper w 0.1 hp c 0.02 n 3 lp c 0.07 n 3 Best Fitting Double Couple Mo = 5.31e+21 dyne-cm Mw = 3.75 Z = 12 km Plane Strike Dip Rake NP1 306 64 134 NP2 60 50 35 Principal Axes: Axis Value Plunge Azimuth T 5.31e+21 50 266 N 0.00e+00 39 103 P -5.31e+21 8 6 Moment Tensor: (dyne-cm) Component Value Mxx -5.13e+21 Mxy -3.67e+20 Mxz -9.40e+20 Myy 2.14e+21 Myz -2.69e+21 Mzz 3.00e+21 ------- P ---- ----------- -------- ---------------------------- ------------------------------ ######---------------------------- #############----------------------- ##################-------------------# ######################---------------### #########################------------### ############################---------##### ######### ##################------###### ######### T ####################---####### ######### ############################## ###############################---###### ############################-------##### #########################----------### ####################--------------## ---###########-------------------- ------------------------------ ---------------------------- ---------------------- -------------- Global CMT Convention Moment Tensor: R T P 3.00e+21 -9.40e+20 2.69e+21 -9.40e+20 -5.13e+21 3.67e+20 2.69e+21 3.67e+20 2.14e+21 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20130627024535/index.html |
STK = 60 DIP = 50 RAKE = 35 MW = 3.75 HS = 12.0
The NDK file is 20130627024535.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution ENS 2013/06/27 02:45:35:0 47.82 -120.69 9.1 4.1 Washington Stations used: US.HAWA US.NLWA UW.BRAN UW.DAVN UW.DDRF UW.LON UW.LTY UW.MRBL UW.PHIN UW.STOR UW.TUCA UW.UMAT UW.WOLL Filtering commands used: cut a -30 a 120 rtr taper w 0.1 hp c 0.02 n 3 lp c 0.07 n 3 Best Fitting Double Couple Mo = 5.31e+21 dyne-cm Mw = 3.75 Z = 12 km Plane Strike Dip Rake NP1 306 64 134 NP2 60 50 35 Principal Axes: Axis Value Plunge Azimuth T 5.31e+21 50 266 N 0.00e+00 39 103 P -5.31e+21 8 6 Moment Tensor: (dyne-cm) Component Value Mxx -5.13e+21 Mxy -3.67e+20 Mxz -9.40e+20 Myy 2.14e+21 Myz -2.69e+21 Mzz 3.00e+21 ------- P ---- ----------- -------- ---------------------------- ------------------------------ ######---------------------------- #############----------------------- ##################-------------------# ######################---------------### #########################------------### ############################---------##### ######### ##################------###### ######### T ####################---####### ######### ############################## ###############################---###### ############################-------##### #########################----------### ####################--------------## ---###########-------------------- ------------------------------ ---------------------------- ---------------------- -------------- Global CMT Convention Moment Tensor: R T P 3.00e+21 -9.40e+20 2.69e+21 -9.40e+20 -5.13e+21 3.67e+20 2.69e+21 3.67e+20 2.14e+21 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20130627024535/index.html |
us usb000i15x-neic-mwr Type Mwr Moment 5.63e+14 N-m Magnitude 3.8 Percent DC 39% Depth 14.0 km Author neic Updated 2013-06-27 03:57:11 UTC Principal Axes Axis Value Plunge Azimuth T 4.764 32 291 N 1.450 47 64 P -6.214 25 184 Nodal Planes Plane Strike Dip Rake NP1 59° 86 42 NP2 325° 48 174 |
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(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 a -30 a 120 rtr taper w 0.1 hp c 0.02 n 3 lp c 0.07 n 3The results of this grid search from 0.5 to 19 km depth are as follow:
DEPTH STK DIP RAKE MW FIT WVFGRD96 0.5 285 45 85 3.41 0.3003 WVFGRD96 1.0 275 65 35 3.49 0.2779 WVFGRD96 2.0 255 70 25 3.51 0.3270 WVFGRD96 3.0 25 65 -45 3.57 0.3456 WVFGRD96 4.0 60 80 -45 3.59 0.3770 WVFGRD96 5.0 70 40 25 3.63 0.4182 WVFGRD96 6.0 70 45 30 3.65 0.4631 WVFGRD96 7.0 70 45 35 3.67 0.5013 WVFGRD96 8.0 75 40 45 3.74 0.5289 WVFGRD96 9.0 70 45 45 3.74 0.5561 WVFGRD96 10.0 70 45 45 3.75 0.5708 WVFGRD96 11.0 65 50 35 3.75 0.5775 WVFGRD96 12.0 60 50 35 3.75 0.5792 WVFGRD96 13.0 60 50 30 3.76 0.5761 WVFGRD96 14.0 55 55 25 3.76 0.5700 WVFGRD96 15.0 55 55 25 3.77 0.5637 WVFGRD96 16.0 55 55 25 3.77 0.5547 WVFGRD96 17.0 50 55 20 3.78 0.5446 WVFGRD96 18.0 50 55 20 3.79 0.5332 WVFGRD96 19.0 50 55 20 3.79 0.5220 WVFGRD96 20.0 50 55 15 3.80 0.5097 WVFGRD96 21.0 50 55 15 3.81 0.4979 WVFGRD96 22.0 50 55 15 3.81 0.4845 WVFGRD96 23.0 50 55 15 3.81 0.4706 WVFGRD96 24.0 50 55 10 3.82 0.4575 WVFGRD96 25.0 50 55 10 3.82 0.4445 WVFGRD96 26.0 50 55 10 3.83 0.4329 WVFGRD96 27.0 50 55 10 3.83 0.4232 WVFGRD96 28.0 50 55 10 3.84 0.4122 WVFGRD96 29.0 50 50 -15 3.85 0.4029
The best solution is
WVFGRD96 12.0 60 50 35 3.75 0.5792
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 a -30 a 120 rtr taper w 0.1 hp c 0.02 n 3 lp c 0.07 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: