USGS/SLU Moment Tensor Solution ENS 2018/02/28 01:27:47:0 62.35 148.72 27.8 4.1 Alaska Stations used: AK.CAST AK.DHY AK.GHO AK.KLU AK.KNK AK.KTH AK.MLY AK.NEA2 AK.RC01 AK.RND AK.SAW AK.SCM AK.SSN AK.TRF AT.PMR TA.M22K TA.M24K TA.POKR Filtering commands used: cut o DIST/3.3 30 o DIST/3.3 +40 rtr taper w 0.1 hp c 0.03 n 3 lp c 0.08 n 3 Best Fitting Double Couple Mo = 3.43e+22 dynecm Mw = 4.29 Z = 52 km Plane Strike Dip Rake NP1 290 55 55 NP2 59 48 129 Principal Axes: Axis Value Plunge Azimuth T 3.43e+22 4 356 N 0.00e+00 28 88 P 3.43e+22 62 259 Moment Tensor: (dynecm) Component Value Mxx 3.37e+22 Mxy 3.86e+21 Mxz 5.17e+21 Myy 7.27e+21 Myz 1.39e+22 Mzz 2.64e+22 #### T ####### ######## ########### ############################ ############################## ################################## ############################## ################# ########## ####### ###    P ##  ##### ######## ########## ############ ############### #################### ############################## ############################ ###################### ############## Global CMT Convention Moment Tensor: R T P 2.64e+22 5.17e+21 1.39e+22 5.17e+21 3.37e+22 3.86e+21 1.39e+22 3.86e+21 7.27e+21 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20180228012747/index.html 
STK = 290 DIP = 55 RAKE = 55 MW = 4.29 HS = 52.0
The NDK file is 20180228012747.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution ENS 2018/02/28 01:27:47:0 62.35 148.72 27.8 4.1 Alaska Stations used: AK.CAST AK.DHY AK.GHO AK.KLU AK.KNK AK.KTH AK.MLY AK.NEA2 AK.RC01 AK.RND AK.SAW AK.SCM AK.SSN AK.TRF AT.PMR TA.M22K TA.M24K TA.POKR Filtering commands used: cut o DIST/3.3 30 o DIST/3.3 +40 rtr taper w 0.1 hp c 0.03 n 3 lp c 0.08 n 3 Best Fitting Double Couple Mo = 3.43e+22 dynecm Mw = 4.29 Z = 52 km Plane Strike Dip Rake NP1 290 55 55 NP2 59 48 129 Principal Axes: Axis Value Plunge Azimuth T 3.43e+22 4 356 N 0.00e+00 28 88 P 3.43e+22 62 259 Moment Tensor: (dynecm) Component Value Mxx 3.37e+22 Mxy 3.86e+21 Mxz 5.17e+21 Myy 7.27e+21 Myz 1.39e+22 Mzz 2.64e+22 #### T ####### ######## ########### ############################ ############################## ################################## ############################## ################# ########## ####### ###    P ##  ##### ######## ########## ############ ############### #################### ############################## ############################ ###################### ############## Global CMT Convention Moment Tensor: R T P 2.64e+22 5.17e+21 1.39e+22 5.17e+21 3.37e+22 3.86e+21 1.39e+22 3.86e+21 7.27e+21 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20180228012747/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.

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 30 o DIST/3.3 +40 rtr taper w 0.1 hp c 0.03 n 3 lp c 0.08 n 3The results of this grid search from 0.5 to 19 km depth are as follow:
DEPTH STK DIP RAKE MW FIT WVFGRD96 2.0 65 50 55 3.55 0.2865 WVFGRD96 4.0 240 70 50 3.64 0.3186 WVFGRD96 6.0 35 55 40 3.69 0.3523 WVFGRD96 8.0 30 50 45 3.77 0.3676 WVFGRD96 10.0 35 60 40 3.78 0.3712 WVFGRD96 12.0 335 50 50 3.84 0.3874 WVFGRD96 14.0 330 55 45 3.85 0.3980 WVFGRD96 16.0 330 55 45 3.88 0.4036 WVFGRD96 18.0 145 60 35 3.88 0.4145 WVFGRD96 20.0 145 60 35 3.91 0.4278 WVFGRD96 22.0 145 60 35 3.93 0.4389 WVFGRD96 24.0 140 70 30 3.94 0.4497 WVFGRD96 26.0 140 70 25 3.96 0.4621 WVFGRD96 28.0 140 75 25 3.98 0.4728 WVFGRD96 30.0 310 60 15 4.01 0.5008 WVFGRD96 32.0 310 60 20 4.03 0.5275 WVFGRD96 34.0 305 60 25 4.05 0.5531 WVFGRD96 36.0 305 60 25 4.07 0.5775 WVFGRD96 38.0 300 60 30 4.10 0.5999 WVFGRD96 40.0 295 50 40 4.18 0.6234 WVFGRD96 42.0 295 50 45 4.21 0.6363 WVFGRD96 44.0 295 55 45 4.22 0.6472 WVFGRD96 46.0 295 55 45 4.24 0.6604 WVFGRD96 48.0 290 55 50 4.26 0.6699 WVFGRD96 50.0 290 55 55 4.28 0.6771 WVFGRD96 52.0 290 55 55 4.29 0.6810 WVFGRD96 54.0 290 55 55 4.29 0.6807 WVFGRD96 56.0 290 55 55 4.30 0.6763 WVFGRD96 58.0 295 60 45 4.30 0.6712 WVFGRD96 60.0 295 60 45 4.30 0.6643 WVFGRD96 62.0 290 60 50 4.31 0.6566 WVFGRD96 64.0 290 60 50 4.31 0.6486 WVFGRD96 66.0 295 65 45 4.31 0.6392 WVFGRD96 68.0 295 65 45 4.31 0.6320 WVFGRD96 70.0 295 65 40 4.31 0.6260 WVFGRD96 72.0 295 65 40 4.31 0.6194 WVFGRD96 74.0 295 65 40 4.31 0.6124 WVFGRD96 76.0 295 70 40 4.32 0.6079 WVFGRD96 78.0 295 70 40 4.32 0.6031 WVFGRD96 80.0 295 70 40 4.32 0.5977 WVFGRD96 82.0 295 70 40 4.32 0.5916 WVFGRD96 84.0 295 70 40 4.32 0.5857 WVFGRD96 86.0 295 70 40 4.32 0.5796 WVFGRD96 88.0 295 70 40 4.32 0.5735 WVFGRD96 90.0 295 75 40 4.33 0.5678 WVFGRD96 92.0 295 75 40 4.33 0.5632 WVFGRD96 94.0 295 75 40 4.34 0.5580 WVFGRD96 96.0 295 75 40 4.34 0.5530 WVFGRD96 98.0 300 75 30 4.33 0.5488
The best solution is
WVFGRD96 52.0 290 55 55 4.29 0.6810
The mechanism correspond 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 observedpredicted 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 30 o DIST/3.3 +40 rtr taper w 0.1 hp c 0.03 n 3 lp c 0.08 n 3

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 1D 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 0.302E02 0.679E02 0.00 0.00 1.00 1.00 6.1000 5.5445 3.2953 2.6089 0.349E02 0.784E02 0.00 0.00 1.00 1.00 13.0000 6.2708 3.7396 2.7812 0.212E02 0.476E02 0.00 0.00 1.00 1.00 19.0000 6.4075 3.7680 2.8223 0.111E02 0.249E02 0.00 0.00 1.00 1.00 0.0000 7.9000 4.6200 3.2760 0.164E10 0.370E10 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: