2016/02/15 10:41:45 60.904 -150.055 25.7 4.2 Alaska
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution ENS 2016/02/15 10:41:45:0 60.90 -150.05 25.7 4.2 Alaska Stations used: AK.BRLK AK.CAPN AK.CAST AK.CUT AK.FID AK.FIRE AK.GLI AK.HOM AK.KNK AK.KTH AK.PWL AK.RC01 AK.SAW AK.SCM AT.PMR AV.ILSW TA.J20K TA.M22K TA.M27K TA.N19K TA.N25K TA.O19K TA.O22K Filtering commands used: cut o DIST/3.3 -40 o DIST/3.3 +60 rtr taper w 0.1 hp c 0.03 n 3 lp c 0.07 n 3 Best Fitting Double Couple Mo = 2.69e+22 dyne-cm Mw = 4.22 Z = 46 km Plane Strike Dip Rake NP1 240 80 -30 NP2 336 61 -168 Principal Axes: Axis Value Plunge Azimuth T 2.69e+22 13 291 N 0.00e+00 59 43 P -2.69e+22 28 194 Moment Tensor: (dyne-cm) Component Value Mxx -1.64e+22 Mxy -1.35e+22 Mxz 1.30e+22 Myy 2.10e+22 Myz -2.82e+21 Mzz -4.60e+21 -------------- ######---------------- ###########----------------- ##############---------------- ##################---------------- #####################--------------# ####################-------######## # T #####################--############# # ###################---############## #####################-------############## ##################-----------############# ###############--------------############# ############------------------############ ########---------------------########### ######------------------------########## ###--------------------------######### ----------------------------######## ------------ ------------####### ---------- P ------------##### --------- ------------#### --------------------## -------------- Global CMT Convention Moment Tensor: R T P -4.60e+21 1.30e+22 2.82e+21 1.30e+22 -1.64e+22 1.35e+22 2.82e+21 1.35e+22 2.10e+22 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20160215104145/index.html |
STK = 240 DIP = 80 RAKE = -30 MW = 4.22 HS = 46.0
The NDK file is 20160215104145.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution ENS 2016/02/15 10:41:45:0 60.90 -150.05 25.7 4.2 Alaska Stations used: AK.BRLK AK.CAPN AK.CAST AK.CUT AK.FID AK.FIRE AK.GLI AK.HOM AK.KNK AK.KTH AK.PWL AK.RC01 AK.SAW AK.SCM AT.PMR AV.ILSW TA.J20K TA.M22K TA.M27K TA.N19K TA.N25K TA.O19K TA.O22K Filtering commands used: cut o DIST/3.3 -40 o DIST/3.3 +60 rtr taper w 0.1 hp c 0.03 n 3 lp c 0.07 n 3 Best Fitting Double Couple Mo = 2.69e+22 dyne-cm Mw = 4.22 Z = 46 km Plane Strike Dip Rake NP1 240 80 -30 NP2 336 61 -168 Principal Axes: Axis Value Plunge Azimuth T 2.69e+22 13 291 N 0.00e+00 59 43 P -2.69e+22 28 194 Moment Tensor: (dyne-cm) Component Value Mxx -1.64e+22 Mxy -1.35e+22 Mxz 1.30e+22 Myy 2.10e+22 Myz -2.82e+21 Mzz -4.60e+21 -------------- ######---------------- ###########----------------- ##############---------------- ##################---------------- #####################--------------# ####################-------######## # T #####################--############# # ###################---############## #####################-------############## ##################-----------############# ###############--------------############# ############------------------############ ########---------------------########### ######------------------------########## ###--------------------------######### ----------------------------######## ------------ ------------####### ---------- P ------------##### --------- ------------#### --------------------## -------------- Global CMT Convention Moment Tensor: R T P -4.60e+21 1.30e+22 2.82e+21 1.30e+22 -1.64e+22 1.35e+22 2.82e+21 1.35e+22 2.10e+22 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20160215104145/index.html USGS/SLU Moment Tensor Solution ENS 2016/02/15 10:41:46:0 60.84 -149.93 57.0 4.2 Alaska Stations used: AK.BRLK AK.CAPN AK.CAST AK.CUT AK.FID AK.FIRE AK.GLI AK.HOM AK.KNK AK.KTH AK.PWL AK.RC01 AK.SAW AK.SCM AT.PMR AV.ILSW TA.J20K TA.M22K TA.M27K TA.N19K TA.N25K TA.O19K TA.O22K Filtering commands used: cut o DIST/3.3 -40 o DIST/3.3 +60 rtr taper w 0.1 hp c 0.03 n 3 lp c 0.07 n 3 Best Fitting Double Couple Mo = 2.69e+22 dyne-cm Mw = 4.22 Z = 46 km Plane Strike Dip Rake NP1 235 85 -30 NP2 328 60 -174 Principal Axes: Axis Value Plunge Azimuth T 2.69e+22 17 285 N 0.00e+00 60 46 P -2.69e+22 24 187 Moment Tensor: (dyne-cm) Component Value Mxx -2.03e+22 Mxy -9.04e+21 Mxz 1.20e+22 Myy 2.26e+22 Myz -5.94e+21 Mzz -2.34e+21 -------------- ---------------------- ########-------------------- ############------------------ #################----------------- ####################------------#### ######################-------######### ## ####################--############# ## T ####################-############## ### #################-----############## ####################---------############# #################-------------############ ###############----------------########### ############------------------########## #########----------------------######### ######------------------------######## ###---------------------------###### -----------------------------##### ----------- -------------### ---------- P ------------### ------- ------------ -------------- Global CMT Convention Moment Tensor: R T P -2.34e+21 1.20e+22 5.94e+21 1.20e+22 -2.03e+22 9.04e+21 5.94e+21 9.04e+21 2.26e+22 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20160215104146/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 -40 o DIST/3.3 +60 rtr taper w 0.1 hp c 0.03 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 2.0 60 75 15 3.50 0.2913 WVFGRD96 4.0 60 90 10 3.58 0.3375 WVFGRD96 6.0 235 70 -30 3.66 0.3788 WVFGRD96 8.0 235 70 -30 3.73 0.4176 WVFGRD96 10.0 240 90 -25 3.75 0.4405 WVFGRD96 12.0 65 80 25 3.79 0.4739 WVFGRD96 14.0 65 80 25 3.82 0.4964 WVFGRD96 16.0 65 80 20 3.85 0.5154 WVFGRD96 18.0 65 80 20 3.88 0.5328 WVFGRD96 20.0 65 80 20 3.91 0.5483 WVFGRD96 22.0 60 85 20 3.93 0.5637 WVFGRD96 24.0 60 85 20 3.95 0.5784 WVFGRD96 26.0 60 90 20 3.97 0.5923 WVFGRD96 28.0 60 90 20 3.99 0.6085 WVFGRD96 30.0 60 90 20 4.01 0.6240 WVFGRD96 32.0 60 90 20 4.03 0.6359 WVFGRD96 34.0 240 85 -20 4.05 0.6503 WVFGRD96 36.0 240 85 -20 4.07 0.6597 WVFGRD96 38.0 240 85 -20 4.10 0.6669 WVFGRD96 40.0 240 80 -30 4.16 0.6786 WVFGRD96 42.0 240 80 -30 4.18 0.6832 WVFGRD96 44.0 240 80 -30 4.20 0.6848 WVFGRD96 46.0 240 80 -30 4.22 0.6852 WVFGRD96 48.0 240 80 -30 4.23 0.6826 WVFGRD96 50.0 240 80 -30 4.24 0.6791 WVFGRD96 52.0 240 80 -30 4.25 0.6743 WVFGRD96 54.0 240 80 -30 4.26 0.6670 WVFGRD96 56.0 240 80 -30 4.27 0.6590 WVFGRD96 58.0 240 75 -30 4.27 0.6505 WVFGRD96 60.0 240 75 -30 4.28 0.6425 WVFGRD96 62.0 240 75 -30 4.29 0.6332 WVFGRD96 64.0 240 75 -30 4.29 0.6230 WVFGRD96 66.0 235 70 -30 4.30 0.6129 WVFGRD96 68.0 235 70 -30 4.30 0.6022 WVFGRD96 70.0 235 70 -30 4.30 0.5907 WVFGRD96 72.0 235 70 -30 4.31 0.5797 WVFGRD96 74.0 235 65 -30 4.31 0.5685 WVFGRD96 76.0 235 65 -30 4.31 0.5581 WVFGRD96 78.0 235 65 -30 4.31 0.5472 WVFGRD96 80.0 235 65 -30 4.31 0.5371 WVFGRD96 82.0 235 65 -30 4.32 0.5268 WVFGRD96 84.0 65 40 -35 4.41 0.5223 WVFGRD96 86.0 65 40 -35 4.42 0.5204 WVFGRD96 88.0 65 45 -30 4.42 0.5192 WVFGRD96 90.0 65 45 -30 4.42 0.5171 WVFGRD96 92.0 65 45 -30 4.43 0.5154 WVFGRD96 94.0 65 45 -30 4.43 0.5123 WVFGRD96 96.0 65 45 -30 4.44 0.5070 WVFGRD96 98.0 65 45 -30 4.44 0.5022
The best solution is
WVFGRD96 46.0 240 80 -30 4.22 0.6852
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 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 -40 o DIST/3.3 +60 rtr taper w 0.1 hp c 0.03 n 3 lp c 0.07 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 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: