2015/10/13 03:11:37 62.961 -149.340 83.8 4.0 Alaska
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution ENS 2015/10/13 03:11:37:0 62.96 -149.34 83.8 4.0 Alaska Stations used: AK.BPAW AK.BWN AK.CUT AK.DHY AK.GHO AK.KTH AK.MCK AK.MLY AK.RND AK.SCM AK.SKN AK.SSN AK.TRF AK.WRH 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 0.10 n 3 br c 0.12 0.25 n 4 p 2 Best Fitting Double Couple Mo = 1.50e+22 dyne-cm Mw = 4.05 Z = 90 km Plane Strike Dip Rake NP1 285 90 -45 NP2 15 45 -180 Principal Axes: Axis Value Plunge Azimuth T 1.50e+22 30 340 N 0.00e+00 45 105 P -1.50e+22 30 230 Moment Tensor: (dyne-cm) Component Value Mxx 5.29e+21 Mxy -9.16e+21 Mxz 1.02e+22 Myy -5.29e+21 Myz 2.74e+21 Mzz 9.25e+14 #############- ###################--- ####### #############----- ######## T ##############----- ########## ###############------ #############################------- ##############################-------- ################################-------- ---#############################-------- -----------######################--------- ------------------###############--------- ------------------------########---------- -------------------------------#---------- ------------------------------#######--- ------------------------------########## ------- ------------------########## ------ P -----------------########## ----- ----------------########## --------------------########## -----------------########### ------------########## ----########## Global CMT Convention Moment Tensor: R T P 9.25e+14 1.02e+22 -2.74e+21 1.02e+22 5.29e+21 9.16e+21 -2.74e+21 9.16e+21 -5.29e+21 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20151013031137/index.html |
STK = 285 DIP = 90 RAKE = -45 MW = 4.05 HS = 90.0
The NDK file is 20151013031137.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution ENS 2015/10/13 03:11:37:0 62.96 -149.34 83.8 4.0 Alaska Stations used: AK.BPAW AK.BWN AK.CUT AK.DHY AK.GHO AK.KTH AK.MCK AK.MLY AK.RND AK.SCM AK.SKN AK.SSN AK.TRF AK.WRH 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 0.10 n 3 br c 0.12 0.25 n 4 p 2 Best Fitting Double Couple Mo = 1.50e+22 dyne-cm Mw = 4.05 Z = 90 km Plane Strike Dip Rake NP1 285 90 -45 NP2 15 45 -180 Principal Axes: Axis Value Plunge Azimuth T 1.50e+22 30 340 N 0.00e+00 45 105 P -1.50e+22 30 230 Moment Tensor: (dyne-cm) Component Value Mxx 5.29e+21 Mxy -9.16e+21 Mxz 1.02e+22 Myy -5.29e+21 Myz 2.74e+21 Mzz 9.25e+14 #############- ###################--- ####### #############----- ######## T ##############----- ########## ###############------ #############################------- ##############################-------- ################################-------- ---#############################-------- -----------######################--------- ------------------###############--------- ------------------------########---------- -------------------------------#---------- ------------------------------#######--- ------------------------------########## ------- ------------------########## ------ P -----------------########## ----- ----------------########## --------------------########## -----------------########### ------------########## ----########## Global CMT Convention Moment Tensor: R T P 9.25e+14 1.02e+22 -2.74e+21 1.02e+22 5.29e+21 9.16e+21 -2.74e+21 9.16e+21 -5.29e+21 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20151013031137/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:
cut o DIST/3.3 -30 o DIST/3.3 +70 rtr taper w 0.1 hp c 0.03 n 3 lp c 0.10 n 3 br c 0.12 0.25 n 4 p 2The results of this grid search from 0.5 to 19 km depth are as follow:
DEPTH STK DIP RAKE MW FIT WVFGRD96 2.0 175 90 0 3.20 0.3620 WVFGRD96 4.0 80 80 -15 3.32 0.4369 WVFGRD96 6.0 90 55 25 3.42 0.4773 WVFGRD96 8.0 75 55 -30 3.48 0.4974 WVFGRD96 10.0 260 70 -25 3.48 0.5109 WVFGRD96 12.0 260 70 -25 3.51 0.5173 WVFGRD96 14.0 80 75 -15 3.52 0.5209 WVFGRD96 16.0 85 75 15 3.55 0.5289 WVFGRD96 18.0 85 70 15 3.58 0.5330 WVFGRD96 20.0 85 70 15 3.60 0.5366 WVFGRD96 22.0 85 70 15 3.63 0.5374 WVFGRD96 24.0 85 80 20 3.64 0.5366 WVFGRD96 26.0 85 85 25 3.66 0.5386 WVFGRD96 28.0 85 85 25 3.68 0.5440 WVFGRD96 30.0 265 85 -30 3.70 0.5522 WVFGRD96 32.0 265 85 -30 3.72 0.5615 WVFGRD96 34.0 265 80 -30 3.73 0.5654 WVFGRD96 36.0 265 85 -25 3.74 0.5624 WVFGRD96 38.0 265 80 -25 3.76 0.5572 WVFGRD96 40.0 90 80 35 3.84 0.5563 WVFGRD96 42.0 90 80 35 3.86 0.5599 WVFGRD96 44.0 90 80 35 3.88 0.5631 WVFGRD96 46.0 95 75 40 3.91 0.5664 WVFGRD96 48.0 95 75 35 3.91 0.5704 WVFGRD96 50.0 95 75 35 3.92 0.5750 WVFGRD96 52.0 95 75 35 3.93 0.5779 WVFGRD96 54.0 90 90 35 3.92 0.5821 WVFGRD96 56.0 90 90 35 3.93 0.5866 WVFGRD96 58.0 270 90 -35 3.93 0.5932 WVFGRD96 60.0 110 65 30 3.98 0.5973 WVFGRD96 62.0 100 85 40 3.96 0.6063 WVFGRD96 64.0 100 85 40 3.97 0.6135 WVFGRD96 66.0 100 90 45 3.98 0.6220 WVFGRD96 68.0 280 90 -45 3.99 0.6282 WVFGRD96 70.0 105 85 45 4.00 0.6359 WVFGRD96 72.0 105 85 45 4.01 0.6437 WVFGRD96 74.0 105 85 45 4.02 0.6494 WVFGRD96 76.0 105 85 45 4.02 0.6543 WVFGRD96 78.0 105 85 45 4.03 0.6577 WVFGRD96 80.0 285 90 -45 4.03 0.6595 WVFGRD96 82.0 285 90 -45 4.03 0.6643 WVFGRD96 84.0 105 90 45 4.04 0.6670 WVFGRD96 86.0 105 90 45 4.04 0.6684 WVFGRD96 88.0 105 90 45 4.05 0.6699 WVFGRD96 90.0 285 90 -45 4.05 0.6707 WVFGRD96 92.0 105 90 40 4.05 0.6700 WVFGRD96 94.0 105 90 40 4.05 0.6699 WVFGRD96 96.0 105 90 40 4.05 0.6688 WVFGRD96 98.0 285 90 -40 4.06 0.6689 WVFGRD96 100.0 105 90 40 4.06 0.6678 WVFGRD96 102.0 285 90 -40 4.07 0.6669 WVFGRD96 104.0 285 90 -40 4.07 0.6658 WVFGRD96 106.0 105 90 40 4.07 0.6640 WVFGRD96 108.0 105 90 35 4.07 0.6627 WVFGRD96 110.0 105 90 35 4.07 0.6613 WVFGRD96 112.0 105 90 35 4.08 0.6585 WVFGRD96 114.0 285 90 -35 4.08 0.6573 WVFGRD96 116.0 285 90 -35 4.08 0.6561 WVFGRD96 118.0 285 90 -35 4.09 0.6535
The best solution is
WVFGRD96 90.0 285 90 -45 4.05 0.6707
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 o DIST/3.3 -30 o DIST/3.3 +70 rtr taper w 0.1 hp c 0.03 n 3 lp c 0.10 n 3 br c 0.12 0.25 n 4 p 2
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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: