2012/10/25 12:57:36 63.781 -148.382 10.1 3.50 Alaska
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution ENS 2012/10/25 12:57:36:0 63.78 -148.38 10.1 3.5 Alaska Stations used: AK.BMR AK.BPAW AK.BWN AK.CCB AK.DOT AK.EYAK AK.FID AK.FYU AK.GLI AK.GLM AK.HDA AK.HIN AK.KLU AK.MCK AK.MLY AK.NEA AK.PIN AK.PPD AK.PPLA AK.RAG AK.RC01 AK.RIDG AK.RND AK.SAW AK.SCM AK.TRF AK.WRH AK.YAH IU.COLA US.EGAK Filtering commands used: hp c 0.02 n 3 lp c 0.10 n 3 br c 0.12 0.25 n 4 p 2 Best Fitting Double Couple Mo = 2.40e+21 dyne-cm Mw = 3.52 Z = 17 km Plane Strike Dip Rake NP1 81 61 96 NP2 250 30 80 Principal Axes: Axis Value Plunge Azimuth T 2.40e+21 74 6 N 0.00e+00 5 259 P -2.40e+21 15 167 Moment Tensor: (dyne-cm) Component Value Mxx -1.94e+21 Mxy 4.98e+20 Mxz 1.23e+21 Myy -1.05e+20 Myz -6.50e+19 Mzz 2.05e+21 -------------- ---------------------- ---------------------------- ----------###############----- --------#######################--- ------#############################- -----################################# -----############## ################## ---################ T ################## ---################# ##################- ---#####################################-- --####################################---- --#################################------- --#############################--------- ------####################-------------- -------------------------------------- ------------------------------------ ---------------------------------- ------------------------------ ---------------- --------- ------------- P ------ --------- -- Global CMT Convention Moment Tensor: R T P 2.05e+21 1.23e+21 6.50e+19 1.23e+21 -1.94e+21 -4.98e+20 6.50e+19 -4.98e+20 -1.05e+20 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20121025125736/index.html |
STK = 250 DIP = 30 RAKE = 80 MW = 3.52 HS = 17.0
The NDK file is 20121025125736.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution ENS 2012/10/25 12:57:36:0 63.78 -148.38 10.1 3.5 Alaska Stations used: AK.BMR AK.BPAW AK.BWN AK.CCB AK.DOT AK.EYAK AK.FID AK.FYU AK.GLI AK.GLM AK.HDA AK.HIN AK.KLU AK.MCK AK.MLY AK.NEA AK.PIN AK.PPD AK.PPLA AK.RAG AK.RC01 AK.RIDG AK.RND AK.SAW AK.SCM AK.TRF AK.WRH AK.YAH IU.COLA US.EGAK Filtering commands used: hp c 0.02 n 3 lp c 0.10 n 3 br c 0.12 0.25 n 4 p 2 Best Fitting Double Couple Mo = 2.40e+21 dyne-cm Mw = 3.52 Z = 17 km Plane Strike Dip Rake NP1 81 61 96 NP2 250 30 80 Principal Axes: Axis Value Plunge Azimuth T 2.40e+21 74 6 N 0.00e+00 5 259 P -2.40e+21 15 167 Moment Tensor: (dyne-cm) Component Value Mxx -1.94e+21 Mxy 4.98e+20 Mxz 1.23e+21 Myy -1.05e+20 Myz -6.50e+19 Mzz 2.05e+21 -------------- ---------------------- ---------------------------- ----------###############----- --------#######################--- ------#############################- -----################################# -----############## ################## ---################ T ################## ---################# ##################- ---#####################################-- --####################################---- --#################################------- --#############################--------- ------####################-------------- -------------------------------------- ------------------------------------ ---------------------------------- ------------------------------ ---------------- --------- ------------- P ------ --------- -- Global CMT Convention Moment Tensor: R T P 2.05e+21 1.23e+21 6.50e+19 1.23e+21 -1.94e+21 -4.98e+20 6.50e+19 -4.98e+20 -1.05e+20 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20121025125736/index.html |
USGS/SLU Regional Moment Solution 12/10/25 12:57:36.35 Epicenter: 63.747 -148.436 MW 3.6 USGS/SLU REGIONAL MOMENT TENSOR Depth 20 No. of sta: 35 Moment Tensor; Scale 10**14 Nm Mrr= 2.19 Mtt=-2.36 Mpp= 0.17 Mrt= 0.76 Mrp= 1.30 Mtp=-0.17 Principal axes: T Val= 2.90 Plg=64 Azm=286 N -0.35 23 76 P -2.54 11 171 Best Double Couple:Mo=2.7*10**14 NP1:Strike=287 Dip=39 Slip= 128 NP2: 62 60 63 |
(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 0.10 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 0.5 90 45 -90 3.14 0.3911 WVFGRD96 1.0 90 45 -90 3.08 0.2489 WVFGRD96 2.0 90 45 -90 3.28 0.4058 WVFGRD96 3.0 305 60 -35 3.29 0.2702 WVFGRD96 4.0 -5 25 -15 3.35 0.3054 WVFGRD96 5.0 210 -10 25 3.39 0.4361 WVFGRD96 6.0 210 -10 25 3.39 0.5178 WVFGRD96 7.0 205 15 25 3.38 0.5587 WVFGRD96 8.0 220 10 40 3.46 0.5792 WVFGRD96 9.0 235 15 55 3.46 0.5992 WVFGRD96 10.0 240 20 65 3.47 0.6167 WVFGRD96 11.0 240 25 70 3.49 0.6316 WVFGRD96 12.0 240 25 70 3.49 0.6450 WVFGRD96 13.0 250 25 80 3.49 0.6552 WVFGRD96 14.0 245 30 75 3.50 0.6624 WVFGRD96 15.0 245 30 75 3.51 0.6671 WVFGRD96 16.0 250 30 80 3.51 0.6687 WVFGRD96 17.0 250 30 80 3.52 0.6688 WVFGRD96 18.0 250 30 80 3.53 0.6668 WVFGRD96 19.0 250 30 80 3.54 0.6631 WVFGRD96 20.0 255 30 85 3.55 0.6580 WVFGRD96 21.0 255 30 85 3.56 0.6516 WVFGRD96 22.0 80 60 90 3.57 0.6436 WVFGRD96 23.0 80 60 90 3.58 0.6337 WVFGRD96 24.0 75 60 85 3.60 0.6220 WVFGRD96 25.0 75 60 85 3.60 0.6084 WVFGRD96 26.0 75 60 85 3.61 0.5924 WVFGRD96 27.0 75 60 85 3.61 0.5740 WVFGRD96 28.0 75 60 80 3.62 0.5549 WVFGRD96 29.0 75 60 80 3.63 0.5346
The best solution is
WVFGRD96 17.0 250 30 80 3.52 0.6688
The mechanism corresponding 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 0.10 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: