2011/07/28 14:00:00 62.050 -151.290 81 5.30 Alask
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution ENS 2011/07/28 14:00:00:8 62.05 -151.29 81.0 5.3 Alask Stations used: AK.BAL AK.BMR AK.BRLK AK.CAST AK.CCB AK.CHUM AK.CNP AK.COLD AK.CRQ AK.CTG AK.DHY AK.DIV AK.EYAK AK.FIB AK.FID AK.FYU AK.GHO AK.HOM AK.KLU AK.KNK AK.KTH AK.MCK AK.MDM AK.MLY AK.PAX AK.PPLA AK.RAG AK.RC01 AK.RND AK.SAW AK.SCM AK.SSN AK.SWD AK.TGL AK.TRF AK.WRH AT.MENT AT.OHAK AT.PMR AT.SVW2 IU.COLA US.EGAK Filtering commands used: hp c 0.02 n 3 lp c 0.06 n 3 Best Fitting Double Couple Mo = 8.51e+23 dyne-cm Mw = 5.22 Z = 85 km Plane Strike Dip Rake NP1 348 70 105 NP2 130 25 55 Principal Axes: Axis Value Plunge Azimuth T 8.51e+23 62 281 N 0.00e+00 14 162 P -8.51e+23 23 66 Moment Tensor: (dyne-cm) Component Value Mxx -1.10e+23 Mxy -2.99e+23 Mxz -5.89e+22 Myy -4.24e+23 Myz -6.27e+23 Mzz 5.34e+23 ###----------- #########------------- #############--------------- ###############--------------- ##################---------------- -###################---------------- -#####################---------- --- --######################--------- P ---- --######################--------- ---- ---########## ##########---------------- ---########## T ##########---------------- ----######### ##########---------------- ----#######################--------------- ----######################-------------- -----#####################-------------- -----####################------------- ------##################------------ -------################----------- -------##############--------- ----------##########------## ----------------###### ------------## Global CMT Convention Moment Tensor: R T P 5.34e+23 -5.89e+22 6.27e+23 -5.89e+22 -1.10e+23 2.99e+23 6.27e+23 2.99e+23 -4.24e+23 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20110728140000/index.html |
STK = 130 DIP = 25 RAKE = 55 MW = 5.22 HS = 85.0
The NDK file is 20110728140000.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution ENS 2011/07/28 14:00:00:8 62.05 -151.29 81.0 5.3 Alask Stations used: AK.BAL AK.BMR AK.BRLK AK.CAST AK.CCB AK.CHUM AK.CNP AK.COLD AK.CRQ AK.CTG AK.DHY AK.DIV AK.EYAK AK.FIB AK.FID AK.FYU AK.GHO AK.HOM AK.KLU AK.KNK AK.KTH AK.MCK AK.MDM AK.MLY AK.PAX AK.PPLA AK.RAG AK.RC01 AK.RND AK.SAW AK.SCM AK.SSN AK.SWD AK.TGL AK.TRF AK.WRH AT.MENT AT.OHAK AT.PMR AT.SVW2 IU.COLA US.EGAK Filtering commands used: hp c 0.02 n 3 lp c 0.06 n 3 Best Fitting Double Couple Mo = 8.51e+23 dyne-cm Mw = 5.22 Z = 85 km Plane Strike Dip Rake NP1 348 70 105 NP2 130 25 55 Principal Axes: Axis Value Plunge Azimuth T 8.51e+23 62 281 N 0.00e+00 14 162 P -8.51e+23 23 66 Moment Tensor: (dyne-cm) Component Value Mxx -1.10e+23 Mxy -2.99e+23 Mxz -5.89e+22 Myy -4.24e+23 Myz -6.27e+23 Mzz 5.34e+23 ###----------- #########------------- #############--------------- ###############--------------- ##################---------------- -###################---------------- -#####################---------- --- --######################--------- P ---- --######################--------- ---- ---########## ##########---------------- ---########## T ##########---------------- ----######### ##########---------------- ----#######################--------------- ----######################-------------- -----#####################-------------- -----####################------------- ------##################------------ -------################----------- -------##############--------- ----------##########------## ----------------###### ------------## Global CMT Convention Moment Tensor: R T P 5.34e+23 -5.89e+22 6.27e+23 -5.89e+22 -1.10e+23 2.99e+23 6.27e+23 2.99e+23 -4.24e+23 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20110728140000/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:
hp c 0.02 n 3 lp c 0.06 n 3The results of this grid search from 0.5 to 19 km depth are as follow:
DEPTH STK DIP RAKE MW FIT WVFGRD96 1.0 35 45 -75 4.35 0.1855 WVFGRD96 3.0 35 50 -70 4.52 0.2300 WVFGRD96 4.0 45 55 -55 4.53 0.2169 WVFGRD96 7.0 70 80 30 4.53 0.2295 WVFGRD96 9.0 70 80 35 4.58 0.2378 WVFGRD96 11.0 70 75 35 4.60 0.2434 WVFGRD96 13.0 70 75 30 4.62 0.2443 WVFGRD96 15.0 250 60 35 4.65 0.2465 WVFGRD96 17.0 250 60 35 4.66 0.2509 WVFGRD96 19.0 250 60 35 4.68 0.2525 WVFGRD96 21.0 250 65 35 4.69 0.2511 WVFGRD96 23.0 250 65 35 4.70 0.2504 WVFGRD96 25.0 250 65 35 4.72 0.2506 WVFGRD96 27.0 255 60 40 4.73 0.2483 WVFGRD96 29.0 255 60 40 4.75 0.2458 WVFGRD96 31.0 80 80 20 4.77 0.2480 WVFGRD96 33.0 80 80 20 4.79 0.2566 WVFGRD96 35.0 85 70 15 4.82 0.2651 WVFGRD96 37.0 85 70 15 4.84 0.2738 WVFGRD96 39.0 85 70 10 4.87 0.2819 WVFGRD96 41.0 80 40 -15 4.94 0.2843 WVFGRD96 43.0 80 40 -15 4.96 0.2900 WVFGRD96 45.0 85 40 0 4.99 0.3014 WVFGRD96 47.0 85 35 0 5.01 0.3137 WVFGRD96 49.0 90 35 5 5.02 0.3273 WVFGRD96 51.0 90 35 5 5.04 0.3400 WVFGRD96 53.0 90 35 10 5.06 0.3532 WVFGRD96 55.0 95 35 15 5.07 0.3646 WVFGRD96 57.0 95 35 20 5.09 0.3764 WVFGRD96 59.0 100 30 25 5.11 0.3914 WVFGRD96 61.0 100 30 25 5.12 0.4059 WVFGRD96 63.0 120 20 40 5.14 0.4222 WVFGRD96 65.0 125 20 50 5.16 0.4405 WVFGRD96 67.0 125 20 50 5.17 0.4573 WVFGRD96 69.0 125 20 50 5.18 0.4717 WVFGRD96 70.0 130 20 55 5.19 0.4784 WVFGRD96 71.0 130 20 55 5.19 0.4845 WVFGRD96 72.0 130 20 55 5.20 0.4897 WVFGRD96 73.0 130 20 55 5.20 0.4945 WVFGRD96 74.0 130 20 55 5.20 0.4989 WVFGRD96 75.0 130 20 55 5.21 0.5024 WVFGRD96 76.0 135 20 60 5.21 0.5062 WVFGRD96 77.0 135 20 60 5.21 0.5087 WVFGRD96 78.0 125 25 50 5.21 0.5114 WVFGRD96 79.0 125 25 50 5.21 0.5133 WVFGRD96 80.0 130 25 55 5.22 0.5157 WVFGRD96 81.0 130 25 55 5.22 0.5171 WVFGRD96 82.0 130 25 55 5.22 0.5183 WVFGRD96 83.0 130 25 55 5.22 0.5191 WVFGRD96 84.0 130 25 55 5.22 0.5195 WVFGRD96 85.0 130 25 55 5.22 0.5195 WVFGRD96 86.0 130 25 55 5.23 0.5190 WVFGRD96 87.0 130 25 55 5.23 0.5186 WVFGRD96 88.0 130 25 55 5.23 0.5179 WVFGRD96 89.0 130 25 55 5.23 0.5163 WVFGRD96 90.0 130 25 55 5.23 0.5152 WVFGRD96 91.0 130 25 55 5.23 0.5132 WVFGRD96 92.0 130 25 55 5.23 0.5115 WVFGRD96 93.0 130 25 55 5.23 0.5095 WVFGRD96 94.0 130 25 55 5.23 0.5067 WVFGRD96 95.0 130 25 55 5.23 0.5047 WVFGRD96 96.0 130 25 55 5.23 0.5016 WVFGRD96 97.0 130 25 55 5.23 0.4989 WVFGRD96 98.0 130 25 55 5.23 0.4959 WVFGRD96 99.0 130 25 55 5.23 0.4927 WVFGRD96 100.0 135 25 60 5.23 0.4895 WVFGRD96 101.0 135 25 60 5.23 0.4866 WVFGRD96 102.0 135 25 60 5.23 0.4828 WVFGRD96 103.0 135 25 60 5.23 0.4799 WVFGRD96 104.0 135 25 60 5.23 0.4762 WVFGRD96 105.0 135 25 60 5.23 0.4727 WVFGRD96 106.0 135 25 60 5.23 0.4690 WVFGRD96 107.0 135 25 60 5.23 0.4656 WVFGRD96 108.0 135 25 60 5.23 0.4615 WVFGRD96 109.0 135 25 60 5.23 0.4581 WVFGRD96 111.0 135 25 60 5.23 0.4509 WVFGRD96 113.0 135 25 60 5.23 0.4444 WVFGRD96 115.0 135 25 60 5.23 0.4372 WVFGRD96 117.0 130 30 60 5.23 0.4305 WVFGRD96 119.0 130 30 60 5.23 0.4237 WVFGRD96 121.0 130 30 60 5.23 0.4169 WVFGRD96 123.0 130 30 60 5.23 0.4106 WVFGRD96 125.0 130 30 60 5.23 0.4038 WVFGRD96 127.0 140 25 70 5.22 0.3974 WVFGRD96 129.0 140 25 70 5.22 0.3908
The best solution is
WVFGRD96 85.0 130 25 55 5.22 0.5195
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
hp c 0.02 n 3 lp c 0.06 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: