2012/09/13 05:58:04 59.610 -153.130 102.5 4.00 Alaska
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2012/09/13 05:58:04:0 59.61 -153.13 102.5 4.0 Alaska
Stations used:
AK.BRLK AK.CNP AK.FIB AK.HOM AK.RC01 AK.SSN AT.SVW2 II.KDAK
Filtering commands used:
hp c 0.03 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 1.66e+22 dyne-cm
Mw = 4.08
Z = 121 km
Plane Strike Dip Rake
NP1 65 65 55
NP2 304 42 141
Principal Axes:
Axis Value Plunge Azimuth
T 1.66e+22 55 289
N 0.00e+00 31 81
P -1.66e+22 13 180
Moment Tensor: (dyne-cm)
Component Value
Mxx -1.52e+22
Mxy -1.56e+21
Mxz 6.22e+21
Myy 4.75e+21
Myz -7.34e+21
Mzz 1.04e+22
--------------
----------------------
----------------------------
----########------------------
-###################--------------
########################------------
############################----------
###############################-------##
########## ###################----####
########### T #####################-######
########### ####################--######
################################-----#####
#############################---------####
#########################------------###
#####################----------------###
###############---------------------##
-----------------------------------#
----------------------------------
------------------------------
------------- ------------
---------- P ---------
------ -----
Global CMT Convention Moment Tensor:
R T P
1.04e+22 6.22e+21 7.34e+21
6.22e+21 -1.52e+22 1.56e+21
7.34e+21 1.56e+21 4.75e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20120913055804/index.html
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STK = 65
DIP = 65
RAKE = 55
MW = 4.08
HS = 121.0
The NDK file is 20120913055804.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2012/09/13 05:58:04:0 59.61 -153.13 102.5 4.0 Alaska
Stations used:
AK.BRLK AK.CNP AK.FIB AK.HOM AK.RC01 AK.SSN AT.SVW2 II.KDAK
Filtering commands used:
hp c 0.03 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 1.66e+22 dyne-cm
Mw = 4.08
Z = 121 km
Plane Strike Dip Rake
NP1 65 65 55
NP2 304 42 141
Principal Axes:
Axis Value Plunge Azimuth
T 1.66e+22 55 289
N 0.00e+00 31 81
P -1.66e+22 13 180
Moment Tensor: (dyne-cm)
Component Value
Mxx -1.52e+22
Mxy -1.56e+21
Mxz 6.22e+21
Myy 4.75e+21
Myz -7.34e+21
Mzz 1.04e+22
--------------
----------------------
----------------------------
----########------------------
-###################--------------
########################------------
############################----------
###############################-------##
########## ###################----####
########### T #####################-######
########### ####################--######
################################-----#####
#############################---------####
#########################------------###
#####################----------------###
###############---------------------##
-----------------------------------#
----------------------------------
------------------------------
------------- ------------
---------- P ---------
------ -----
Global CMT Convention Moment Tensor:
R T P
1.04e+22 6.22e+21 7.34e+21
6.22e+21 -1.52e+22 1.56e+21
7.34e+21 1.56e+21 4.75e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20120913055804/index.html
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(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.
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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 0.03 n 3 lp c 0.10 n 3The results of this grid search from 0.5 to 19 km depth are as follow:
DEPTH STK DIP RAKE MW FIT
WVFGRD96 0.5 330 40 -10 2.99 0.1040
WVFGRD96 1.0 330 55 -10 2.95 0.1120
WVFGRD96 2.0 135 55 -60 3.19 0.1497
WVFGRD96 3.0 135 55 -60 3.23 0.1663
WVFGRD96 4.0 325 50 -35 3.22 0.1773
WVFGRD96 5.0 330 55 -25 3.23 0.1879
WVFGRD96 6.0 335 60 -15 3.24 0.1919
WVFGRD96 7.0 335 60 -15 3.27 0.1969
WVFGRD96 8.0 335 55 -5 3.32 0.1936
WVFGRD96 9.0 335 55 0 3.35 0.1946
WVFGRD96 10.0 340 55 10 3.37 0.1935
WVFGRD96 11.0 155 90 25 3.37 0.1876
WVFGRD96 12.0 160 80 25 3.38 0.1835
WVFGRD96 13.0 70 75 25 3.41 0.1814
WVFGRD96 14.0 70 70 20 3.42 0.1824
WVFGRD96 15.0 70 70 20 3.44 0.1833
WVFGRD96 16.0 60 80 -15 3.46 0.1886
WVFGRD96 17.0 60 80 -15 3.48 0.1934
WVFGRD96 18.0 60 80 -15 3.50 0.1988
WVFGRD96 19.0 60 80 -15 3.51 0.2036
WVFGRD96 20.0 60 80 -15 3.52 0.2096
WVFGRD96 21.0 60 80 -15 3.54 0.2152
WVFGRD96 22.0 60 80 -10 3.55 0.2188
WVFGRD96 23.0 60 80 -10 3.57 0.2249
WVFGRD96 24.0 65 85 -5 3.56 0.2312
WVFGRD96 25.0 65 80 -5 3.57 0.2361
WVFGRD96 26.0 65 80 0 3.58 0.2426
WVFGRD96 27.0 255 60 30 3.63 0.2460
WVFGRD96 28.0 250 65 25 3.64 0.2542
WVFGRD96 29.0 250 65 25 3.65 0.2616
WVFGRD96 30.0 250 65 25 3.66 0.2668
WVFGRD96 31.0 250 65 25 3.67 0.2721
WVFGRD96 32.0 255 65 30 3.66 0.2758
WVFGRD96 33.0 255 65 30 3.67 0.2795
WVFGRD96 34.0 250 70 25 3.68 0.2831
WVFGRD96 35.0 250 70 25 3.69 0.2853
WVFGRD96 36.0 245 90 0 3.67 0.2893
WVFGRD96 37.0 245 90 0 3.69 0.2930
WVFGRD96 38.0 245 90 0 3.70 0.2956
WVFGRD96 39.0 65 85 0 3.73 0.2982
WVFGRD96 40.0 65 80 -5 3.75 0.2994
WVFGRD96 41.0 65 85 -5 3.76 0.2993
WVFGRD96 42.0 65 85 -10 3.78 0.2980
WVFGRD96 43.0 65 85 -10 3.79 0.2964
WVFGRD96 44.0 65 85 -10 3.80 0.2952
WVFGRD96 45.0 60 85 -10 3.84 0.2936
WVFGRD96 46.0 60 85 -10 3.85 0.2921
WVFGRD96 47.0 240 90 0 3.86 0.2918
WVFGRD96 48.0 240 90 0 3.86 0.2920
WVFGRD96 49.0 60 90 0 3.87 0.2919
WVFGRD96 50.0 60 90 0 3.88 0.2914
WVFGRD96 51.0 60 90 0 3.88 0.2906
WVFGRD96 52.0 65 75 15 3.87 0.2924
WVFGRD96 53.0 240 90 -5 3.89 0.2932
WVFGRD96 54.0 65 75 15 3.88 0.2958
WVFGRD96 55.0 65 75 15 3.88 0.2977
WVFGRD96 56.0 60 80 20 3.92 0.3028
WVFGRD96 57.0 60 80 20 3.92 0.3079
WVFGRD96 58.0 60 80 20 3.93 0.3114
WVFGRD96 59.0 60 80 20 3.93 0.3157
WVFGRD96 60.0 60 80 20 3.94 0.3210
WVFGRD96 61.0 60 80 20 3.94 0.3244
WVFGRD96 62.0 60 80 20 3.94 0.3284
WVFGRD96 63.0 60 80 20 3.95 0.3324
WVFGRD96 64.0 60 75 15 3.97 0.3341
WVFGRD96 65.0 60 75 20 3.97 0.3385
WVFGRD96 66.0 60 75 15 3.98 0.3417
WVFGRD96 67.0 60 75 20 3.98 0.3447
WVFGRD96 68.0 60 75 20 3.98 0.3483
WVFGRD96 69.0 60 75 20 3.98 0.3488
WVFGRD96 70.0 60 75 20 3.99 0.3535
WVFGRD96 71.0 60 75 20 3.99 0.3548
WVFGRD96 72.0 55 85 25 3.99 0.3581
WVFGRD96 73.0 55 85 25 4.00 0.3600
WVFGRD96 74.0 55 85 25 4.00 0.3632
WVFGRD96 75.0 55 85 25 4.00 0.3650
WVFGRD96 76.0 55 85 25 4.00 0.3669
WVFGRD96 77.0 55 85 30 4.00 0.3685
WVFGRD96 78.0 55 85 25 4.00 0.3706
WVFGRD96 79.0 55 85 30 4.00 0.3715
WVFGRD96 80.0 55 80 30 4.03 0.3737
WVFGRD96 81.0 55 80 30 4.03 0.3754
WVFGRD96 82.0 55 80 30 4.03 0.3770
WVFGRD96 83.0 55 80 30 4.03 0.3784
WVFGRD96 84.0 55 80 35 4.03 0.3809
WVFGRD96 85.0 60 70 30 4.04 0.3808
WVFGRD96 86.0 60 70 30 4.04 0.3845
WVFGRD96 87.0 60 70 30 4.04 0.3848
WVFGRD96 88.0 60 70 35 4.04 0.3879
WVFGRD96 89.0 60 70 35 4.05 0.3893
WVFGRD96 90.0 60 70 35 4.05 0.3906
WVFGRD96 91.0 60 70 40 4.05 0.3932
WVFGRD96 92.0 60 70 40 4.05 0.3936
WVFGRD96 93.0 60 70 40 4.05 0.3972
WVFGRD96 94.0 60 70 40 4.05 0.3973
WVFGRD96 95.0 60 70 45 4.05 0.3996
WVFGRD96 96.0 60 70 45 4.06 0.4019
WVFGRD96 97.0 60 70 45 4.06 0.4025
WVFGRD96 98.0 60 70 45 4.06 0.4054
WVFGRD96 99.0 60 70 45 4.06 0.4053
WVFGRD96 100.0 60 70 45 4.06 0.4072
WVFGRD96 101.0 65 65 45 4.06 0.4088
WVFGRD96 102.0 60 70 50 4.06 0.4085
WVFGRD96 103.0 60 70 50 4.06 0.4114
WVFGRD96 104.0 60 70 50 4.07 0.4121
WVFGRD96 105.0 60 70 50 4.07 0.4127
WVFGRD96 106.0 60 70 50 4.07 0.4151
WVFGRD96 107.0 60 70 50 4.07 0.4141
WVFGRD96 108.0 65 65 50 4.07 0.4161
WVFGRD96 109.0 65 65 50 4.07 0.4166
WVFGRD96 110.0 65 65 50 4.07 0.4174
WVFGRD96 111.0 65 65 50 4.07 0.4175
WVFGRD96 112.0 65 65 50 4.07 0.4196
WVFGRD96 113.0 65 65 50 4.07 0.4182
WVFGRD96 114.0 65 65 50 4.07 0.4200
WVFGRD96 115.0 65 65 50 4.08 0.4201
WVFGRD96 116.0 65 65 55 4.08 0.4193
WVFGRD96 117.0 65 65 55 4.08 0.4210
WVFGRD96 118.0 65 65 55 4.08 0.4211
WVFGRD96 119.0 65 65 55 4.08 0.4204
WVFGRD96 120.0 65 65 55 4.08 0.4213
WVFGRD96 121.0 65 65 55 4.08 0.4218
WVFGRD96 122.0 65 65 55 4.08 0.4201
WVFGRD96 123.0 65 65 55 4.08 0.4215
WVFGRD96 124.0 65 65 55 4.08 0.4209
WVFGRD96 125.0 65 65 55 4.09 0.4203
WVFGRD96 126.0 65 65 55 4.09 0.4199
WVFGRD96 127.0 65 65 60 4.09 0.4199
WVFGRD96 128.0 65 65 60 4.09 0.4199
WVFGRD96 129.0 65 65 60 4.09 0.4175
The best solution is
WVFGRD96 121.0 65 65 55 4.08 0.4218
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 0.03 n 3 lp c 0.10 n 3
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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: