2012/07/06 01:22:04 61.671 -131.239 78.0 4.30 Alaska
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2012/07/06 01:22:04:0 61.67 -131.24 78.0 4.3 Alaska
Stations used:
AK.BRLK AK.CNP AK.FIB AK.GHO AK.HOM AK.PPLA AK.RC01 AK.SAW
AK.SCM AK.SKN AK.SSN AT.PMR
Filtering commands used:
hp c 0.02 n 3
lp c 0.06 n 3
Best Fitting Double Couple
Mo = 1.19e+23 dyne-cm
Mw = 4.65
Z = 87 km
Plane Strike Dip Rake
NP1 65 65 40
NP2 315 54 149
Principal Axes:
Axis Value Plunge Azimuth
T 1.19e+23 45 285
N 0.00e+00 44 92
P -1.19e+23 6 188
Moment Tensor: (dyne-cm)
Component Value
Mxx -1.11e+23
Mxy -3.06e+22
Mxz 2.82e+22
Myy 5.28e+22
Myz -5.56e+22
Mzz 5.85e+22
--------------
----------------------
----------------------------
##########--------------------
################------------------
####################----------------
#######################---------------
##########################------------##
######## #################--------####
######### T ##################------######
######### ####################--########
################################-#########
#############################-----########
#########################--------#######
#####################-------------######
###############-------------------####
---------------------------------###
--------------------------------##
------------------------------
----------------------------
------- ------------
--- P --------
Global CMT Convention Moment Tensor:
R T P
5.85e+22 2.82e+22 5.56e+22
2.82e+22 -1.11e+23 3.06e+22
5.56e+22 3.06e+22 5.28e+22
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20120706012204/index.html
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STK = 65
DIP = 65
RAKE = 40
MW = 4.65
HS = 87.0
The NDK file is 20120706012204.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2012/07/06 01:22:04:0 61.67 -131.24 78.0 4.3 Alaska
Stations used:
AK.BRLK AK.CNP AK.FIB AK.GHO AK.HOM AK.PPLA AK.RC01 AK.SAW
AK.SCM AK.SKN AK.SSN AT.PMR
Filtering commands used:
hp c 0.02 n 3
lp c 0.06 n 3
Best Fitting Double Couple
Mo = 1.19e+23 dyne-cm
Mw = 4.65
Z = 87 km
Plane Strike Dip Rake
NP1 65 65 40
NP2 315 54 149
Principal Axes:
Axis Value Plunge Azimuth
T 1.19e+23 45 285
N 0.00e+00 44 92
P -1.19e+23 6 188
Moment Tensor: (dyne-cm)
Component Value
Mxx -1.11e+23
Mxy -3.06e+22
Mxz 2.82e+22
Myy 5.28e+22
Myz -5.56e+22
Mzz 5.85e+22
--------------
----------------------
----------------------------
##########--------------------
################------------------
####################----------------
#######################---------------
##########################------------##
######## #################--------####
######### T ##################------######
######### ####################--########
################################-#########
#############################-----########
#########################--------#######
#####################-------------######
###############-------------------####
---------------------------------###
--------------------------------##
------------------------------
----------------------------
------- ------------
--- P --------
Global CMT Convention Moment Tensor:
R T P
5.85e+22 2.82e+22 5.56e+22
2.82e+22 -1.11e+23 3.06e+22
5.56e+22 3.06e+22 5.28e+22
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20120706012204/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 0.02 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 0.5 85 40 65 3.82 0.1911
WVFGRD96 1.0 60 80 15 3.75 0.1965
WVFGRD96 2.0 55 90 20 3.87 0.2723
WVFGRD96 3.0 35 70 25 3.93 0.3088
WVFGRD96 4.0 215 90 -25 3.95 0.3298
WVFGRD96 5.0 40 90 25 3.98 0.3549
WVFGRD96 6.0 45 85 25 4.01 0.3770
WVFGRD96 7.0 45 85 25 4.03 0.3956
WVFGRD96 8.0 45 85 25 4.07 0.4108
WVFGRD96 9.0 55 85 30 4.10 0.4207
WVFGRD96 10.0 55 85 25 4.11 0.4349
WVFGRD96 11.0 235 90 -25 4.13 0.4466
WVFGRD96 12.0 55 85 25 4.14 0.4578
WVFGRD96 13.0 55 90 25 4.15 0.4661
WVFGRD96 14.0 55 90 25 4.16 0.4726
WVFGRD96 15.0 55 90 20 4.18 0.4790
WVFGRD96 16.0 55 90 20 4.19 0.4841
WVFGRD96 17.0 55 90 20 4.19 0.4883
WVFGRD96 18.0 55 90 20 4.20 0.4929
WVFGRD96 19.0 60 85 20 4.22 0.4965
WVFGRD96 20.0 60 85 20 4.23 0.5005
WVFGRD96 21.0 60 85 20 4.24 0.5033
WVFGRD96 22.0 60 85 20 4.25 0.5061
WVFGRD96 23.0 60 85 20 4.26 0.5092
WVFGRD96 24.0 60 85 20 4.26 0.5117
WVFGRD96 25.0 60 85 20 4.27 0.5139
WVFGRD96 26.0 240 90 -20 4.28 0.5145
WVFGRD96 27.0 60 85 20 4.28 0.5174
WVFGRD96 28.0 240 90 -20 4.30 0.5181
WVFGRD96 29.0 240 90 -20 4.30 0.5199
WVFGRD96 30.0 60 90 20 4.31 0.5214
WVFGRD96 31.0 240 90 -20 4.32 0.5221
WVFGRD96 32.0 60 90 20 4.33 0.5229
WVFGRD96 33.0 60 90 20 4.34 0.5239
WVFGRD96 34.0 60 90 20 4.34 0.5244
WVFGRD96 35.0 60 90 20 4.35 0.5244
WVFGRD96 36.0 60 90 20 4.36 0.5239
WVFGRD96 37.0 60 90 20 4.38 0.5233
WVFGRD96 38.0 240 90 -20 4.39 0.5224
WVFGRD96 39.0 60 90 20 4.40 0.5215
WVFGRD96 40.0 60 90 30 4.45 0.5219
WVFGRD96 41.0 60 90 25 4.46 0.5182
WVFGRD96 42.0 240 90 -25 4.46 0.5153
WVFGRD96 43.0 60 90 25 4.47 0.5125
WVFGRD96 44.0 240 90 -25 4.48 0.5099
WVFGRD96 45.0 60 85 30 4.48 0.5078
WVFGRD96 46.0 240 90 -30 4.49 0.5048
WVFGRD96 47.0 60 85 30 4.49 0.5051
WVFGRD96 48.0 60 85 30 4.50 0.5047
WVFGRD96 49.0 60 85 30 4.50 0.5043
WVFGRD96 50.0 65 65 35 4.50 0.5072
WVFGRD96 51.0 65 65 35 4.51 0.5113
WVFGRD96 52.0 65 65 35 4.51 0.5152
WVFGRD96 53.0 65 65 35 4.52 0.5193
WVFGRD96 54.0 65 65 35 4.53 0.5244
WVFGRD96 55.0 65 65 35 4.53 0.5302
WVFGRD96 56.0 65 65 35 4.54 0.5354
WVFGRD96 57.0 65 65 35 4.54 0.5402
WVFGRD96 58.0 65 65 35 4.55 0.5459
WVFGRD96 59.0 65 65 35 4.55 0.5508
WVFGRD96 60.0 65 65 35 4.56 0.5551
WVFGRD96 61.0 65 65 35 4.56 0.5600
WVFGRD96 62.0 65 65 35 4.57 0.5645
WVFGRD96 63.0 65 65 35 4.57 0.5682
WVFGRD96 64.0 65 65 35 4.58 0.5726
WVFGRD96 65.0 70 60 40 4.58 0.5757
WVFGRD96 66.0 65 65 35 4.58 0.5797
WVFGRD96 67.0 65 65 40 4.59 0.5831
WVFGRD96 68.0 65 65 40 4.59 0.5854
WVFGRD96 69.0 65 65 40 4.60 0.5890
WVFGRD96 70.0 65 65 40 4.60 0.5915
WVFGRD96 71.0 65 65 40 4.60 0.5944
WVFGRD96 72.0 65 65 40 4.61 0.5962
WVFGRD96 73.0 65 65 40 4.61 0.5986
WVFGRD96 74.0 65 65 40 4.61 0.6004
WVFGRD96 75.0 65 65 40 4.62 0.6024
WVFGRD96 76.0 65 65 40 4.62 0.6036
WVFGRD96 77.0 65 65 40 4.62 0.6049
WVFGRD96 78.0 65 65 40 4.63 0.6065
WVFGRD96 79.0 65 65 40 4.63 0.6073
WVFGRD96 80.0 65 65 40 4.63 0.6081
WVFGRD96 81.0 65 65 40 4.64 0.6089
WVFGRD96 82.0 65 65 40 4.64 0.6097
WVFGRD96 83.0 65 65 40 4.64 0.6106
WVFGRD96 84.0 65 65 40 4.65 0.6103
WVFGRD96 85.0 65 65 40 4.65 0.6114
WVFGRD96 86.0 65 65 40 4.65 0.6110
WVFGRD96 87.0 65 65 40 4.65 0.6120
WVFGRD96 88.0 65 65 40 4.66 0.6113
WVFGRD96 89.0 65 65 40 4.66 0.6116
WVFGRD96 90.0 65 65 40 4.66 0.6116
WVFGRD96 91.0 65 65 40 4.67 0.6113
WVFGRD96 92.0 65 65 40 4.67 0.6109
WVFGRD96 93.0 65 65 40 4.67 0.6096
WVFGRD96 94.0 65 65 40 4.67 0.6102
WVFGRD96 95.0 65 65 40 4.68 0.6091
WVFGRD96 96.0 65 65 40 4.68 0.6085
WVFGRD96 97.0 65 65 40 4.68 0.6074
WVFGRD96 98.0 65 65 40 4.68 0.6062
WVFGRD96 99.0 65 65 40 4.69 0.6060
WVFGRD96 100.0 65 65 40 4.69 0.6046
WVFGRD96 101.0 65 65 40 4.69 0.6032
WVFGRD96 102.0 65 65 40 4.69 0.6021
WVFGRD96 103.0 65 65 40 4.70 0.6006
WVFGRD96 104.0 65 65 40 4.70 0.5994
WVFGRD96 105.0 65 65 40 4.70 0.5982
WVFGRD96 106.0 65 65 40 4.70 0.5954
WVFGRD96 107.0 65 65 40 4.70 0.5948
WVFGRD96 108.0 65 65 40 4.71 0.5932
WVFGRD96 109.0 65 65 40 4.71 0.5910
WVFGRD96 110.0 65 65 40 4.71 0.5897
WVFGRD96 111.0 65 65 40 4.71 0.5871
WVFGRD96 112.0 65 65 40 4.71 0.5854
WVFGRD96 113.0 65 65 40 4.72 0.5836
WVFGRD96 114.0 65 65 40 4.72 0.5814
WVFGRD96 115.0 65 65 40 4.72 0.5788
WVFGRD96 116.0 65 65 40 4.72 0.5770
WVFGRD96 117.0 65 65 40 4.72 0.5747
WVFGRD96 118.0 65 60 40 4.71 0.5726
WVFGRD96 119.0 65 60 40 4.72 0.5715
WVFGRD96 120.0 65 60 40 4.72 0.5690
WVFGRD96 121.0 65 60 40 4.72 0.5666
WVFGRD96 122.0 65 60 40 4.72 0.5653
WVFGRD96 123.0 65 60 40 4.72 0.5630
WVFGRD96 124.0 65 60 40 4.73 0.5604
WVFGRD96 125.0 65 60 40 4.73 0.5588
WVFGRD96 126.0 65 60 40 4.73 0.5562
WVFGRD96 127.0 65 60 40 4.73 0.5537
WVFGRD96 128.0 65 60 40 4.73 0.5513
WVFGRD96 129.0 65 60 40 4.73 0.5496
The best solution is
WVFGRD96 87.0 65 65 40 4.65 0.6120
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 0.06 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: