2011/07/21 06:20:11 60.042 -152.853 94 4.10 Alaska
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2011/07/21 06:20:11:0 60.04 -152.85 94.0 4.1 Alaska
Stations used:
AK.CNP AK.GHO AK.HOM AK.SAW AK.SSN AK.SWD AT.PMR AT.SVW2
II.KDAK
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 3.43e+22 dyne-cm
Mw = 4.29
Z = 112 km
Plane Strike Dip Rake
NP1 55 70 50
NP2 303 44 150
Principal Axes:
Axis Value Plunge Azimuth
T 3.43e+22 49 282
N 0.00e+00 37 71
P -3.43e+22 15 173
Moment Tensor: (dyne-cm)
Component Value
Mxx -3.08e+22
Mxy 8.49e+20
Mxz 1.22e+22
Myy 1.39e+22
Myz -1.77e+22
Mzz 1.69e+22
--------------
----------------------
----------------------------
------##----------------------
-##################---------------
#######################-----------##
###########################-------####
##############################----######
######## #####################-#######
######### T ####################--########
######### ##################------######
############################---------#####
##########################-----------#####
######################---------------###
###################------------------###
###############----------------------#
##########--------------------------
----------------------------------
------------------------------
--------------- ----------
------------ P -------
-------- ---
Global CMT Convention Moment Tensor:
R T P
1.69e+22 1.22e+22 1.77e+22
1.22e+22 -3.08e+22 -8.49e+20
1.77e+22 -8.49e+20 1.39e+22
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20110721062011/index.html
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STK = 55
DIP = 70
RAKE = 50
MW = 4.29
HS = 112.0
The NDK file is 20110721062011.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2011/07/21 06:20:11:0 60.04 -152.85 94.0 4.1 Alaska
Stations used:
AK.CNP AK.GHO AK.HOM AK.SAW AK.SSN AK.SWD AT.PMR AT.SVW2
II.KDAK
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 3.43e+22 dyne-cm
Mw = 4.29
Z = 112 km
Plane Strike Dip Rake
NP1 55 70 50
NP2 303 44 150
Principal Axes:
Axis Value Plunge Azimuth
T 3.43e+22 49 282
N 0.00e+00 37 71
P -3.43e+22 15 173
Moment Tensor: (dyne-cm)
Component Value
Mxx -3.08e+22
Mxy 8.49e+20
Mxz 1.22e+22
Myy 1.39e+22
Myz -1.77e+22
Mzz 1.69e+22
--------------
----------------------
----------------------------
------##----------------------
-##################---------------
#######################-----------##
###########################-------####
##############################----######
######## #####################-#######
######### T ####################--########
######### ##################------######
############################---------#####
##########################-----------#####
######################---------------###
###################------------------###
###############----------------------#
##########--------------------------
----------------------------------
------------------------------
--------------- ----------
------------ P -------
-------- ---
Global CMT Convention Moment Tensor:
R T P
1.69e+22 1.22e+22 1.77e+22
1.22e+22 -3.08e+22 -8.49e+20
1.77e+22 -8.49e+20 1.39e+22
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20110721062011/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 0.10 n 3The results of this grid search from 0.5 to 19 km depth are as follow:
DEPTH STK DIP RAKE MW FIT
WVFGRD96 50.0 55 65 5 4.10 0.3193
WVFGRD96 51.0 55 60 5 4.11 0.3226
WVFGRD96 52.0 55 60 5 4.12 0.3258
WVFGRD96 53.0 60 70 10 4.14 0.3296
WVFGRD96 54.0 225 75 -30 4.12 0.3368
WVFGRD96 55.0 225 75 -30 4.13 0.3435
WVFGRD96 56.0 225 75 -30 4.14 0.3496
WVFGRD96 57.0 230 80 -30 4.16 0.3550
WVFGRD96 58.0 230 80 -30 4.16 0.3600
WVFGRD96 59.0 230 80 -30 4.17 0.3641
WVFGRD96 60.0 230 80 -30 4.18 0.3701
WVFGRD96 61.0 230 80 -30 4.18 0.3747
WVFGRD96 62.0 230 80 -30 4.19 0.3776
WVFGRD96 63.0 230 80 -30 4.19 0.3798
WVFGRD96 64.0 230 85 -30 4.19 0.3837
WVFGRD96 65.0 230 85 -30 4.19 0.3881
WVFGRD96 66.0 230 85 -30 4.20 0.3909
WVFGRD96 67.0 60 80 25 4.21 0.3925
WVFGRD96 68.0 60 80 25 4.21 0.3992
WVFGRD96 69.0 60 80 25 4.22 0.4043
WVFGRD96 70.0 60 75 35 4.20 0.4109
WVFGRD96 71.0 60 75 35 4.20 0.4196
WVFGRD96 72.0 60 70 35 4.19 0.4273
WVFGRD96 73.0 60 70 35 4.19 0.4331
WVFGRD96 74.0 60 70 35 4.20 0.4423
WVFGRD96 75.0 60 70 35 4.20 0.4492
WVFGRD96 76.0 60 70 35 4.21 0.4544
WVFGRD96 77.0 60 70 35 4.21 0.4630
WVFGRD96 78.0 60 70 40 4.21 0.4686
WVFGRD96 79.0 60 70 40 4.21 0.4755
WVFGRD96 80.0 60 70 40 4.22 0.4826
WVFGRD96 81.0 60 70 40 4.22 0.4873
WVFGRD96 82.0 60 70 40 4.23 0.4948
WVFGRD96 83.0 60 70 40 4.23 0.4996
WVFGRD96 84.0 60 70 40 4.23 0.5056
WVFGRD96 85.0 60 70 40 4.24 0.5114
WVFGRD96 86.0 60 70 40 4.24 0.5152
WVFGRD96 87.0 60 70 40 4.24 0.5218
WVFGRD96 88.0 60 70 40 4.24 0.5249
WVFGRD96 89.0 60 70 40 4.25 0.5310
WVFGRD96 90.0 60 65 40 4.23 0.5329
WVFGRD96 91.0 60 70 40 4.25 0.5398
WVFGRD96 92.0 60 65 40 4.24 0.5420
WVFGRD96 93.0 60 65 45 4.23 0.5483
WVFGRD96 94.0 60 65 45 4.24 0.5511
WVFGRD96 95.0 60 65 45 4.24 0.5575
WVFGRD96 96.0 60 65 45 4.24 0.5592
WVFGRD96 97.0 60 65 45 4.25 0.5652
WVFGRD96 98.0 60 65 45 4.25 0.5670
WVFGRD96 99.0 60 65 45 4.25 0.5716
WVFGRD96 100.0 60 65 45 4.25 0.5731
WVFGRD96 101.0 60 65 45 4.26 0.5780
WVFGRD96 102.0 60 65 45 4.26 0.5778
WVFGRD96 103.0 60 65 45 4.26 0.5830
WVFGRD96 104.0 60 65 45 4.26 0.5829
WVFGRD96 105.0 60 65 45 4.27 0.5860
WVFGRD96 106.0 60 65 45 4.27 0.5867
WVFGRD96 107.0 60 65 45 4.27 0.5881
WVFGRD96 108.0 60 65 45 4.27 0.5889
WVFGRD96 109.0 60 65 45 4.27 0.5892
WVFGRD96 110.0 60 65 45 4.28 0.5897
WVFGRD96 111.0 60 65 45 4.28 0.5883
WVFGRD96 112.0 55 70 50 4.29 0.5904
WVFGRD96 113.0 55 70 50 4.29 0.5887
WVFGRD96 114.0 55 70 50 4.29 0.5897
WVFGRD96 115.0 55 70 50 4.30 0.5887
WVFGRD96 116.0 55 70 50 4.30 0.5875
WVFGRD96 117.0 55 70 50 4.30 0.5865
WVFGRD96 118.0 55 70 50 4.30 0.5841
WVFGRD96 119.0 55 70 50 4.30 0.5831
WVFGRD96 120.0 55 70 50 4.31 0.5816
WVFGRD96 121.0 55 70 50 4.31 0.5792
WVFGRD96 122.0 50 70 50 4.30 0.5770
WVFGRD96 123.0 55 70 50 4.31 0.5733
WVFGRD96 124.0 50 70 50 4.30 0.5726
WVFGRD96 125.0 50 70 50 4.30 0.5700
WVFGRD96 126.0 50 70 50 4.30 0.5666
WVFGRD96 127.0 50 70 50 4.30 0.5653
WVFGRD96 128.0 50 70 50 4.31 0.5605
WVFGRD96 129.0 50 70 50 4.31 0.5592
The best solution is
WVFGRD96 112.0 55 70 50 4.29 0.5904
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
hp c 0.02 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: