2011/08/08 16:00:48 58.212 -151.511 45 4.30 Alaska
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2011/08/08 16:00:48:0 58.21 -151.51 45.0 4.3 Alaska
Stations used:
AK.BMR AK.BRLK AK.CAST AK.CNP AK.DIV AK.EYAK AK.FID AK.GHO
AK.HOM AK.KNK AK.KTH AK.PPLA AK.RC01 AK.RND AK.SAW AK.SCM
AK.SSN AK.SWD AK.TRF AT.OHAK AT.PMR AT.SVW2 II.KDAK
Filtering commands used:
hp c 0.02 n 3
lp c 0.06 n 3
Best Fitting Double Couple
Mo = 5.01e+22 dyne-cm
Mw = 4.40
Z = 40 km
Plane Strike Dip Rake
NP1 10 60 -125
NP2 245 45 -45
Principal Axes:
Axis Value Plunge Azimuth
T 5.01e+22 8 125
N 0.00e+00 30 30
P -5.01e+22 59 229
Moment Tensor: (dyne-cm)
Component Value
Mxx 9.91e+21
Mxy -2.97e+22
Mxz 1.06e+22
Myy 2.55e+22
Myz 2.27e+22
Mzz -3.54e+22
###########---
#################-----
####################--------
######################--------
#################-------#####-----
#############-------------#########-
###########----------------###########
#########-------------------############
#######---------------------############
#######----------------------#############
#####------------------------#############
####-------------------------#############
###----------- -----------##############
##----------- P -----------#############
#------------ ----------##############
-------------------------######### #
-----------------------########## T
---------------------###########
------------------############
---------------#############
-----------###########
-----#########
Global CMT Convention Moment Tensor:
R T P
-3.54e+22 1.06e+22 -2.27e+22
1.06e+22 9.91e+21 2.97e+22
-2.27e+22 2.97e+22 2.55e+22
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20110808160048/index.html
|
STK = 245
DIP = 45
RAKE = -45
MW = 4.40
HS = 40.0
The NDK file is 20110808160048.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2011/08/08 16:00:48:0 58.21 -151.51 45.0 4.3 Alaska
Stations used:
AK.BMR AK.BRLK AK.CAST AK.CNP AK.DIV AK.EYAK AK.FID AK.GHO
AK.HOM AK.KNK AK.KTH AK.PPLA AK.RC01 AK.RND AK.SAW AK.SCM
AK.SSN AK.SWD AK.TRF AT.OHAK AT.PMR AT.SVW2 II.KDAK
Filtering commands used:
hp c 0.02 n 3
lp c 0.06 n 3
Best Fitting Double Couple
Mo = 5.01e+22 dyne-cm
Mw = 4.40
Z = 40 km
Plane Strike Dip Rake
NP1 10 60 -125
NP2 245 45 -45
Principal Axes:
Axis Value Plunge Azimuth
T 5.01e+22 8 125
N 0.00e+00 30 30
P -5.01e+22 59 229
Moment Tensor: (dyne-cm)
Component Value
Mxx 9.91e+21
Mxy -2.97e+22
Mxz 1.06e+22
Myy 2.55e+22
Myz 2.27e+22
Mzz -3.54e+22
###########---
#################-----
####################--------
######################--------
#################-------#####-----
#############-------------#########-
###########----------------###########
#########-------------------############
#######---------------------############
#######----------------------#############
#####------------------------#############
####-------------------------#############
###----------- -----------##############
##----------- P -----------#############
#------------ ----------##############
-------------------------######### #
-----------------------########## T
---------------------###########
------------------############
---------------#############
-----------###########
-----#########
Global CMT Convention Moment Tensor:
R T P
-3.54e+22 1.06e+22 -2.27e+22
1.06e+22 9.91e+21 2.97e+22
-2.27e+22 2.97e+22 2.55e+22
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20110808160048/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 0.5 215 45 90 3.76 0.2382
WVFGRD96 1.0 300 45 90 3.63 0.2482
WVFGRD96 2.0 120 45 90 3.73 0.3156
WVFGRD96 3.0 305 45 95 3.82 0.3525
WVFGRD96 4.0 100 50 60 3.85 0.3310
WVFGRD96 5.0 85 65 35 3.83 0.3028
WVFGRD96 6.0 80 90 -30 3.83 0.2932
WVFGRD96 7.0 260 90 30 3.85 0.3013
WVFGRD96 8.0 260 90 35 3.89 0.3114
WVFGRD96 9.0 260 90 40 3.90 0.3196
WVFGRD96 10.0 75 80 -35 3.92 0.3342
WVFGRD96 11.0 245 60 -35 3.95 0.3528
WVFGRD96 12.0 245 60 -35 3.96 0.3740
WVFGRD96 13.0 245 60 -40 3.98 0.3948
WVFGRD96 14.0 245 60 -40 4.00 0.4144
WVFGRD96 15.0 245 55 -40 4.01 0.4335
WVFGRD96 16.0 245 55 -40 4.03 0.4514
WVFGRD96 17.0 245 55 -40 4.04 0.4684
WVFGRD96 18.0 245 55 -40 4.05 0.4839
WVFGRD96 19.0 245 55 -40 4.06 0.4981
WVFGRD96 20.0 245 55 -40 4.08 0.5114
WVFGRD96 21.0 245 55 -40 4.10 0.5226
WVFGRD96 22.0 245 55 -40 4.11 0.5345
WVFGRD96 23.0 245 55 -45 4.12 0.5458
WVFGRD96 24.0 245 55 -45 4.13 0.5564
WVFGRD96 25.0 245 55 -45 4.14 0.5661
WVFGRD96 26.0 245 55 -45 4.15 0.5750
WVFGRD96 27.0 245 55 -45 4.16 0.5829
WVFGRD96 28.0 245 55 -45 4.17 0.5902
WVFGRD96 29.0 245 55 -45 4.19 0.5964
WVFGRD96 30.0 245 50 -45 4.20 0.6018
WVFGRD96 31.0 245 50 -45 4.21 0.6064
WVFGRD96 32.0 245 50 -45 4.22 0.6096
WVFGRD96 33.0 250 55 -40 4.22 0.6114
WVFGRD96 34.0 250 55 -40 4.23 0.6128
WVFGRD96 35.0 250 55 -40 4.24 0.6128
WVFGRD96 36.0 250 50 -40 4.25 0.6118
WVFGRD96 37.0 250 50 -40 4.26 0.6094
WVFGRD96 38.0 250 55 -40 4.26 0.6052
WVFGRD96 39.0 250 55 -40 4.26 0.5996
WVFGRD96 40.0 245 45 -45 4.40 0.6174
WVFGRD96 41.0 245 45 -45 4.40 0.6160
WVFGRD96 42.0 245 45 -50 4.42 0.6131
WVFGRD96 43.0 245 40 -50 4.43 0.6102
WVFGRD96 44.0 245 40 -50 4.44 0.6068
WVFGRD96 45.0 245 40 -50 4.45 0.6021
WVFGRD96 46.0 245 40 -50 4.45 0.5962
WVFGRD96 47.0 245 40 -50 4.46 0.5894
WVFGRD96 48.0 245 40 -50 4.47 0.5818
WVFGRD96 49.0 245 40 -50 4.47 0.5735
WVFGRD96 50.0 245 35 -50 4.48 0.5654
WVFGRD96 51.0 250 35 -45 4.49 0.5566
WVFGRD96 52.0 250 35 -45 4.49 0.5480
WVFGRD96 53.0 250 35 -45 4.49 0.5397
WVFGRD96 54.0 250 35 -45 4.50 0.5306
WVFGRD96 55.0 250 35 -45 4.50 0.5208
WVFGRD96 56.0 250 35 -45 4.50 0.5104
WVFGRD96 57.0 255 35 -40 4.50 0.5007
WVFGRD96 58.0 255 35 -40 4.51 0.4916
WVFGRD96 59.0 255 35 -40 4.51 0.4817
WVFGRD96 60.0 255 35 -40 4.51 0.4719
WVFGRD96 61.0 255 35 -40 4.51 0.4620
WVFGRD96 62.0 255 35 -40 4.51 0.4514
WVFGRD96 63.0 260 35 -35 4.51 0.4425
WVFGRD96 64.0 260 35 -35 4.51 0.4334
WVFGRD96 65.0 260 35 -35 4.51 0.4244
WVFGRD96 66.0 250 55 -30 4.46 0.4185
WVFGRD96 67.0 250 55 -30 4.46 0.4137
WVFGRD96 68.0 250 55 -30 4.46 0.4087
WVFGRD96 69.0 250 55 -30 4.46 0.4047
WVFGRD96 70.0 250 55 -30 4.47 0.4002
WVFGRD96 71.0 250 55 -30 4.47 0.3960
WVFGRD96 72.0 250 55 -30 4.47 0.3913
WVFGRD96 73.0 255 60 -25 4.46 0.3877
WVFGRD96 74.0 255 60 -25 4.46 0.3840
WVFGRD96 75.0 255 65 -25 4.46 0.3804
WVFGRD96 76.0 255 65 -25 4.46 0.3767
WVFGRD96 77.0 255 65 -25 4.46 0.3734
WVFGRD96 78.0 255 65 -25 4.46 0.3696
WVFGRD96 79.0 255 70 -25 4.46 0.3664
WVFGRD96 80.0 255 70 -25 4.46 0.3630
WVFGRD96 81.0 255 75 -25 4.47 0.3603
WVFGRD96 82.0 255 75 -25 4.47 0.3575
WVFGRD96 83.0 255 75 -25 4.47 0.3548
WVFGRD96 84.0 255 75 -25 4.47 0.3519
WVFGRD96 85.0 255 75 -25 4.47 0.3494
WVFGRD96 86.0 255 75 -25 4.47 0.3466
WVFGRD96 87.0 255 85 -25 4.48 0.3441
WVFGRD96 88.0 260 45 15 4.38 0.3370
WVFGRD96 89.0 260 45 15 4.38 0.3361
WVFGRD96 90.0 260 45 15 4.39 0.3349
WVFGRD96 91.0 260 45 15 4.39 0.3332
WVFGRD96 92.0 260 45 15 4.39 0.3324
WVFGRD96 93.0 260 45 15 4.39 0.3311
WVFGRD96 94.0 260 45 15 4.39 0.3302
WVFGRD96 95.0 260 45 20 4.39 0.3298
WVFGRD96 96.0 265 40 25 4.39 0.3282
WVFGRD96 97.0 265 40 25 4.39 0.3276
WVFGRD96 98.0 265 40 25 4.39 0.3268
WVFGRD96 99.0 265 40 25 4.39 0.3261
WVFGRD96 100.0 265 40 25 4.39 0.3247
WVFGRD96 101.0 265 40 25 4.39 0.3237
WVFGRD96 102.0 235 45 -50 4.49 0.3260
WVFGRD96 103.0 235 45 -50 4.49 0.3250
WVFGRD96 104.0 235 45 -50 4.49 0.3258
WVFGRD96 105.0 235 45 -50 4.49 0.3248
WVFGRD96 106.0 235 45 -50 4.49 0.3253
WVFGRD96 107.0 235 40 -55 4.48 0.3267
WVFGRD96 108.0 235 40 -55 4.48 0.3266
WVFGRD96 109.0 235 40 -55 4.48 0.3283
WVFGRD96 110.0 235 40 -55 4.48 0.3288
WVFGRD96 111.0 235 40 -55 4.48 0.3308
WVFGRD96 112.0 235 40 -55 4.48 0.3318
WVFGRD96 113.0 235 40 -55 4.48 0.3320
WVFGRD96 114.0 235 40 -55 4.48 0.3334
WVFGRD96 115.0 235 40 -55 4.48 0.3343
WVFGRD96 116.0 235 40 -50 4.48 0.3345
WVFGRD96 117.0 235 40 -50 4.48 0.3353
WVFGRD96 118.0 235 40 -50 4.48 0.3354
WVFGRD96 119.0 235 40 -50 4.49 0.3363
WVFGRD96 120.0 235 40 -50 4.49 0.3362
WVFGRD96 121.0 235 40 -50 4.49 0.3369
WVFGRD96 122.0 235 40 -50 4.49 0.3375
WVFGRD96 123.0 235 40 -50 4.49 0.3371
WVFGRD96 124.0 235 40 -50 4.49 0.3373
WVFGRD96 125.0 235 40 -50 4.49 0.3372
WVFGRD96 126.0 235 40 -50 4.49 0.3372
WVFGRD96 127.0 230 35 -65 4.47 0.3372
WVFGRD96 128.0 230 35 -65 4.47 0.3376
WVFGRD96 129.0 230 35 -65 4.47 0.3379
The best solution is
WVFGRD96 40.0 245 45 -45 4.40 0.6174
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: