2008/11/03 13:14:13 42.7820 -105.1210 5.0 4.10 Wyoming
USGS Felt map for this earthquake
SLU Moment Tensor Solution
2008/11/03 13:14:13 42.7820 -105.1210 5.0 4.10 Wyoming
Best Fitting Double Couple
Mo = 2.57e+21 dyne-cm
Mw = 3.54
Z = 18 km
Plane Strike Dip Rake
NP1 60 73 -121
NP2 305 35 -30
Principal Axes:
Axis Value Plunge Azimuth
T 2.57e+21 22 174
N 0.00e+00 30 70
P -2.57e+21 51 294
Moment Tensor: (dyne-cm)
Component Value
Mxx 2.01e+21
Mxy 1.31e+20
Mxz -1.41e+21
Myy -8.02e+20
Myz 1.24e+21
Mzz -1.21e+21
##############
######################
############################
#-----------------############
-----------------------###########
---------------------------#########
------------------------------######--
---------- --------------------##-----
---------- P --------------------#------
----------- ------------------####------
------------------------------#######-----
----------------------------##########----
-------------------------#############----
--------------------##################--
-----------------#####################--
-----------##########################-
--#################################-
##################################
############### ############
############## T ###########
########### ########
##############
Harvard Convention
Moment Tensor:
R T F
-1.21e+21 -1.41e+21 -1.24e+21
-1.41e+21 2.01e+21 -1.31e+20
-1.24e+21 -1.31e+20 -8.02e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20081103131413/index.html
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STK = 305
DIP = 35
RAKE = -30
MW = 3.54
HS = 18.0
The waveform inversion is preferred.
The following compares this source inversion to others
SLU Moment Tensor Solution
2008/11/03 13:14:13 42.7820 -105.1210 5.0 4.10 Wyoming
Best Fitting Double Couple
Mo = 2.57e+21 dyne-cm
Mw = 3.54
Z = 18 km
Plane Strike Dip Rake
NP1 60 73 -121
NP2 305 35 -30
Principal Axes:
Axis Value Plunge Azimuth
T 2.57e+21 22 174
N 0.00e+00 30 70
P -2.57e+21 51 294
Moment Tensor: (dyne-cm)
Component Value
Mxx 2.01e+21
Mxy 1.31e+20
Mxz -1.41e+21
Myy -8.02e+20
Myz 1.24e+21
Mzz -1.21e+21
##############
######################
############################
#-----------------############
-----------------------###########
---------------------------#########
------------------------------######--
---------- --------------------##-----
---------- P --------------------#------
----------- ------------------####------
------------------------------#######-----
----------------------------##########----
-------------------------#############----
--------------------##################--
-----------------#####################--
-----------##########################-
--#################################-
##################################
############### ############
############## T ###########
########### ########
##############
Harvard Convention
Moment Tensor:
R T F
-1.21e+21 -1.41e+21 -1.24e+21
-1.41e+21 2.01e+21 -1.31e+20
-1.24e+21 -1.31e+20 -8.02e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20081103131413/index.html
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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 3 br c 0.12 0.25 n 4 p 2The results of this grid search from 0.5 to 19 km depth are as follow:
DEPTH STK DIP RAKE MW FIT
WVFGRD96 0.5 225 45 90 3.35 0.3452
WVFGRD96 1.0 225 45 90 3.40 0.3571
WVFGRD96 2.0 250 45 90 3.45 0.3381
WVFGRD96 3.0 335 30 25 3.48 0.3091
WVFGRD96 4.0 335 30 25 3.48 0.3438
WVFGRD96 5.0 330 30 15 3.47 0.3708
WVFGRD96 6.0 330 30 15 3.46 0.3904
WVFGRD96 7.0 325 35 5 3.46 0.4047
WVFGRD96 8.0 315 35 -20 3.46 0.4177
WVFGRD96 9.0 315 35 -20 3.46 0.4292
WVFGRD96 10.0 315 35 -20 3.49 0.4372
WVFGRD96 11.0 310 35 -25 3.50 0.4459
WVFGRD96 12.0 310 35 -30 3.50 0.4522
WVFGRD96 13.0 310 35 -30 3.51 0.4577
WVFGRD96 14.0 310 35 -25 3.51 0.4619
WVFGRD96 15.0 310 35 -25 3.52 0.4650
WVFGRD96 16.0 305 35 -30 3.53 0.4673
WVFGRD96 17.0 310 35 -25 3.53 0.4688
WVFGRD96 18.0 305 35 -30 3.54 0.4693
WVFGRD96 19.0 305 35 -30 3.55 0.4690
WVFGRD96 20.0 305 35 -30 3.58 0.4677
WVFGRD96 21.0 310 35 -25 3.59 0.4656
WVFGRD96 22.0 310 35 -25 3.60 0.4626
WVFGRD96 23.0 310 35 -25 3.60 0.4583
WVFGRD96 24.0 310 35 -25 3.61 0.4533
WVFGRD96 25.0 310 35 -25 3.62 0.4479
WVFGRD96 26.0 310 30 -25 3.63 0.4418
WVFGRD96 27.0 310 30 -20 3.64 0.4350
WVFGRD96 28.0 310 30 -20 3.64 0.4273
WVFGRD96 29.0 310 30 -20 3.65 0.4186
WVFGRD96 30.0 310 30 -20 3.66 0.4092
WVFGRD96 31.0 310 30 -20 3.67 0.3996
WVFGRD96 32.0 310 30 -20 3.67 0.3891
WVFGRD96 33.0 310 35 -20 3.68 0.3785
WVFGRD96 34.0 310 35 -20 3.69 0.3675
WVFGRD96 35.0 310 35 -25 3.69 0.3564
WVFGRD96 36.0 310 35 -20 3.69 0.3452
WVFGRD96 37.0 310 35 -20 3.70 0.3346
WVFGRD96 38.0 340 30 25 3.70 0.3262
WVFGRD96 39.0 340 30 25 3.70 0.3199
WVFGRD96 40.0 340 20 20 3.82 0.3121
WVFGRD96 41.0 340 25 25 3.83 0.3016
WVFGRD96 42.0 250 75 65 3.80 0.2933
WVFGRD96 43.0 250 75 65 3.81 0.2866
WVFGRD96 44.0 250 75 60 3.81 0.2800
WVFGRD96 45.0 250 75 60 3.81 0.2734
WVFGRD96 46.0 215 65 -65 3.86 0.2689
WVFGRD96 47.0 215 65 -65 3.87 0.2669
WVFGRD96 48.0 215 65 -60 3.87 0.2647
WVFGRD96 49.0 215 65 -60 3.88 0.2631
WVFGRD96 50.0 215 65 -60 3.88 0.2612
The best solution is
WVFGRD96 18.0 305 35 -30 3.54 0.4693
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 componnet is plotted to the same scale and peak amplitudes are indicated by the numbers to the left of each trace. The number in black at the rightr of each predicted traces 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 bandpass filter used in the processing and for the display was
hp c 0.02 n 3 lp c 0.10 n 3 br c 0.12 0.25 n 4 p 2
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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. |
Should the national backbone of the USGS Advanced National Seismic System (ANSS) be implemented with an interstation separation of 300 km, it is very likely that an earthquake such as this would have been recorded at distances on the order of 100-200 km. This means that the closest station would have information on source depth and mechanism that was lacking here.
Dr. Harley Benz, USGS, provided the USGS USNSN digital data. The digital data used in this study were provided by Natural Resources Canada through their AUTODRM site http://www.seismo.nrcan.gc.ca/nwfa/autodrm/autodrm_req_e.php, and IRIS using their BUD interface.
Thanks also to the many seismic network operators whose dedication make this effort possible: University of Alaska, University of Washington, Oregon State University, University of Utah, Montana Bureas of Mines, UC Berkely, Caltech, UC San Diego, Saint L ouis University, Universityof Memphis, Lamont Doehrty Earth Observatory, Boston College, the Iris stations and the Transportable Array of EarthScope.
The CUS used for the waveform synthetic seismograms and for the surface wave eigenfunctions and dispersion is as follows:
MODEL.01 CUS Model with Q from simple gamma values 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 1.0000 5.0000 2.8900 2.5000 0.172E-02 0.387E-02 0.00 0.00 1.00 1.00 9.0000 6.1000 3.5200 2.7300 0.160E-02 0.363E-02 0.00 0.00 1.00 1.00 10.0000 6.4000 3.7000 2.8200 0.149E-02 0.336E-02 0.00 0.00 1.00 1.00 20.0000 6.7000 3.8700 2.9020 0.000E-04 0.000E-04 0.00 0.00 1.00 1.00 0.0000 8.1500 4.7000 3.3640 0.194E-02 0.431E-02 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:
DATE=Mon Nov 3 11:12:53 CST 2008