USGS/SLU Moment Tensor Solution
ENS 2017/11/03 23:11:11:0 43.53 -107.43 5.0 4.2 Wyoming
Stations used:
IU.RSSD IW.FLWY IW.FXWY IW.IMW IW.LOHW IW.MOOW IW.PHWY
IW.RWWY IW.SNOW IW.TPAW TA.K22A TA.N23A US.AHID US.BW06
US.HWUT US.ISCO US.LAO US.LKWY US.RLMT WY.YMP
Filtering commands used:
cut o DIST/3.3 -20 o DIST/3.3 +40
rtr
taper w 0.1
hp c 0.03 n 3
lp c 0.08 n 3
Best Fitting Double Couple
Mo = 1.45e+22 dyne-cm
Mw = 4.04
Z = 20 km
Plane Strike Dip Rake
NP1 290 50 -85
NP2 102 40 -96
Principal Axes:
Axis Value Plunge Azimuth
T 1.45e+22 5 16
N 0.00e+00 4 107
P -1.45e+22 84 235
Moment Tensor: (dyne-cm)
Component Value
Mxx 1.31e+22
Mxy 3.82e+21
Mxz 2.07e+21
Myy 1.04e+21
Myz 1.62e+21
Mzz -1.42e+22
########### T
############### ####
############################
##############################
##################################
####---------------#################
#------------------------#############
-----------------------------###########
--------------------------------########
#----------------------------------#######
##---------------- ----------------#####
###--------------- P -----------------####
####-------------- ------------------###
####-----------------------------------#
######----------------------------------
########----------------------------##
##########----------------------####
##############------------########
##############################
############################
######################
##############
Global CMT Convention Moment Tensor:
R T P
-1.42e+22 2.07e+21 -1.62e+21
2.07e+21 1.31e+22 -3.82e+21
-1.62e+21 -3.82e+21 1.04e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20171103231111/index.html
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STK = 290
DIP = 50
RAKE = -85
MW = 4.04
HS = 20.0
The NDK file is 20171103231111.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2017/11/03 23:11:11:0 43.53 -107.43 5.0 4.2 Wyoming
Stations used:
IU.RSSD IW.FLWY IW.FXWY IW.IMW IW.LOHW IW.MOOW IW.PHWY
IW.RWWY IW.SNOW IW.TPAW TA.K22A TA.N23A US.AHID US.BW06
US.HWUT US.ISCO US.LAO US.LKWY US.RLMT WY.YMP
Filtering commands used:
cut o DIST/3.3 -20 o DIST/3.3 +40
rtr
taper w 0.1
hp c 0.03 n 3
lp c 0.08 n 3
Best Fitting Double Couple
Mo = 1.45e+22 dyne-cm
Mw = 4.04
Z = 20 km
Plane Strike Dip Rake
NP1 290 50 -85
NP2 102 40 -96
Principal Axes:
Axis Value Plunge Azimuth
T 1.45e+22 5 16
N 0.00e+00 4 107
P -1.45e+22 84 235
Moment Tensor: (dyne-cm)
Component Value
Mxx 1.31e+22
Mxy 3.82e+21
Mxz 2.07e+21
Myy 1.04e+21
Myz 1.62e+21
Mzz -1.42e+22
########### T
############### ####
############################
##############################
##################################
####---------------#################
#------------------------#############
-----------------------------###########
--------------------------------########
#----------------------------------#######
##---------------- ----------------#####
###--------------- P -----------------####
####-------------- ------------------###
####-----------------------------------#
######----------------------------------
########----------------------------##
##########----------------------####
##############------------########
##############################
############################
######################
##############
Global CMT Convention Moment Tensor:
R T P
-1.42e+22 2.07e+21 -1.62e+21
2.07e+21 1.31e+22 -3.82e+21
-1.62e+21 -3.82e+21 1.04e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20171103231111/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:
cut o DIST/3.3 -20 o DIST/3.3 +40 rtr taper w 0.1 hp c 0.03 n 3 lp c 0.08 n 3The results of this grid search from 0.5 to 19 km depth are as follow:
DEPTH STK DIP RAKE MW FIT
WVFGRD96 1.0 35 45 95 3.75 0.4563
WVFGRD96 2.0 30 45 85 3.85 0.4725
WVFGRD96 3.0 50 50 60 3.94 0.4163
WVFGRD96 4.0 210 85 -35 3.84 0.3888
WVFGRD96 5.0 210 85 -40 3.83 0.3919
WVFGRD96 6.0 335 55 -30 3.84 0.4059
WVFGRD96 7.0 330 45 -30 3.85 0.4278
WVFGRD96 8.0 330 45 -35 3.87 0.4511
WVFGRD96 9.0 325 45 -45 3.89 0.4734
WVFGRD96 10.0 315 40 -60 3.94 0.4941
WVFGRD96 11.0 110 35 -85 3.97 0.5233
WVFGRD96 12.0 110 40 -90 3.97 0.5462
WVFGRD96 13.0 110 40 -90 3.98 0.5638
WVFGRD96 14.0 105 40 -90 3.98 0.5768
WVFGRD96 15.0 105 40 -90 3.99 0.5862
WVFGRD96 16.0 105 40 -90 3.99 0.5926
WVFGRD96 17.0 290 50 -85 4.00 0.5971
WVFGRD96 18.0 290 50 -85 4.01 0.5988
WVFGRD96 19.0 290 50 -85 4.02 0.5988
WVFGRD96 20.0 290 50 -85 4.04 0.6012
WVFGRD96 21.0 290 50 -80 4.05 0.5983
WVFGRD96 22.0 290 50 -80 4.05 0.5936
WVFGRD96 23.0 295 50 -75 4.06 0.5874
WVFGRD96 24.0 295 50 -75 4.06 0.5795
WVFGRD96 25.0 295 50 -75 4.07 0.5702
WVFGRD96 26.0 295 50 -75 4.07 0.5598
WVFGRD96 27.0 295 50 -75 4.08 0.5484
WVFGRD96 28.0 295 50 -75 4.08 0.5363
WVFGRD96 29.0 295 50 -75 4.09 0.5232
The best solution is
WVFGRD96 20.0 290 50 -85 4.04 0.6012
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
cut o DIST/3.3 -20 o DIST/3.3 +40 rtr taper w 0.1 hp c 0.03 n 3 lp c 0.08 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 CUS.model 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: