2010/07/30 11:13:46 38.615 -118.215 9 4.20 Nevada
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2010/07/30 11:13:46:0 38.62 -118.21 9.0 4.2 Nevada
Stations used:
BK.CMB BK.WDC BK.YBH CI.GSC CI.ISA CI.LDF CI.OSI CI.PASC
LB.DAC LB.TPH US.DUG US.ELK US.TPNV US.WVOR UU.BGU UU.CCUT
UU.MTPU UU.PSUT UU.TCRU UW.TREE
Filtering commands used:
hp c 0.02 n 3
lp c 0.06 n 3
Best Fitting Double Couple
Mo = 6.10e+21 dyne-cm
Mw = 3.79
Z = 14 km
Plane Strike Dip Rake
NP1 70 85 15
NP2 339 75 175
Principal Axes:
Axis Value Plunge Azimuth
T 6.10e+21 14 295
N 0.00e+00 74 88
P -6.10e+21 7 203
Moment Tensor: (dyne-cm)
Component Value
Mxx -4.01e+21
Mxy -4.41e+21
Mxz 1.28e+21
Myy 3.74e+21
Myz -1.01e+21
Mzz 2.74e+20
--------------
#####-----------------
##########------------------
############------------------
###############-------------------
##############-------------------
# T ###############-------------------
## ################-----------------##
######################-------------#####
########################--------##########
#########################--###############
######################---#################
#################---------################
##########----------------##############
###-----------------------##############
--------------------------############
-------------------------###########
------------------------##########
-----------------------#######
----- --------------######
-- P --------------###
-------------
Global CMT Convention Moment Tensor:
R T P
2.74e+20 1.28e+21 1.01e+21
1.28e+21 -4.01e+21 4.41e+21
1.01e+21 4.41e+21 3.74e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20100730111346/index.html
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STK = 70
DIP = 85
RAKE = 15
MW = 3.79
HS = 14.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2010/07/30 11:13:46:0 38.62 -118.21 9.0 4.2 Nevada
Stations used:
BK.CMB BK.WDC BK.YBH CI.GSC CI.ISA CI.LDF CI.OSI CI.PASC
LB.DAC LB.TPH US.DUG US.ELK US.TPNV US.WVOR UU.BGU UU.CCUT
UU.MTPU UU.PSUT UU.TCRU UW.TREE
Filtering commands used:
hp c 0.02 n 3
lp c 0.06 n 3
Best Fitting Double Couple
Mo = 6.10e+21 dyne-cm
Mw = 3.79
Z = 14 km
Plane Strike Dip Rake
NP1 70 85 15
NP2 339 75 175
Principal Axes:
Axis Value Plunge Azimuth
T 6.10e+21 14 295
N 0.00e+00 74 88
P -6.10e+21 7 203
Moment Tensor: (dyne-cm)
Component Value
Mxx -4.01e+21
Mxy -4.41e+21
Mxz 1.28e+21
Myy 3.74e+21
Myz -1.01e+21
Mzz 2.74e+20
--------------
#####-----------------
##########------------------
############------------------
###############-------------------
##############-------------------
# T ###############-------------------
## ################-----------------##
######################-------------#####
########################--------##########
#########################--###############
######################---#################
#################---------################
##########----------------##############
###-----------------------##############
--------------------------############
-------------------------###########
------------------------##########
-----------------------#######
----- --------------######
-- P --------------###
-------------
Global CMT Convention Moment Tensor:
R T P
2.74e+20 1.28e+21 1.01e+21
1.28e+21 -4.01e+21 4.41e+21
1.01e+21 4.41e+21 3.74e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20100730111346/index.html
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Seismic Moment Tensor Solution
2010/07/30 (211) 11:13:47.00 38.6149 -118.2151 746209
Depth = 10.0 (km)
Mw = 3.80
Mo = 6.34x10^21 (dyne x cm)
Percent Double Couple = 97 %
Percent CLVD = 3 %
no ISO calculated
Epsilon=0.02
Percent Variance Reduction = 46.36 %
Total Fit = 11.11
Major Double Couple
strike dip rake
Nodal Plane 1: 340 71 164
Nodal Plane 2: 75 75 19
DEVIATORIC MOMENT TENSOR
Moment Tensor Elements: Spherical Coordinates
Mrr= 1.13 Mtt= -3.86 Mff= 2.74
Mrt= 1.34 Mrf= 1.91 Mtf= 4.79 EXP=21
Moment Tensor Elements: Cartesian Coordinates
-3.86 -4.79 1.34
-4.79 2.74 -1.91
1.34 -1.91 1.13
Eigenvalues:
T-axis eigenvalue= 6.29
N-axis eigenvalue= 0.10
P-axis eigenvalue= -6.39
Eigenvalues and eigenvectors of the Major Double Couple:
T-axis ev= 6.29 trend=298 plunge=24
N-axis ev= 0.00 trend=112 plunge=66
P-axis ev=-6.29 trend=207 plunge=2
Maximum Azmuithal Gap=176 Distance to Nearest Station=105.1 (km)
Number of Stations (D=Displacement/V=Velocity) Used=6 (defining only)
TPH.LB.D MLAC.CI.D TIN.CI.D GRA.CI.D
BMN.LB.D R11A.TA.D
##---------------
########-----------------
############-----------------
###############------------------
#################------------------
##################------------------
T ###################-------------------
####################------------------
#########################------------------
##########################--------------###
##########################-----------#######
###########################-------##########
############################-###############
############################################
########################---################
-###############------------###############
---------------------------##############
---------------------------#############
---------------------------############
-------------------------###########
------------------------#########
- ------------------#######
P ------------------#####
---------------###
All Stations defining and nondefining:
Station.Net Def Distance Azi Bazi lo-f hi-f vmodel
(km) (deg) (deg) (Hz) (Hz)
TPH.LB (D) Y 105.1 124 305 0.020 0.080 TPH.LB.wus.glib
MLAC.CI (D) Y 122.3 207 26 0.020 0.080 MLAC.CI.wus.glib
TIN.CI (D) Y 173.9 180 0 0.020 0.080 TIN.CI.wus.glib
GRA.CI (D) Y 194.2 157 338 0.020 0.080 GRA.CI.wus.glib
BMN.LB (D) Y 219.0 23 203 0.020 0.080 BMN.LB.wus.glib
R11A.TA (D) Y 230.2 97 278 0.020 0.080 R11A.TA.wus.glib
(V)-velocity (D)-Displacement
Author: ken
Date: 2010/07/30 12:32:06
mtinv Version 2.1_DEVEL OCT2008
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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 75 65 20 3.45 0.3758
WVFGRD96 1.0 70 75 10 3.44 0.4006
WVFGRD96 2.0 75 65 20 3.56 0.4897
WVFGRD96 3.0 70 75 10 3.57 0.5313
WVFGRD96 4.0 70 80 10 3.59 0.5596
WVFGRD96 5.0 70 75 20 3.63 0.5866
WVFGRD96 6.0 70 80 20 3.65 0.6148
WVFGRD96 7.0 70 80 15 3.67 0.6422
WVFGRD96 8.0 70 80 20 3.71 0.6693
WVFGRD96 9.0 70 85 20 3.72 0.6896
WVFGRD96 10.0 250 90 -20 3.74 0.7052
WVFGRD96 11.0 250 90 -20 3.75 0.7181
WVFGRD96 12.0 70 85 15 3.76 0.7278
WVFGRD96 13.0 250 90 -15 3.78 0.7314
WVFGRD96 14.0 70 85 15 3.79 0.7350
WVFGRD96 15.0 250 85 -15 3.80 0.7334
WVFGRD96 16.0 70 85 10 3.81 0.7321
WVFGRD96 17.0 70 85 10 3.81 0.7274
WVFGRD96 18.0 70 85 10 3.82 0.7205
WVFGRD96 19.0 70 85 10 3.83 0.7119
WVFGRD96 20.0 70 85 10 3.84 0.7021
WVFGRD96 21.0 250 90 -10 3.85 0.6902
WVFGRD96 22.0 70 85 5 3.86 0.6790
WVFGRD96 23.0 250 90 -10 3.86 0.6650
WVFGRD96 24.0 70 85 5 3.87 0.6533
WVFGRD96 25.0 250 90 -5 3.88 0.6372
WVFGRD96 26.0 70 85 5 3.88 0.6247
WVFGRD96 27.0 70 85 5 3.89 0.6097
WVFGRD96 28.0 250 90 -5 3.90 0.5919
WVFGRD96 29.0 250 90 -5 3.90 0.5762
The best solution is
WVFGRD96 14.0 70 85 15 3.79 0.7350
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 0.06 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. |
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 WUS 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:
DATE=Fri Jul 30 11:18:49 CDT 2010