Location
2015/01/04 07:34:13 44.493 -114.1190 10.0 4.0 Idaho
Arrival Times (from USGS)
Arrival time list
Felt Map
USGS Felt map for this earthquake
USGS Felt reports main page
Focal Mechanism
USGS/SLU Moment Tensor Solution
ENS 2015/01/04 07:34:13:0 44.49 -114.12 10.0 4.0 Idaho
Stations used:
CN.WALA IM.PD31 IW.DLMT IW.FLWY IW.LOHW IW.MFID IW.MOOW
IW.REDW MB.JTMT TA.H17A UO.PINE US.AHID US.BMO US.BOZ
US.BW06 US.DUG US.EGMT US.ELK US.HAWA US.HLID US.MSO
US.RLMT US.WVOR UU.BGU UU.CTU UU.HVU UU.JLU UU.MPU UU.SPU
UW.BRAN UW.CCRK UW.DDRF UW.IZEE UW.LTY UW.TREE UW.TUCA
UW.UMAT UW.WOLL WY.YHB WY.YHH WY.YHL WY.YMR WY.YNE WY.YNR
WY.YPP
Filtering commands used:
cut o DIST/3.3 -30 o DIST/3.3 +70
rtr
taper w 0.1
hp c 0.03 n 3
lp c 0.07 n 3
Best Fitting Double Couple
Mo = 6.31e+21 dyne-cm
Mw = 3.80
Z = 14 km
Plane Strike Dip Rake
NP1 150 75 -80
NP2 296 18 -123
Principal Axes:
Axis Value Plunge Azimuth
T 6.31e+21 29 232
N 0.00e+00 10 327
P -6.31e+21 59 74
Moment Tensor: (dyne-cm)
Component Value
Mxx 1.69e+21
Mxy 1.87e+21
Mxz -2.45e+21
Myy 1.41e+21
Myz -4.80e+21
Mzz -3.11e+21
##############
-######----###########
---#-----------------#######
-####--------------------#####
-#######----------------------####
#########------------------------###
###########------------------------###
#############------------------------###
#############------------- ---------##
###############------------ P ----------##
################----------- ----------##
#################-----------------------##
##################-----------------------#
##################---------------------#
####### ##########-------------------#
###### T ###########------------------
##### ############----------------
#####################-------------
####################----------
#####################-------
#####################-
##############
Global CMT Convention Moment Tensor:
R T P
-3.11e+21 -2.45e+21 4.80e+21
-2.45e+21 1.69e+21 -1.87e+21
4.80e+21 -1.87e+21 1.41e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20150104073413/index.html
|
Preferred Solution
The preferred solution from an analysis of the surface-wave spectral amplitude radiation pattern, waveform inversion and first motion observations is
STK = 150
DIP = 75
RAKE = -80
MW = 3.80
HS = 14.0
The NDK file is 20150104073413.ndk
The waveform inversion is preferred.
Moment Tensor Comparison
The following compares this source inversion to others
| SLU |
USGSMT |
USGS/SLU Moment Tensor Solution
ENS 2015/01/04 07:34:13:0 44.49 -114.12 10.0 4.0 Idaho
Stations used:
CN.WALA IM.PD31 IW.DLMT IW.FLWY IW.LOHW IW.MFID IW.MOOW
IW.REDW MB.JTMT TA.H17A UO.PINE US.AHID US.BMO US.BOZ
US.BW06 US.DUG US.EGMT US.ELK US.HAWA US.HLID US.MSO
US.RLMT US.WVOR UU.BGU UU.CTU UU.HVU UU.JLU UU.MPU UU.SPU
UW.BRAN UW.CCRK UW.DDRF UW.IZEE UW.LTY UW.TREE UW.TUCA
UW.UMAT UW.WOLL WY.YHB WY.YHH WY.YHL WY.YMR WY.YNE WY.YNR
WY.YPP
Filtering commands used:
cut o DIST/3.3 -30 o DIST/3.3 +70
rtr
taper w 0.1
hp c 0.03 n 3
lp c 0.07 n 3
Best Fitting Double Couple
Mo = 6.31e+21 dyne-cm
Mw = 3.80
Z = 14 km
Plane Strike Dip Rake
NP1 150 75 -80
NP2 296 18 -123
Principal Axes:
Axis Value Plunge Azimuth
T 6.31e+21 29 232
N 0.00e+00 10 327
P -6.31e+21 59 74
Moment Tensor: (dyne-cm)
Component Value
Mxx 1.69e+21
Mxy 1.87e+21
Mxz -2.45e+21
Myy 1.41e+21
Myz -4.80e+21
Mzz -3.11e+21
##############
-######----###########
---#-----------------#######
-####--------------------#####
-#######----------------------####
#########------------------------###
###########------------------------###
#############------------------------###
#############------------- ---------##
###############------------ P ----------##
################----------- ----------##
#################-----------------------##
##################-----------------------#
##################---------------------#
####### ##########-------------------#
###### T ###########------------------
##### ############----------------
#####################-------------
####################----------
#####################-------
#####################-
##############
Global CMT Convention Moment Tensor:
R T P
-3.11e+21 -2.45e+21 4.80e+21
-2.45e+21 1.69e+21 -1.87e+21
4.80e+21 -1.87e+21 1.41e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20150104073413/index.html
|
Moment
6.66e+14 N-m
Magnitude
3.8
Percent DC
97%
Depth
12.0 km
Updated
2015-01-04 14:17:24 UTC
Author
us
Catalog
Contributor
us
Code
us_c000tbk8_mwr
Principal Axes
Axis Value Plunge Azimuth
T 6.695 25 235
N -0.077 5 327
P -6.618 64 69
Nodal Planes
Plane Strike Dip Rake
NP1 149 70 -84
NP2 313 20 -106
|
Magnitudes
ML Magnitude
(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.
Context
The next figure presents the focal mechanism for this earthquake (red) in the context of other events (blue) in the SLU Moment Tensor Catalog which are within ± 0.5 degrees of the new event. This comparison is shown in the left panel of the figure. The right panel shows the inferred direction of maximum compressive stress and the type of faulting (green is strike-slip, red is normal, blue is thrust; oblique is shown by a combination of colors).
Waveform Inversion
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.
|
|
Location of broadband stations used for waveform inversion
|
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 -30 o DIST/3.3 +70
rtr
taper w 0.1
hp c 0.03 n 3
lp c 0.07 n 3
The results of this grid search from 0.5 to 19 km depth are as follow:
DEPTH STK DIP RAKE MW FIT
WVFGRD96 1.0 160 50 -90 3.54 0.4094
WVFGRD96 2.0 340 40 -90 3.63 0.4510
WVFGRD96 3.0 350 35 -85 3.68 0.3500
WVFGRD96 4.0 235 15 -5 3.73 0.4025
WVFGRD96 5.0 240 15 0 3.72 0.4613
WVFGRD96 6.0 245 15 5 3.71 0.4978
WVFGRD96 7.0 245 20 5 3.70 0.5173
WVFGRD96 8.0 235 15 -10 3.77 0.5263
WVFGRD96 9.0 150 80 -85 3.77 0.5375
WVFGRD96 10.0 150 75 -85 3.78 0.5621
WVFGRD96 11.0 150 75 -80 3.78 0.5806
WVFGRD96 12.0 150 75 -80 3.79 0.5928
WVFGRD96 13.0 150 75 -80 3.79 0.5998
WVFGRD96 14.0 150 75 -80 3.80 0.6019
WVFGRD96 15.0 150 80 -75 3.80 0.6004
WVFGRD96 16.0 150 80 -75 3.81 0.5967
WVFGRD96 17.0 150 80 -75 3.81 0.5904
WVFGRD96 18.0 150 80 -75 3.82 0.5818
WVFGRD96 19.0 150 80 -75 3.82 0.5717
WVFGRD96 20.0 150 80 -70 3.84 0.5604
WVFGRD96 21.0 150 80 -70 3.85 0.5487
WVFGRD96 22.0 155 85 -70 3.85 0.5349
WVFGRD96 23.0 155 85 -70 3.86 0.5208
WVFGRD96 24.0 155 85 -70 3.87 0.5059
WVFGRD96 25.0 155 85 -65 3.88 0.4904
WVFGRD96 26.0 155 85 -70 3.88 0.4744
WVFGRD96 27.0 155 85 -70 3.89 0.4580
WVFGRD96 28.0 155 90 -65 3.90 0.4412
WVFGRD96 29.0 335 90 65 3.90 0.4242
The best solution is
WVFGRD96 14.0 150 75 -80 3.80 0.6019
The mechanism correspond to the best fit is
|
|
Figure 1. Waveform inversion focal mechanism
|
The best fit as a function of depth is given in the following figure:
|
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Figure 2. Depth sensitivity for waveform mechanism
|
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 -30 o DIST/3.3 +70
rtr
taper w 0.1
hp c 0.03 n 3
lp c 0.07 n 3
|
|
Figure 3. Waveform comparison for selected depth. Red: observed; Blue - predicted. The time shift with respect to the model prediction is indicated. The percent of fit is also indicated.
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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:
- The origin time and epicentral distance are incorrect
- The velocity model used for the inversion is incorrect
- The velocity model used to define the P-arrival time is not the
same as the velocity model used for the waveform inversion
(assuming that the initial trace alignment is based on the
P arrival time)
Assuming only a mislocation, the time shifts are fit to a functional form:
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.
Discussion
Acknowledgements
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.
Velocity Model
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
Quality Control
Here we tabulate the reasons for not using certain digital data sets
The following stations did not have a valid response files:
Last Changed Mon Dec 7 00:40:12 CST 2015
