2014/04/04 01:37:51 -20.621 -70.739 20.0 6.1 Chile
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2014/04/04 01:37:51:0 -20.62 -70.74 20.0 6.1 Chile
Stations used:
CX.MNMCX CX.PB01 CX.PB04 CX.PB07 CX.PB09 CX.PB10 CX.PB11
CX.PB12 CX.PB14 CX.PB15 CX.PB16 CX.PSGCX GT.LPAZ IU.LVC
Filtering commands used:
cut a -30 a 180
rtr
taper w 0.1
hp c 0.02 n 3
lp c 0.06 n 3
Best Fitting Double Couple
Mo = 1.40e+25 dyne-cm
Mw = 6.03
Z = 24 km
Plane Strike Dip Rake
NP1 165 60 75
NP2 13 33 114
Principal Axes:
Axis Value Plunge Azimuth
T 1.40e+25 71 41
N 0.00e+00 13 173
P -1.40e+25 14 266
Moment Tensor: (dyne-cm)
Component Value
Mxx 7.82e+23
Mxy -2.10e+23
Mxz 3.49e+24
Myy -1.25e+25
Myz 6.05e+24
Mzz 1.17e+25
-############-
----###############---
-------#################----
-------###################----
---------####################-----
---------######################-----
----------######################------
-----------#######################------
-----------########## ##########------
-------------######### T ##########-------
- ---------######### ##########-------
- P ---------######################-------
- ----------#####################-------
-------------####################-------
--------------###################-------
--------------#################-------
--------------###############-------
--------------############--------
-------------##########-------
--------------######--------
-------------#--------
------#####---
Global CMT Convention Moment Tensor:
R T P
1.17e+25 3.49e+24 -6.05e+24
3.49e+24 7.82e+23 2.10e+23
-6.05e+24 2.10e+23 -1.25e+25
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20140404013751/index.html
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STK = 165
DIP = 60
RAKE = 75
MW = 6.03
HS = 24.0
The NDK file is 20140404013751.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2014/04/04 01:37:51:0 -20.62 -70.74 20.0 6.1 Chile
Stations used:
CX.MNMCX CX.PB01 CX.PB04 CX.PB07 CX.PB09 CX.PB10 CX.PB11
CX.PB12 CX.PB14 CX.PB15 CX.PB16 CX.PSGCX GT.LPAZ IU.LVC
Filtering commands used:
cut a -30 a 180
rtr
taper w 0.1
hp c 0.02 n 3
lp c 0.06 n 3
Best Fitting Double Couple
Mo = 1.40e+25 dyne-cm
Mw = 6.03
Z = 24 km
Plane Strike Dip Rake
NP1 165 60 75
NP2 13 33 114
Principal Axes:
Axis Value Plunge Azimuth
T 1.40e+25 71 41
N 0.00e+00 13 173
P -1.40e+25 14 266
Moment Tensor: (dyne-cm)
Component Value
Mxx 7.82e+23
Mxy -2.10e+23
Mxz 3.49e+24
Myy -1.25e+25
Myz 6.05e+24
Mzz 1.17e+25
-############-
----###############---
-------#################----
-------###################----
---------####################-----
---------######################-----
----------######################------
-----------#######################------
-----------########## ##########------
-------------######### T ##########-------
- ---------######### ##########-------
- P ---------######################-------
- ----------#####################-------
-------------####################-------
--------------###################-------
--------------#################-------
--------------###############-------
--------------############--------
-------------##########-------
--------------######--------
-------------#--------
------#####---
Global CMT Convention Moment Tensor:
R T P
1.17e+25 3.49e+24 -6.05e+24
3.49e+24 7.82e+23 2.10e+23
-6.05e+24 2.10e+23 -1.25e+25
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20140404013751/index.html
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Type Magnitude Depth NP1 NP2 Author Catalog Contributor
Mww 6.1 25.5 km 161, 70, 82 5, 22, 112 us us us
Mwb 6.1 20.0 km 157, 58, 85 347, 32, 98 us us us
Mwc 6.3 18.3 km 156, 70, 80 3, 22, 115 gcmt gcmt us
Mwr 6.03 24 km 165, 60, 75 13, 33, 114 SLU
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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 a -30 a 180 rtr taper w 0.1 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 2.0 80 85 -10 5.65 0.3524
WVFGRD96 4.0 80 90 -30 5.73 0.3383
WVFGRD96 6.0 260 25 -5 5.80 0.3578
WVFGRD96 8.0 255 20 -10 5.89 0.4282
WVFGRD96 10.0 245 20 -25 5.91 0.5069
WVFGRD96 12.0 245 20 -25 5.92 0.5632
WVFGRD96 14.0 165 70 85 5.94 0.6139
WVFGRD96 16.0 165 65 80 5.96 0.6687
WVFGRD96 18.0 165 60 80 5.98 0.7097
WVFGRD96 20.0 165 60 75 6.00 0.7358
WVFGRD96 22.0 165 60 75 6.02 0.7483
WVFGRD96 24.0 165 60 75 6.03 0.7523
WVFGRD96 26.0 160 65 75 6.04 0.7497
WVFGRD96 28.0 160 65 75 6.06 0.7402
WVFGRD96 30.0 160 65 75 6.07 0.7241
WVFGRD96 32.0 160 65 75 6.08 0.7019
WVFGRD96 34.0 165 65 80 6.09 0.6744
WVFGRD96 36.0 165 65 80 6.10 0.6431
WVFGRD96 38.0 165 65 80 6.11 0.6099
WVFGRD96 40.0 165 70 85 6.24 0.5776
WVFGRD96 42.0 165 70 85 6.25 0.5400
WVFGRD96 44.0 165 70 85 6.25 0.4993
WVFGRD96 46.0 165 70 85 6.25 0.4586
WVFGRD96 48.0 165 70 85 6.26 0.4191
WVFGRD96 50.0 165 70 85 6.25 0.3816
WVFGRD96 52.0 165 70 85 6.25 0.3466
WVFGRD96 54.0 160 75 -45 6.28 0.3227
WVFGRD96 56.0 160 75 -45 6.29 0.3145
WVFGRD96 58.0 160 80 -45 6.29 0.3105
WVFGRD96 60.0 160 80 -45 6.30 0.3073
WVFGRD96 62.0 160 85 -50 6.31 0.3042
WVFGRD96 64.0 345 90 45 6.31 0.3001
WVFGRD96 66.0 160 85 -50 6.32 0.3018
WVFGRD96 68.0 345 90 45 6.33 0.2978
WVFGRD96 70.0 155 90 -45 6.32 0.2953
WVFGRD96 72.0 155 90 -45 6.33 0.2937
WVFGRD96 74.0 155 90 -45 6.34 0.2931
WVFGRD96 76.0 155 90 -45 6.35 0.2916
WVFGRD96 78.0 155 90 -45 6.35 0.2917
WVFGRD96 80.0 155 90 -45 6.36 0.2917
WVFGRD96 82.0 155 90 -45 6.36 0.2895
WVFGRD96 84.0 335 85 45 6.36 0.2891
WVFGRD96 86.0 155 90 -45 6.37 0.2842
WVFGRD96 88.0 170 35 80 6.32 0.2860
WVFGRD96 90.0 165 40 75 6.32 0.2867
WVFGRD96 92.0 165 40 75 6.32 0.2859
WVFGRD96 94.0 165 40 75 6.32 0.2864
WVFGRD96 96.0 145 35 55 6.33 0.2882
WVFGRD96 98.0 155 40 65 6.33 0.2922
WVFGRD96 100.0 155 40 65 6.33 0.2979
WVFGRD96 102.0 155 40 65 6.33 0.3042
WVFGRD96 104.0 160 40 70 6.33 0.3070
WVFGRD96 106.0 160 40 70 6.34 0.3121
WVFGRD96 108.0 160 40 70 6.34 0.3159
The best solution is
WVFGRD96 24.0 165 60 75 6.03 0.7523
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 a -30 a 180 rtr taper w 0.1 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. |
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 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: