2014/04/03 01:58:31 -20.268 -70.556 22.8 6.5 Chile
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2014/04/03 01:58:31:0 -20.27 -70.56 22.8 6.5 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 = 4.22e+25 dyne-cm
Mw = 6.35
Z = 32 km
Plane Strike Dip Rake
NP1 175 70 80
NP2 22 22 116
Principal Axes:
Axis Value Plunge Azimuth
T 4.22e+25 64 69
N 0.00e+00 9 178
P -4.22e+25 24 273
Moment Tensor: (dyne-cm)
Component Value
Mxx 9.92e+23
Mxy 4.46e+24
Mxz 5.27e+24
Myy -2.77e+25
Myz 3.15e+25
Mzz 2.67e+25
-----#########
--------#############-
----------################--
-----------#################--
------------###################---
-------------####################---
--------------#####################---
---------------#####################----
---------------########## #########---
---- ---------########## T #########----
---- P ---------########## #########----
---- ---------######################----
----------------#####################-----
---------------#####################----
----------------###################-----
---------------##################-----
---------------################-----
--------------###############-----
-------------############-----
-------------#########------
-----------####-------
-----###------
Global CMT Convention Moment Tensor:
R T P
2.67e+25 5.27e+24 -3.15e+25
5.27e+24 9.92e+23 -4.46e+24
-3.15e+25 -4.46e+24 -2.77e+25
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20140403015831/index.html
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STK = 175
DIP = 70
RAKE = 80
MW = 6.35
HS = 32.0
The NDK file is 20140403015831.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2014/04/03 01:58:31:0 -20.27 -70.56 22.8 6.5 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 = 4.22e+25 dyne-cm
Mw = 6.35
Z = 32 km
Plane Strike Dip Rake
NP1 175 70 80
NP2 22 22 116
Principal Axes:
Axis Value Plunge Azimuth
T 4.22e+25 64 69
N 0.00e+00 9 178
P -4.22e+25 24 273
Moment Tensor: (dyne-cm)
Component Value
Mxx 9.92e+23
Mxy 4.46e+24
Mxz 5.27e+24
Myy -2.77e+25
Myz 3.15e+25
Mzz 2.67e+25
-----#########
--------#############-
----------################--
-----------#################--
------------###################---
-------------####################---
--------------#####################---
---------------#####################----
---------------########## #########---
---- ---------########## T #########----
---- P ---------########## #########----
---- ---------######################----
----------------#####################-----
---------------#####################----
----------------###################-----
---------------##################-----
---------------################-----
--------------###############-----
-------------############-----
-------------#########------
-----------####-------
-----###------
Global CMT Convention Moment Tensor:
R T P
2.67e+25 5.27e+24 -3.15e+25
5.27e+24 9.92e+23 -4.46e+24
-3.15e+25 -4.46e+24 -2.77e+25
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20140403015831/index.html
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The USGS and other MT's are
Type Magnitude Depth NP1 NP2 Author Catalog Contributor
Mwb 6.5 28.0 km 173, 65, 79 18, 27, 112 us us us
Mww 6.5 19.5 km 162, 67, 80 7, 25, 113 us us us
Mww 6.5 19.5 km 162, 67, 80 7, 25, 113 us us us
Mwc 6.6 33.8 km 165, 67, 87 352, 23, 96 gcmt gcmt us
Mwr 6.35 32 km 175, 70, 80 22, 22, 116 SLU 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 20 45 -90 5.98 0.3404
WVFGRD96 4.0 90 85 -5 5.94 0.2974
WVFGRD96 6.0 265 30 -10 6.02 0.2921
WVFGRD96 8.0 255 20 -20 6.12 0.3630
WVFGRD96 10.0 250 20 -25 6.14 0.4529
WVFGRD96 12.0 250 20 -25 6.16 0.5273
WVFGRD96 14.0 245 20 -30 6.19 0.5882
WVFGRD96 16.0 250 20 -25 6.21 0.6380
WVFGRD96 18.0 335 20 65 6.23 0.6807
WVFGRD96 20.0 345 20 75 6.25 0.7278
WVFGRD96 22.0 350 20 80 6.27 0.7665
WVFGRD96 24.0 175 70 90 6.29 0.7990
WVFGRD96 26.0 175 70 85 6.31 0.8252
WVFGRD96 28.0 175 70 85 6.32 0.8426
WVFGRD96 30.0 10 20 105 6.34 0.8500
WVFGRD96 32.0 175 70 80 6.35 0.8500
WVFGRD96 34.0 175 70 80 6.37 0.8409
WVFGRD96 36.0 175 70 80 6.37 0.8252
WVFGRD96 38.0 175 70 80 6.38 0.8055
WVFGRD96 40.0 175 75 85 6.52 0.7751
WVFGRD96 42.0 175 75 85 6.53 0.7516
WVFGRD96 44.0 175 70 80 6.53 0.7277
WVFGRD96 46.0 175 70 80 6.54 0.7040
WVFGRD96 48.0 175 70 80 6.55 0.6791
WVFGRD96 50.0 175 70 80 6.56 0.6534
WVFGRD96 52.0 175 75 80 6.56 0.6287
WVFGRD96 54.0 175 75 80 6.57 0.6055
WVFGRD96 56.0 175 75 80 6.57 0.5832
WVFGRD96 58.0 175 75 80 6.58 0.5620
WVFGRD96 60.0 170 75 80 6.57 0.5417
WVFGRD96 62.0 170 75 80 6.58 0.5228
WVFGRD96 64.0 170 75 80 6.58 0.5046
WVFGRD96 66.0 170 80 80 6.58 0.4904
WVFGRD96 68.0 170 80 80 6.59 0.4766
WVFGRD96 70.0 170 80 80 6.59 0.4637
WVFGRD96 72.0 170 80 80 6.59 0.4516
WVFGRD96 74.0 170 80 85 6.60 0.4399
WVFGRD96 76.0 170 85 80 6.60 0.4285
WVFGRD96 78.0 170 85 80 6.60 0.4203
WVFGRD96 80.0 165 85 80 6.60 0.4121
WVFGRD96 82.0 350 90 -80 6.60 0.3988
WVFGRD96 84.0 345 90 -80 6.60 0.3951
WVFGRD96 86.0 345 90 -80 6.60 0.3926
WVFGRD96 88.0 165 90 80 6.61 0.3894
WVFGRD96 90.0 165 90 80 6.61 0.3856
WVFGRD96 92.0 345 90 -80 6.62 0.3822
WVFGRD96 94.0 345 85 -80 6.61 0.3820
WVFGRD96 96.0 165 90 80 6.62 0.3738
WVFGRD96 98.0 345 85 -80 6.62 0.3819
WVFGRD96 100.0 345 85 -80 6.63 0.3808
WVFGRD96 102.0 345 80 -80 6.62 0.3792
WVFGRD96 104.0 345 80 -80 6.62 0.3808
WVFGRD96 106.0 345 80 -80 6.63 0.3816
WVFGRD96 108.0 345 80 -80 6.63 0.3818
The best solution is
WVFGRD96 32.0 175 70 80 6.35 0.8500
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: