2014/03/23 18:19:59 -19.771 -70.947 6.2 6.1 Chile
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2014/03/23 18:19:59:0 -19.77 -70.95 6.2 6.1 Chile
Stations used:
CX.PATCX 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 = 2.19e+25 dyne-cm
Mw = 6.16
Z = 26 km
Plane Strike Dip Rake
NP1 155 65 90
NP2 335 25 90
Principal Axes:
Axis Value Plunge Azimuth
T 2.19e+25 70 65
N 0.00e+00 -0 335
P -2.19e+25 20 245
Moment Tensor: (dyne-cm)
Component Value
Mxx -2.99e+24
Mxy -6.42e+24
Mxz 5.94e+24
Myy -1.38e+25
Myz 1.27e+25
Mzz 1.68e+25
--------------
--############--------
-----################-------
-----###################------
-------#####################------
---------#####################------
----------######################------
-----------#######################------
------------############ ########-----
-------------############ T #########-----
--------------########### #########-----
--------------#######################-----
---------------######################-----
--- ---------#####################----
--- P ----------####################----
-- -----------###################---
-----------------################---
-----------------##############---
-----------------###########--
------------------########--
-----------------####-
--------------
Global CMT Convention Moment Tensor:
R T P
1.68e+25 5.94e+24 -1.27e+25
5.94e+24 -2.99e+24 6.42e+24
-1.27e+25 6.42e+24 -1.38e+25
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20140323181959/index.html
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STK = 335
DIP = 25
RAKE = 90
MW = 6.16
HS = 26.0
The NDK file is 20140323181959.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2014/03/23 18:19:59:0 -19.77 -70.95 6.2 6.1 Chile
Stations used:
CX.PATCX 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 = 2.19e+25 dyne-cm
Mw = 6.16
Z = 26 km
Plane Strike Dip Rake
NP1 155 65 90
NP2 335 25 90
Principal Axes:
Axis Value Plunge Azimuth
T 2.19e+25 70 65
N 0.00e+00 -0 335
P -2.19e+25 20 245
Moment Tensor: (dyne-cm)
Component Value
Mxx -2.99e+24
Mxy -6.42e+24
Mxz 5.94e+24
Myy -1.38e+25
Myz 1.27e+25
Mzz 1.68e+25
--------------
--############--------
-----################-------
-----###################------
-------#####################------
---------#####################------
----------######################------
-----------#######################------
------------############ ########-----
-------------############ T #########-----
--------------########### #########-----
--------------#######################-----
---------------######################-----
--- ---------#####################----
--- P ----------####################----
-- -----------###################---
-----------------################---
-----------------##############---
-----------------###########--
------------------########--
-----------------####-
--------------
Global CMT Convention Moment Tensor:
R T P
1.68e+25 5.94e+24 -1.27e+25
5.94e+24 -2.99e+24 6.42e+24
-1.27e+25 6.42e+24 -1.38e+25
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20140323181959/index.html
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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 2.0 160 40 90 5.85 0.4139
WVFGRD96 4.0 155 30 80 5.91 0.2916
WVFGRD96 6.0 245 15 -15 5.92 0.4174
WVFGRD96 8.0 240 10 -20 6.00 0.5091
WVFGRD96 10.0 235 10 -20 6.01 0.6058
WVFGRD96 12.0 235 15 -20 6.03 0.6762
WVFGRD96 14.0 235 15 -20 6.05 0.7267
WVFGRD96 16.0 295 15 45 6.07 0.7624
WVFGRD96 18.0 310 15 60 6.08 0.7948
WVFGRD96 20.0 330 20 85 6.11 0.8194
WVFGRD96 22.0 330 20 85 6.13 0.8362
WVFGRD96 24.0 330 20 85 6.14 0.8456
WVFGRD96 26.0 335 25 90 6.16 0.8480
WVFGRD96 28.0 335 25 90 6.17 0.8451
WVFGRD96 30.0 155 65 90 6.18 0.8360
WVFGRD96 32.0 335 25 90 6.19 0.8202
WVFGRD96 34.0 155 65 90 6.20 0.7983
WVFGRD96 36.0 155 65 90 6.21 0.7718
WVFGRD96 38.0 330 25 85 6.23 0.7437
WVFGRD96 40.0 335 20 90 6.35 0.7190
WVFGRD96 42.0 335 20 90 6.36 0.6881
WVFGRD96 44.0 335 20 90 6.37 0.6563
WVFGRD96 46.0 335 20 90 6.37 0.6246
WVFGRD96 48.0 335 20 90 6.38 0.5930
WVFGRD96 50.0 340 20 95 6.39 0.5624
WVFGRD96 52.0 340 20 95 6.39 0.5334
WVFGRD96 54.0 330 20 80 6.40 0.5063
WVFGRD96 56.0 340 15 95 6.40 0.4815
WVFGRD96 58.0 345 15 100 6.40 0.4612
WVFGRD96 60.0 335 15 85 6.41 0.4434
WVFGRD96 62.0 330 15 80 6.41 0.4268
WVFGRD96 64.0 340 10 95 6.42 0.4130
WVFGRD96 66.0 325 10 75 6.42 0.4034
WVFGRD96 68.0 320 10 70 6.43 0.3947
WVFGRD96 70.0 305 10 55 6.43 0.3867
WVFGRD96 72.0 310 5 60 6.44 0.3821
WVFGRD96 74.0 295 5 45 6.44 0.3780
WVFGRD96 76.0 230 0 -15 6.44 0.3738
WVFGRD96 78.0 140 0 -105 6.45 0.3722
WVFGRD96 80.0 335 85 -75 6.44 0.3726
WVFGRD96 82.0 200 5 -45 6.46 0.3731
WVFGRD96 84.0 190 5 -55 6.47 0.3749
WVFGRD96 86.0 180 5 -65 6.48 0.3759
WVFGRD96 88.0 190 10 -55 6.47 0.3771
WVFGRD96 90.0 325 65 -85 6.44 0.3825
WVFGRD96 92.0 325 65 -85 6.45 0.3905
WVFGRD96 94.0 325 65 -85 6.45 0.3965
WVFGRD96 96.0 135 25 -100 6.46 0.4023
WVFGRD96 98.0 135 25 -100 6.47 0.4068
WVFGRD96 100.0 140 30 -90 6.47 0.4118
WVFGRD96 102.0 320 65 -100 6.48 0.4158
WVFGRD96 104.0 320 65 -100 6.49 0.4213
WVFGRD96 106.0 160 25 -70 6.50 0.4249
WVFGRD96 108.0 160 25 -70 6.50 0.4286
The best solution is
WVFGRD96 26.0 335 25 90 6.16 0.8480
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: