2014/03/23 23:55:48 -19.962 -70.796 21.0 4.4 Chile
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2014/03/23 23:55:48:0 -19.96 -70.80 21.0 4.4 Chile
Stations used:
C.GO01 C.GO02 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 = 4.52e+22 dyne-cm
Mw = 4.37
Z = 20 km
Plane Strike Dip Rake
NP1 165 75 80
NP2 19 18 123
Principal Axes:
Axis Value Plunge Azimuth
T 4.52e+22 59 61
N 0.00e+00 10 168
P -4.52e+22 29 263
Moment Tensor: (dyne-cm)
Component Value
Mxx 2.30e+21
Mxy 1.00e+21
Mxz 1.19e+22
Myy -2.45e+22
Myz 3.67e+22
Mzz 2.22e+22
-#############
-----################-
--------##################--
---------###################--
-----------#####################--
------------######################--
-------------######################---
---------------########### ########---
---------------########### T ########---
----------------########### ########----
-----------------######################---
----- ---------#####################----
----- P ----------####################----
---- ----------####################---
------------------##################----
------------------################----
-----------------###############----
-----------------#############----
----------------##########----
----------------#######-----
--------------###-----
--------####--
Global CMT Convention Moment Tensor:
R T P
2.22e+22 1.19e+22 -3.67e+22
1.19e+22 2.30e+21 -1.00e+21
-3.67e+22 -1.00e+21 -2.45e+22
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20140323235548/index.html
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STK = 165
DIP = 75
RAKE = 80
MW = 4.37
HS = 20.0
The NDK file is 20140323235548.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2014/03/23 23:55:48:0 -19.96 -70.80 21.0 4.4 Chile
Stations used:
C.GO01 C.GO02 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 = 4.52e+22 dyne-cm
Mw = 4.37
Z = 20 km
Plane Strike Dip Rake
NP1 165 75 80
NP2 19 18 123
Principal Axes:
Axis Value Plunge Azimuth
T 4.52e+22 59 61
N 0.00e+00 10 168
P -4.52e+22 29 263
Moment Tensor: (dyne-cm)
Component Value
Mxx 2.30e+21
Mxy 1.00e+21
Mxz 1.19e+22
Myy -2.45e+22
Myz 3.67e+22
Mzz 2.22e+22
-#############
-----################-
--------##################--
---------###################--
-----------#####################--
------------######################--
-------------######################---
---------------########### ########---
---------------########### T ########---
----------------########### ########----
-----------------######################---
----- ---------#####################----
----- P ----------####################----
---- ----------####################---
------------------##################----
------------------################----
-----------------###############----
-----------------#############----
----------------##########----
----------------#######-----
--------------###-----
--------####--
Global CMT Convention Moment Tensor:
R T P
2.22e+22 1.19e+22 -3.67e+22
1.19e+22 2.30e+21 -1.00e+21
-3.67e+22 -1.00e+21 -2.45e+22
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20140323235548/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 2.0 165 45 -85 4.12 0.4396
WVFGRD96 4.0 305 70 45 4.14 0.3028
WVFGRD96 6.0 250 10 -10 4.19 0.4369
WVFGRD96 8.0 260 10 0 4.27 0.5283
WVFGRD96 10.0 165 85 80 4.28 0.6250
WVFGRD96 12.0 165 80 80 4.30 0.7013
WVFGRD96 14.0 165 75 80 4.32 0.7579
WVFGRD96 16.0 165 75 80 4.34 0.7958
WVFGRD96 18.0 165 75 80 4.35 0.8182
WVFGRD96 20.0 165 75 80 4.37 0.8275
WVFGRD96 22.0 160 75 80 4.39 0.8272
WVFGRD96 24.0 160 75 80 4.40 0.8185
WVFGRD96 26.0 160 75 80 4.41 0.8030
WVFGRD96 28.0 160 75 80 4.42 0.7818
WVFGRD96 30.0 160 75 80 4.43 0.7549
WVFGRD96 32.0 160 75 80 4.44 0.7236
WVFGRD96 34.0 160 75 85 4.44 0.6900
WVFGRD96 36.0 295 20 50 4.45 0.6547
WVFGRD96 38.0 295 20 50 4.45 0.6227
WVFGRD96 40.0 165 80 95 4.59 0.5943
WVFGRD96 42.0 350 15 100 4.59 0.5553
WVFGRD96 44.0 155 75 80 4.59 0.5195
WVFGRD96 46.0 155 70 80 4.60 0.4897
WVFGRD96 48.0 155 70 80 4.61 0.4625
WVFGRD96 50.0 155 70 80 4.61 0.4370
WVFGRD96 52.0 155 70 80 4.62 0.4145
WVFGRD96 54.0 155 70 80 4.62 0.3937
WVFGRD96 56.0 155 70 80 4.63 0.3746
WVFGRD96 58.0 340 75 75 4.62 0.3657
WVFGRD96 60.0 340 75 75 4.62 0.3626
WVFGRD96 62.0 340 70 75 4.63 0.3613
WVFGRD96 64.0 340 70 75 4.64 0.3607
WVFGRD96 66.0 340 70 75 4.64 0.3580
WVFGRD96 68.0 340 65 75 4.65 0.3570
WVFGRD96 70.0 340 65 75 4.65 0.3553
WVFGRD96 72.0 340 65 75 4.66 0.3527
WVFGRD96 74.0 340 60 75 4.66 0.3498
WVFGRD96 76.0 340 60 75 4.66 0.3484
WVFGRD96 78.0 340 60 75 4.67 0.3457
WVFGRD96 80.0 345 55 80 4.67 0.3443
WVFGRD96 82.0 340 55 75 4.67 0.3410
WVFGRD96 84.0 340 55 75 4.67 0.3407
WVFGRD96 86.0 335 55 75 4.68 0.3390
WVFGRD96 88.0 340 50 80 4.68 0.3359
WVFGRD96 90.0 340 50 80 4.68 0.3346
WVFGRD96 92.0 340 50 80 4.68 0.3315
WVFGRD96 94.0 340 50 80 4.68 0.3299
WVFGRD96 96.0 340 50 75 4.68 0.3288
WVFGRD96 98.0 155 30 -65 4.70 0.3304
WVFGRD96 100.0 155 30 -65 4.71 0.3385
WVFGRD96 102.0 155 35 -60 4.72 0.3440
WVFGRD96 104.0 155 35 -60 4.73 0.3518
WVFGRD96 106.0 155 35 -60 4.73 0.3583
WVFGRD96 108.0 155 35 -60 4.73 0.3625
The best solution is
WVFGRD96 20.0 165 75 80 4.37 0.8275
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: