2014/04/15 17:12:19 -20.179 -70.781 15.8 4.7 Chile
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2014/04/15 17:12:19:0 -20.18 -70.78 15.8 4.7 Chile
Stations used:
C.GO01 C.GO02 CX.MNMCX CX.PATCX CX.PB01 CX.PB04 CX.PB06
CX.PB07 CX.PB08 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 = 1.62e+23 dyne-cm
Mw = 4.74
Z = 18 km
Plane Strike Dip Rake
NP1 170 65 90
NP2 350 25 90
Principal Axes:
Axis Value Plunge Azimuth
T 1.62e+23 70 80
N 0.00e+00 -0 170
P -1.62e+23 20 260
Moment Tensor: (dyne-cm)
Component Value
Mxx -3.75e+21
Mxy -2.12e+22
Mxz 1.81e+22
Myy -1.20e+23
Myz 1.03e+23
Mzz 1.24e+23
---######-----
------###########-----
--------##############------
---------################-----
----------###################-----
-----------####################-----
------------#####################-----
-------------######################-----
-------------######################-----
--------------########### #########-----
--------------########### T #########-----
--- ---------########## #########-----
--- P ---------######################-----
-- ----------#####################----
---------------####################-----
---------------###################----
--------------##################----
--------------################----
-------------##############---
-------------###########----
------------#######---
---------####-
Global CMT Convention Moment Tensor:
R T P
1.24e+23 1.81e+22 -1.03e+23
1.81e+22 -3.75e+21 2.12e+22
-1.03e+23 2.12e+22 -1.20e+23
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20140415171219/index.html
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STK = 170
DIP = 65
RAKE = 90
MW = 4.74
HS = 18.0
The NDK file is 20140415171219.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2014/04/15 17:12:19:0 -20.18 -70.78 15.8 4.7 Chile
Stations used:
C.GO01 C.GO02 CX.MNMCX CX.PATCX CX.PB01 CX.PB04 CX.PB06
CX.PB07 CX.PB08 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 = 1.62e+23 dyne-cm
Mw = 4.74
Z = 18 km
Plane Strike Dip Rake
NP1 170 65 90
NP2 350 25 90
Principal Axes:
Axis Value Plunge Azimuth
T 1.62e+23 70 80
N 0.00e+00 -0 170
P -1.62e+23 20 260
Moment Tensor: (dyne-cm)
Component Value
Mxx -3.75e+21
Mxy -2.12e+22
Mxz 1.81e+22
Myy -1.20e+23
Myz 1.03e+23
Mzz 1.24e+23
---######-----
------###########-----
--------##############------
---------################-----
----------###################-----
-----------####################-----
------------#####################-----
-------------######################-----
-------------######################-----
--------------########### #########-----
--------------########### T #########-----
--- ---------########## #########-----
--- P ---------######################-----
-- ----------#####################----
---------------####################-----
---------------###################----
--------------##################----
--------------################----
-------------##############---
-------------###########----
------------#######---
---------####-
Global CMT Convention Moment Tensor:
R T P
1.24e+23 1.81e+22 -1.03e+23
1.81e+22 -3.75e+21 2.12e+22
-1.03e+23 2.12e+22 -1.20e+23
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20140415171219/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 2.0 155 45 -90 4.47 0.3841
WVFGRD96 4.0 170 90 80 4.58 0.3172
WVFGRD96 6.0 350 90 -85 4.58 0.4667
WVFGRD96 8.0 170 85 85 4.66 0.5583
WVFGRD96 10.0 170 75 90 4.68 0.6492
WVFGRD96 12.0 170 70 90 4.70 0.7221
WVFGRD96 14.0 170 70 90 4.71 0.7745
WVFGRD96 16.0 170 65 90 4.73 0.8024
WVFGRD96 18.0 170 65 90 4.74 0.8131
WVFGRD96 20.0 170 65 90 4.74 0.8088
WVFGRD96 22.0 350 25 90 4.76 0.7955
WVFGRD96 24.0 355 25 95 4.77 0.7732
WVFGRD96 26.0 365 20 105 4.78 0.7457
WVFGRD96 28.0 170 70 85 4.78 0.7133
WVFGRD96 30.0 170 70 85 4.79 0.6765
WVFGRD96 32.0 170 70 85 4.79 0.6364
WVFGRD96 34.0 170 70 85 4.80 0.5944
WVFGRD96 36.0 170 70 85 4.80 0.5527
WVFGRD96 38.0 170 70 85 4.80 0.5136
WVFGRD96 40.0 170 80 85 4.94 0.4834
WVFGRD96 42.0 170 75 85 4.93 0.4423
WVFGRD96 44.0 370 15 110 4.93 0.4047
WVFGRD96 46.0 170 75 85 4.93 0.3712
WVFGRD96 48.0 170 70 85 4.93 0.3416
WVFGRD96 50.0 365 20 105 4.94 0.3152
WVFGRD96 52.0 145 60 60 4.94 0.2928
WVFGRD96 54.0 145 60 60 4.94 0.2766
WVFGRD96 56.0 150 60 65 4.94 0.2620
WVFGRD96 58.0 125 70 50 4.95 0.2501
WVFGRD96 60.0 130 70 50 4.94 0.2392
WVFGRD96 62.0 120 50 25 4.97 0.2327
WVFGRD96 64.0 125 50 35 4.97 0.2296
WVFGRD96 66.0 130 50 40 4.97 0.2286
WVFGRD96 68.0 130 50 40 4.98 0.2306
WVFGRD96 70.0 135 50 50 4.98 0.2278
WVFGRD96 72.0 135 50 50 4.99 0.2313
WVFGRD96 74.0 130 55 45 4.99 0.2303
WVFGRD96 76.0 135 55 50 5.00 0.2326
WVFGRD96 78.0 135 55 50 5.00 0.2332
WVFGRD96 80.0 140 55 60 5.01 0.2340
WVFGRD96 82.0 135 55 50 5.01 0.2346
WVFGRD96 84.0 140 55 55 5.01 0.2361
WVFGRD96 86.0 140 55 55 5.01 0.2360
WVFGRD96 88.0 140 55 55 5.01 0.2347
WVFGRD96 90.0 150 45 55 5.01 0.2413
WVFGRD96 92.0 150 50 60 5.01 0.2409
WVFGRD96 94.0 150 50 60 5.02 0.2453
WVFGRD96 96.0 155 50 65 5.02 0.2509
WVFGRD96 98.0 155 50 65 5.02 0.2536
WVFGRD96 100.0 155 50 65 5.03 0.2579
WVFGRD96 102.0 165 45 75 5.02 0.2601
WVFGRD96 104.0 165 45 75 5.02 0.2611
WVFGRD96 106.0 165 50 80 5.03 0.2654
WVFGRD96 108.0 165 50 80 5.03 0.2701
The best solution is
WVFGRD96 18.0 170 65 90 4.74 0.8131
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: