2014/04/07 06:24:22 -20.700 -70.947 14.2 4.9 Chile
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2014/04/07 06:24:22:0 -20.70 -70.95 14.2 4.9 Chile
Stations used:
CX.MNMCX CX.PATCX CX.PB01 CX.PB04 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 = 1.23e+23 dyne-cm
Mw = 4.66
Z = 18 km
Plane Strike Dip Rake
NP1 164 65 88
NP2 350 25 95
Principal Axes:
Axis Value Plunge Azimuth
T 1.23e+23 70 70
N 0.00e+00 2 165
P -1.23e+23 20 256
Moment Tensor: (dyne-cm)
Component Value
Mxx -4.38e+21
Mxy -2.03e+22
Mxz 2.33e+22
Myy -8.95e+22
Myz 7.59e+22
Mzz 9.39e+22
-########-----
----#############-----
-------###############------
--------#################-----
---------####################-----
----------#####################-----
-----------######################-----
------------#######################-----
-------------######################-----
--------------######## ############-----
--------------######## T ############-----
---------------####### ############-----
--- ---------######################-----
-- P ----------#####################----
-- -----------###################-----
---------------###################----
---------------#################----
---------------###############----
--------------#############---
---------------#########----
-------------######---
------------#-
Global CMT Convention Moment Tensor:
R T P
9.39e+22 2.33e+22 -7.59e+22
2.33e+22 -4.38e+21 2.03e+22
-7.59e+22 2.03e+22 -8.95e+22
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20140407062422/index.html
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STK = 350
DIP = 25
RAKE = 95
MW = 4.66
HS = 18.0
The NDK file is 20140407062422.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2014/04/07 06:24:22:0 -20.70 -70.95 14.2 4.9 Chile
Stations used:
CX.MNMCX CX.PATCX CX.PB01 CX.PB04 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 = 1.23e+23 dyne-cm
Mw = 4.66
Z = 18 km
Plane Strike Dip Rake
NP1 164 65 88
NP2 350 25 95
Principal Axes:
Axis Value Plunge Azimuth
T 1.23e+23 70 70
N 0.00e+00 2 165
P -1.23e+23 20 256
Moment Tensor: (dyne-cm)
Component Value
Mxx -4.38e+21
Mxy -2.03e+22
Mxz 2.33e+22
Myy -8.95e+22
Myz 7.59e+22
Mzz 9.39e+22
-########-----
----#############-----
-------###############------
--------#################-----
---------####################-----
----------#####################-----
-----------######################-----
------------#######################-----
-------------######################-----
--------------######## ############-----
--------------######## T ############-----
---------------####### ############-----
--- ---------######################-----
-- P ----------#####################----
-- -----------###################-----
---------------###################----
---------------#################----
---------------###############----
--------------#############---
---------------#########----
-------------######---
------------#-
Global CMT Convention Moment Tensor:
R T P
9.39e+22 2.33e+22 -7.59e+22
2.33e+22 -4.38e+21 2.03e+22
-7.59e+22 2.03e+22 -8.95e+22
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20140407062422/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 2.0 350 50 -90 4.40 0.4023
WVFGRD96 4.0 345 85 -75 4.51 0.3475
WVFGRD96 6.0 345 85 -75 4.51 0.4950
WVFGRD96 8.0 345 85 -80 4.59 0.5798
WVFGRD96 10.0 165 90 75 4.59 0.6506
WVFGRD96 12.0 345 20 90 4.62 0.7078
WVFGRD96 14.0 350 25 95 4.64 0.7548
WVFGRD96 16.0 350 25 95 4.65 0.7815
WVFGRD96 18.0 350 25 95 4.66 0.7873
WVFGRD96 20.0 165 65 90 4.66 0.7793
WVFGRD96 22.0 350 25 95 4.68 0.7640
WVFGRD96 24.0 345 25 90 4.68 0.7411
WVFGRD96 26.0 345 25 90 4.69 0.7153
WVFGRD96 28.0 345 25 90 4.70 0.6878
WVFGRD96 30.0 155 65 70 4.72 0.6618
WVFGRD96 32.0 155 65 70 4.73 0.6309
WVFGRD96 34.0 155 65 70 4.73 0.5978
WVFGRD96 36.0 155 70 65 4.75 0.5637
WVFGRD96 38.0 155 70 65 4.75 0.5300
WVFGRD96 40.0 160 70 80 4.87 0.5090
WVFGRD96 42.0 155 70 75 4.88 0.4761
WVFGRD96 44.0 155 70 75 4.88 0.4435
WVFGRD96 46.0 155 70 70 4.89 0.4121
WVFGRD96 48.0 155 70 70 4.89 0.3816
WVFGRD96 50.0 160 70 80 4.89 0.3532
WVFGRD96 52.0 310 35 35 4.89 0.3279
WVFGRD96 54.0 305 40 25 4.89 0.3071
WVFGRD96 56.0 305 40 25 4.90 0.2896
WVFGRD96 58.0 305 40 25 4.90 0.2730
WVFGRD96 60.0 300 40 20 4.90 0.2595
WVFGRD96 62.0 130 30 40 4.88 0.2601
WVFGRD96 64.0 130 30 40 4.89 0.2653
WVFGRD96 66.0 135 30 45 4.90 0.2679
WVFGRD96 68.0 140 30 50 4.91 0.2739
WVFGRD96 70.0 145 30 55 4.91 0.2791
WVFGRD96 72.0 145 35 55 4.92 0.2845
WVFGRD96 74.0 145 35 55 4.93 0.2874
WVFGRD96 76.0 145 35 55 4.93 0.2915
WVFGRD96 78.0 150 35 60 4.94 0.2946
WVFGRD96 80.0 150 35 60 4.94 0.2950
WVFGRD96 82.0 150 35 60 4.95 0.2993
WVFGRD96 84.0 150 35 60 4.95 0.3003
WVFGRD96 86.0 150 40 60 4.95 0.3028
WVFGRD96 88.0 150 40 60 4.96 0.3065
WVFGRD96 90.0 150 40 60 4.96 0.3072
WVFGRD96 92.0 150 40 60 4.96 0.3086
WVFGRD96 94.0 150 40 60 4.97 0.3106
WVFGRD96 96.0 0 50 -80 4.97 0.3093
WVFGRD96 98.0 0 50 -80 4.97 0.3159
WVFGRD96 100.0 0 50 -80 4.98 0.3203
WVFGRD96 102.0 0 50 -80 4.98 0.3238
WVFGRD96 104.0 -5 45 -85 4.99 0.3298
WVFGRD96 106.0 -5 45 -85 4.99 0.3337
WVFGRD96 108.0 -5 45 -85 4.99 0.3360
The best solution is
WVFGRD96 18.0 350 25 95 4.66 0.7873
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: