2014/04/05 19:21:43 -20.750 -70.664 16.2 4.6 Chile
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2014/04/05 19:21:43:0 -20.75 -70.66 16.2 4.6 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 = 2.69e+22 dyne-cm
Mw = 4.22
Z = 20 km
Plane Strike Dip Rake
NP1 130 65 70
NP2 351 32 126
Principal Axes:
Axis Value Plunge Azimuth
T 2.69e+22 64 6
N 0.00e+00 18 139
P -2.69e+22 18 235
Moment Tensor: (dyne-cm)
Component Value
Mxx -3.15e+21
Mxy -1.10e+22
Mxz 1.50e+22
Myy -1.62e+22
Myz 7.47e+21
Mzz 1.94e+22
########------
###############-------
#####################-------
########################------
-##########################-------
---##########################-------
-----############# ##########-------
------############# T ###########-------
-------############ ############------
----------#########################-------
-----------########################-------
-------------######################-------
---------------####################-------
----------------##################------
------------------################------
--- --------------############------
-- P -----------------#########-----
- ---------------------####-----
--------------------------####
-----------------------#####
-------------------###
------------##
Global CMT Convention Moment Tensor:
R T P
1.94e+22 1.50e+22 -7.47e+21
1.50e+22 -3.15e+21 1.10e+22
-7.47e+21 1.10e+22 -1.62e+22
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20140405192143/index.html
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STK = 130
DIP = 65
RAKE = 70
MW = 4.22
HS = 20.0
The NDK file is 20140405192143.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2014/04/05 19:21:43:0 -20.75 -70.66 16.2 4.6 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 = 2.69e+22 dyne-cm
Mw = 4.22
Z = 20 km
Plane Strike Dip Rake
NP1 130 65 70
NP2 351 32 126
Principal Axes:
Axis Value Plunge Azimuth
T 2.69e+22 64 6
N 0.00e+00 18 139
P -2.69e+22 18 235
Moment Tensor: (dyne-cm)
Component Value
Mxx -3.15e+21
Mxy -1.10e+22
Mxz 1.50e+22
Myy -1.62e+22
Myz 7.47e+21
Mzz 1.94e+22
########------
###############-------
#####################-------
########################------
-##########################-------
---##########################-------
-----############# ##########-------
------############# T ###########-------
-------############ ############------
----------#########################-------
-----------########################-------
-------------######################-------
---------------####################-------
----------------##################------
------------------################------
--- --------------############------
-- P -----------------#########-----
- ---------------------####-----
--------------------------####
-----------------------#####
-------------------###
------------##
Global CMT Convention Moment Tensor:
R T P
1.94e+22 1.50e+22 -7.47e+21
1.50e+22 -3.15e+21 1.10e+22
-7.47e+21 1.10e+22 -1.62e+22
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20140405192143/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 2.0 140 40 90 3.95 0.3775
WVFGRD96 4.0 310 60 80 4.01 0.2816
WVFGRD96 6.0 300 90 -65 4.03 0.3784
WVFGRD96 8.0 300 90 -70 4.11 0.4496
WVFGRD96 10.0 125 80 70 4.13 0.5260
WVFGRD96 12.0 130 70 70 4.15 0.5905
WVFGRD96 14.0 130 65 70 4.18 0.6445
WVFGRD96 16.0 130 65 70 4.19 0.6820
WVFGRD96 18.0 130 65 70 4.20 0.7028
WVFGRD96 20.0 130 65 70 4.22 0.7111
WVFGRD96 22.0 130 65 70 4.23 0.7097
WVFGRD96 24.0 130 70 70 4.24 0.7011
WVFGRD96 26.0 130 70 70 4.25 0.6880
WVFGRD96 28.0 130 70 70 4.26 0.6701
WVFGRD96 30.0 130 70 70 4.27 0.6463
WVFGRD96 32.0 130 70 70 4.28 0.6182
WVFGRD96 34.0 130 70 70 4.29 0.5874
WVFGRD96 36.0 130 75 70 4.29 0.5570
WVFGRD96 38.0 130 75 70 4.30 0.5281
WVFGRD96 40.0 130 80 75 4.43 0.5006
WVFGRD96 42.0 135 75 75 4.43 0.4703
WVFGRD96 44.0 135 75 75 4.43 0.4394
WVFGRD96 46.0 135 75 75 4.43 0.4094
WVFGRD96 48.0 135 75 70 4.43 0.3808
WVFGRD96 50.0 135 75 70 4.43 0.3550
WVFGRD96 52.0 135 75 70 4.43 0.3314
WVFGRD96 54.0 80 40 -85 4.45 0.3129
WVFGRD96 56.0 85 40 -75 4.47 0.3034
WVFGRD96 58.0 90 40 -70 4.47 0.2953
WVFGRD96 60.0 90 40 -70 4.48 0.2872
WVFGRD96 62.0 90 40 -70 4.48 0.2793
WVFGRD96 64.0 90 40 -65 4.49 0.2734
WVFGRD96 66.0 80 45 -70 4.49 0.2680
WVFGRD96 68.0 90 30 -75 4.49 0.2687
WVFGRD96 70.0 85 30 -80 4.49 0.2706
WVFGRD96 72.0 90 30 -75 4.50 0.2735
WVFGRD96 74.0 90 30 -80 4.50 0.2749
WVFGRD96 76.0 90 30 -80 4.50 0.2765
WVFGRD96 78.0 90 30 -80 4.51 0.2780
WVFGRD96 80.0 265 55 -85 4.49 0.2805
WVFGRD96 82.0 265 55 -85 4.50 0.2824
WVFGRD96 84.0 275 60 -80 4.49 0.2844
WVFGRD96 86.0 270 60 -85 4.50 0.2865
WVFGRD96 88.0 270 60 -85 4.51 0.2888
WVFGRD96 90.0 270 60 -85 4.51 0.2902
WVFGRD96 92.0 270 60 -85 4.51 0.2913
WVFGRD96 94.0 270 60 -85 4.52 0.2930
WVFGRD96 96.0 270 60 -85 4.52 0.2936
WVFGRD96 98.0 270 60 -85 4.52 0.2955
WVFGRD96 100.0 270 60 -85 4.52 0.2958
WVFGRD96 102.0 270 60 -85 4.53 0.2973
WVFGRD96 104.0 270 60 -85 4.53 0.2972
WVFGRD96 106.0 270 60 -85 4.53 0.2968
WVFGRD96 108.0 265 60 -85 4.53 0.2990
The best solution is
WVFGRD96 20.0 130 65 70 4.22 0.7111
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: