2014/03/23 21:17:27 -19.709 -70.554 21.7 4.7 Chile
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2014/03/23 21:17:27:0 -19.71 -70.55 21.7 4.7 Chile
Stations used:
C.GO01 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 = 8.41e+22 dyne-cm
Mw = 4.55
Z = 24 km
Plane Strike Dip Rake
NP1 155 75 93
NP2 325 15 80
Principal Axes:
Axis Value Plunge Azimuth
T 8.41e+22 60 69
N 0.00e+00 3 335
P -8.41e+22 30 243
Moment Tensor: (dyne-cm)
Component Value
Mxx -1.01e+22
Mxy -1.82e+22
Mxz 2.96e+22
Myy -3.14e+22
Myz 6.69e+22
Mzz 4.14e+22
--------------
--###############-----
-----##################-----
-------###################----
---------#####################----
----------#######################---
------------#######################---
-------------########################---
--------------############ ########---
----------------########### T #########---
----------------########### #########---
-----------------######################---
------------------#####################---
----- ----------####################--
----- P -----------###################--
---- ------------#################--
-------------------################-
-------------------##############-
-------------------###########
-------------------########-
------------------####
--------------
Global CMT Convention Moment Tensor:
R T P
4.14e+22 2.96e+22 -6.69e+22
2.96e+22 -1.01e+22 1.82e+22
-6.69e+22 1.82e+22 -3.14e+22
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20140323211727/index.html
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STK = 325
DIP = 15
RAKE = 80
MW = 4.55
HS = 24.0
The NDK file is 20140323211727.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2014/03/23 21:17:27:0 -19.71 -70.55 21.7 4.7 Chile
Stations used:
C.GO01 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 = 8.41e+22 dyne-cm
Mw = 4.55
Z = 24 km
Plane Strike Dip Rake
NP1 155 75 93
NP2 325 15 80
Principal Axes:
Axis Value Plunge Azimuth
T 8.41e+22 60 69
N 0.00e+00 3 335
P -8.41e+22 30 243
Moment Tensor: (dyne-cm)
Component Value
Mxx -1.01e+22
Mxy -1.82e+22
Mxz 2.96e+22
Myy -3.14e+22
Myz 6.69e+22
Mzz 4.14e+22
--------------
--###############-----
-----##################-----
-------###################----
---------#####################----
----------#######################---
------------#######################---
-------------########################---
--------------############ ########---
----------------########### T #########---
----------------########### #########---
-----------------######################---
------------------#####################---
----- ----------####################--
----- P -----------###################--
---- ------------#################--
-------------------################-
-------------------##############-
-------------------###########
-------------------########-
------------------####
--------------
Global CMT Convention Moment Tensor:
R T P
4.14e+22 2.96e+22 -6.69e+22
2.96e+22 -1.01e+22 1.82e+22
-6.69e+22 1.82e+22 -3.14e+22
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20140323211727/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 2.0 355 45 90 4.27 0.3667
WVFGRD96 4.0 130 90 30 4.28 0.3088
WVFGRD96 6.0 150 85 75 4.35 0.3970
WVFGRD96 8.0 150 85 75 4.43 0.4955
WVFGRD96 10.0 155 80 75 4.45 0.6024
WVFGRD96 12.0 160 75 75 4.46 0.6839
WVFGRD96 14.0 160 75 75 4.48 0.7438
WVFGRD96 16.0 165 70 80 4.50 0.7860
WVFGRD96 18.0 325 20 75 4.51 0.8139
WVFGRD96 20.0 325 20 75 4.52 0.8323
WVFGRD96 22.0 325 15 80 4.54 0.8391
WVFGRD96 24.0 325 15 80 4.55 0.8399
WVFGRD96 26.0 325 15 80 4.57 0.8341
WVFGRD96 28.0 325 15 80 4.58 0.8213
WVFGRD96 30.0 325 15 80 4.59 0.8033
WVFGRD96 32.0 325 15 80 4.60 0.7810
WVFGRD96 34.0 330 15 85 4.61 0.7556
WVFGRD96 36.0 335 15 90 4.62 0.7295
WVFGRD96 38.0 155 75 90 4.62 0.7044
WVFGRD96 40.0 155 80 90 4.76 0.6774
WVFGRD96 42.0 155 80 90 4.77 0.6526
WVFGRD96 44.0 155 75 85 4.79 0.6276
WVFGRD96 46.0 335 10 90 4.79 0.6029
WVFGRD96 48.0 330 10 85 4.79 0.5785
WVFGRD96 50.0 155 90 95 4.79 0.5563
WVFGRD96 52.0 215 5 -25 4.80 0.5357
WVFGRD96 54.0 230 10 -15 4.80 0.5161
WVFGRD96 56.0 200 10 -40 4.81 0.4974
WVFGRD96 58.0 160 10 -75 4.82 0.4812
WVFGRD96 60.0 160 10 -75 4.82 0.4673
WVFGRD96 62.0 160 10 -75 4.83 0.4532
WVFGRD96 64.0 160 15 -75 4.83 0.4392
WVFGRD96 66.0 170 15 -65 4.84 0.4272
WVFGRD96 68.0 160 20 -70 4.84 0.4152
WVFGRD96 70.0 160 20 -70 4.84 0.4043
WVFGRD96 72.0 160 20 -70 4.85 0.3933
WVFGRD96 74.0 165 25 -65 4.85 0.3839
WVFGRD96 76.0 175 30 -60 4.86 0.3852
WVFGRD96 78.0 175 30 -60 4.86 0.3877
WVFGRD96 80.0 170 30 -60 4.87 0.3895
WVFGRD96 82.0 170 30 -60 4.88 0.3904
WVFGRD96 84.0 175 35 -60 4.88 0.3915
WVFGRD96 86.0 175 35 -60 4.88 0.3920
WVFGRD96 88.0 175 35 -60 4.88 0.3926
WVFGRD96 90.0 175 35 -60 4.89 0.3923
WVFGRD96 92.0 165 35 -75 4.88 0.3922
WVFGRD96 94.0 165 35 -75 4.88 0.3937
WVFGRD96 96.0 165 35 -75 4.89 0.3951
WVFGRD96 98.0 165 35 -75 4.89 0.3959
WVFGRD96 100.0 165 35 -75 4.90 0.3957
WVFGRD96 102.0 165 35 -75 4.90 0.3955
WVFGRD96 104.0 170 40 -70 4.90 0.3983
WVFGRD96 106.0 170 40 -70 4.90 0.3998
WVFGRD96 108.0 170 40 -70 4.91 0.4055
The best solution is
WVFGRD96 24.0 325 15 80 4.55 0.8399
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: