2014/03/23 20:07:12 -19.745 -70.976 24.6 4.7 Chile
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2014/03/23 20:07:12:0 -19.75 -70.98 24.6 4.7 Chile
Stations used:
C.GO01 CX.PATCX CX.PB01 CX.PB04 CX.PB07 CX.PB09 CX.PB10
CX.PB11 CX.PB12 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 = 4.37e+22 dyne-cm
Mw = 4.36
Z = 20 km
Plane Strike Dip Rake
NP1 165 65 80
NP2 8 27 110
Principal Axes:
Axis Value Plunge Azimuth
T 4.37e+22 68 55
N 0.00e+00 9 169
P -4.37e+22 19 262
Moment Tensor: (dyne-cm)
Component Value
Mxx 1.23e+21
Mxy -2.28e+21
Mxz 1.02e+22
Myy -3.42e+22
Myz 2.59e+22
Mzz 3.29e+22
-###########--
-----##############---
-------#################----
--------##################----
---------#####################----
----------#####################-----
-----------######################-----
------------#######################-----
-------------########## #########-----
--------------########## T #########------
--------------########## #########------
--- ---------#####################------
--- P ---------#####################------
-- ----------####################-----
---------------###################------
---------------#################------
---------------################-----
---------------#############------
--------------###########-----
---------------#######------
-------------####-----
---------##---
Global CMT Convention Moment Tensor:
R T P
3.29e+22 1.02e+22 -2.59e+22
1.02e+22 1.23e+21 2.28e+21
-2.59e+22 2.28e+21 -3.42e+22
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20140323200712/index.html
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STK = 165
DIP = 65
RAKE = 80
MW = 4.36
HS = 20.0
The NDK file is 20140323200712.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2014/03/23 20:07:12:0 -19.75 -70.98 24.6 4.7 Chile
Stations used:
C.GO01 CX.PATCX CX.PB01 CX.PB04 CX.PB07 CX.PB09 CX.PB10
CX.PB11 CX.PB12 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 = 4.37e+22 dyne-cm
Mw = 4.36
Z = 20 km
Plane Strike Dip Rake
NP1 165 65 80
NP2 8 27 110
Principal Axes:
Axis Value Plunge Azimuth
T 4.37e+22 68 55
N 0.00e+00 9 169
P -4.37e+22 19 262
Moment Tensor: (dyne-cm)
Component Value
Mxx 1.23e+21
Mxy -2.28e+21
Mxz 1.02e+22
Myy -3.42e+22
Myz 2.59e+22
Mzz 3.29e+22
-###########--
-----##############---
-------#################----
--------##################----
---------#####################----
----------#####################-----
-----------######################-----
------------#######################-----
-------------########## #########-----
--------------########## T #########------
--------------########## #########------
--- ---------#####################------
--- P ---------#####################------
-- ----------####################-----
---------------###################------
---------------#################------
---------------################-----
---------------#############------
--------------###########-----
---------------#######------
-------------####-----
---------##---
Global CMT Convention Moment Tensor:
R T P
3.29e+22 1.02e+22 -2.59e+22
1.02e+22 1.23e+21 2.28e+21
-2.59e+22 2.28e+21 -3.42e+22
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20140323200712/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 -5 50 -90 4.10 0.3971
WVFGRD96 4.0 220 10 -45 4.19 0.2963
WVFGRD96 6.0 235 10 -25 4.19 0.4329
WVFGRD96 8.0 235 10 -25 4.27 0.5165
WVFGRD96 10.0 240 10 -20 4.27 0.5946
WVFGRD96 12.0 280 10 20 4.28 0.6453
WVFGRD96 14.0 165 75 80 4.30 0.6872
WVFGRD96 16.0 165 70 80 4.33 0.7231
WVFGRD96 18.0 160 65 90 4.35 0.7455
WVFGRD96 20.0 165 65 80 4.36 0.7538
WVFGRD96 22.0 160 65 90 4.38 0.7513
WVFGRD96 24.0 160 65 75 4.39 0.7416
WVFGRD96 26.0 160 65 75 4.40 0.7265
WVFGRD96 28.0 345 30 95 4.41 0.7071
WVFGRD96 30.0 160 65 75 4.41 0.6841
WVFGRD96 32.0 360 30 110 4.42 0.6563
WVFGRD96 34.0 340 25 90 4.43 0.6256
WVFGRD96 36.0 340 25 90 4.44 0.5926
WVFGRD96 38.0 335 25 85 4.45 0.5602
WVFGRD96 40.0 165 70 95 4.57 0.5298
WVFGRD96 42.0 335 25 80 4.58 0.4981
WVFGRD96 44.0 335 25 80 4.58 0.4666
WVFGRD96 46.0 165 65 95 4.59 0.4351
WVFGRD96 48.0 165 65 75 4.59 0.4051
WVFGRD96 50.0 165 70 75 4.59 0.3779
WVFGRD96 52.0 165 70 75 4.59 0.3531
WVFGRD96 54.0 165 70 75 4.60 0.3298
WVFGRD96 56.0 160 70 70 4.60 0.3124
WVFGRD96 58.0 160 70 70 4.61 0.2960
WVFGRD96 60.0 160 70 65 4.62 0.2809
WVFGRD96 62.0 60 25 -5 4.60 0.2788
WVFGRD96 64.0 340 75 75 4.61 0.2831
WVFGRD96 66.0 335 75 75 4.62 0.2856
WVFGRD96 68.0 340 70 75 4.62 0.2901
WVFGRD96 70.0 340 70 75 4.63 0.2953
WVFGRD96 72.0 340 70 75 4.64 0.3006
WVFGRD96 74.0 340 70 75 4.64 0.3055
WVFGRD96 76.0 340 65 75 4.65 0.3062
WVFGRD96 78.0 340 65 75 4.65 0.3107
WVFGRD96 80.0 340 65 75 4.66 0.3142
WVFGRD96 82.0 340 65 75 4.66 0.3171
WVFGRD96 84.0 340 65 75 4.66 0.3153
WVFGRD96 86.0 345 60 75 4.66 0.3197
WVFGRD96 88.0 345 60 75 4.67 0.3223
WVFGRD96 90.0 345 60 75 4.67 0.3231
WVFGRD96 92.0 340 60 75 4.67 0.3259
WVFGRD96 94.0 340 65 75 4.68 0.3291
WVFGRD96 96.0 335 65 95 4.69 0.3300
WVFGRD96 98.0 345 60 75 4.68 0.3340
WVFGRD96 100.0 340 60 75 4.69 0.3341
WVFGRD96 102.0 340 60 75 4.69 0.3376
WVFGRD96 104.0 180 40 -75 4.69 0.3404
WVFGRD96 106.0 180 40 -75 4.69 0.3437
WVFGRD96 108.0 180 40 -75 4.70 0.3491
The best solution is
WVFGRD96 20.0 165 65 80 4.36 0.7538
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: