2014/04/11 01:08:03 -33.430 -72.104 25.0 5.1 Chile
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2014/04/11 01:08:03:0 -33.43 -72.10 25.0 5.1 Chile
Stations used:
C.GO04 C.GO05 G.PEL
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 = 1.27e+23 dyne-cm
Mw = 4.67
Z = 18 km
Plane Strike Dip Rake
NP1 151 76 95
NP2 310 15 70
Principal Axes:
Axis Value Plunge Azimuth
T 1.27e+23 59 68
N 0.00e+00 5 329
P -1.27e+23 31 236
Moment Tensor: (dyne-cm)
Component Value
Mxx -2.40e+22
Mxy -3.14e+22
Mxz 5.23e+22
Myy -3.58e+22
Myz 9.88e+22
Mzz 5.98e+22
--------------
#-##############------
#---###################-----
-----#####################----
--------######################----
---------########################---
-----------########################---
-------------########################---
--------------############ #########--
---------------############ T #########---
----------------########### ##########--
-----------------#######################--
------------------######################--
-------------------####################-
------ -----------###################-
----- P ------------#################-
---- -------------################
---------------------#############
--------------------##########
---------------------#######
--------------------##
--------------
Global CMT Convention Moment Tensor:
R T P
5.98e+22 5.23e+22 -9.88e+22
5.23e+22 -2.40e+22 3.14e+22
-9.88e+22 3.14e+22 -3.58e+22
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20140411010803/index.html
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STK = 310
DIP = 15
RAKE = 70
MW = 4.67
HS = 18.0
The NDK file is 20140411010803.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2014/04/11 01:08:03:0 -33.43 -72.10 25.0 5.1 Chile
Stations used:
C.GO04 C.GO05 G.PEL
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 = 1.27e+23 dyne-cm
Mw = 4.67
Z = 18 km
Plane Strike Dip Rake
NP1 151 76 95
NP2 310 15 70
Principal Axes:
Axis Value Plunge Azimuth
T 1.27e+23 59 68
N 0.00e+00 5 329
P -1.27e+23 31 236
Moment Tensor: (dyne-cm)
Component Value
Mxx -2.40e+22
Mxy -3.14e+22
Mxz 5.23e+22
Myy -3.58e+22
Myz 9.88e+22
Mzz 5.98e+22
--------------
#-##############------
#---###################-----
-----#####################----
--------######################----
---------########################---
-----------########################---
-------------########################---
--------------############ #########--
---------------############ T #########---
----------------########### ##########--
-----------------#######################--
------------------######################--
-------------------####################-
------ -----------###################-
----- P ------------#################-
---- -------------################
---------------------#############
--------------------##########
---------------------#######
--------------------##
--------------
Global CMT Convention Moment Tensor:
R T P
5.98e+22 5.23e+22 -9.88e+22
5.23e+22 -2.40e+22 3.14e+22
-9.88e+22 3.14e+22 -3.58e+22
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20140411010803/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 2.0 150 50 -90 4.46 0.4345
WVFGRD96 4.0 45 60 -10 4.58 0.3856
WVFGRD96 6.0 270 5 35 4.53 0.4422
WVFGRD96 8.0 290 5 55 4.61 0.5341
WVFGRD96 10.0 305 10 70 4.62 0.6261
WVFGRD96 12.0 300 15 65 4.64 0.6904
WVFGRD96 14.0 310 15 75 4.65 0.7326
WVFGRD96 16.0 290 20 55 4.67 0.7546
WVFGRD96 18.0 310 15 70 4.67 0.7605
WVFGRD96 20.0 305 15 65 4.68 0.7555
WVFGRD96 22.0 300 15 60 4.70 0.7432
WVFGRD96 24.0 295 10 55 4.72 0.7242
WVFGRD96 26.0 295 10 55 4.73 0.7001
WVFGRD96 28.0 270 10 30 4.74 0.6702
WVFGRD96 30.0 250 10 10 4.76 0.6353
WVFGRD96 32.0 250 10 10 4.76 0.5971
WVFGRD96 34.0 230 10 -10 4.77 0.5573
WVFGRD96 36.0 225 15 -15 4.78 0.5173
WVFGRD96 38.0 230 15 -10 4.77 0.4805
WVFGRD96 40.0 230 10 -10 4.92 0.4500
WVFGRD96 42.0 230 15 -10 4.91 0.3959
WVFGRD96 44.0 180 60 50 4.96 0.3491
WVFGRD96 46.0 180 60 50 4.96 0.3161
WVFGRD96 48.0 185 55 55 4.95 0.2876
WVFGRD96 50.0 -15 45 40 4.98 0.2680
WVFGRD96 52.0 -15 45 40 4.98 0.2511
WVFGRD96 54.0 150 90 -30 5.01 0.2427
WVFGRD96 56.0 150 90 -30 5.02 0.2481
WVFGRD96 58.0 340 75 40 5.01 0.2623
WVFGRD96 60.0 340 70 40 5.03 0.2727
WVFGRD96 62.0 340 70 40 5.04 0.2842
WVFGRD96 64.0 340 70 40 5.05 0.2772
WVFGRD96 66.0 345 65 45 5.05 0.2857
WVFGRD96 68.0 350 60 50 5.06 0.2955
WVFGRD96 70.0 355 55 55 5.06 0.2885
WVFGRD96 72.0 355 55 55 5.07 0.2989
WVFGRD96 74.0 355 55 55 5.08 0.3080
WVFGRD96 76.0 -5 55 55 5.08 0.2984
WVFGRD96 78.0 -10 55 50 5.09 0.3068
WVFGRD96 80.0 -10 55 50 5.10 0.3146
WVFGRD96 82.0 355 50 55 5.10 0.3046
WVFGRD96 84.0 355 50 55 5.10 0.3118
WVFGRD96 86.0 350 50 50 5.11 0.3037
WVFGRD96 88.0 350 50 50 5.11 0.3113
WVFGRD96 90.0 350 50 50 5.12 0.3180
WVFGRD96 92.0 350 50 50 5.11 0.3102
WVFGRD96 94.0 350 50 50 5.12 0.3168
WVFGRD96 96.0 175 45 -50 5.09 0.3203
WVFGRD96 98.0 175 45 -50 5.09 0.3255
WVFGRD96 100.0 175 45 -50 5.10 0.3324
WVFGRD96 102.0 180 50 -45 5.12 0.3388
WVFGRD96 104.0 180 50 -45 5.12 0.3427
WVFGRD96 106.0 180 50 -45 5.12 0.3478
WVFGRD96 108.0 180 50 -45 5.12 0.3509
The best solution is
WVFGRD96 18.0 310 15 70 4.67 0.7605
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: