2014/03/24 15:11:44 -19.603 -70.807 26.4 4.5 Chile
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2014/03/24 15:11:44:0 -19.60 -70.81 26.4 4.5 Chile
Stations used:
C.GO01 CX.PATCX CX.PB01 CX.PB09 CX.PB11 CX.PB12 CX.PB16
CX.PSGCX GT.LPAZ
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 = 1.35e+22 dyne-cm
Mw = 4.02
Z = 24 km
Plane Strike Dip Rake
NP1 145 70 80
NP2 352 22 116
Principal Axes:
Axis Value Plunge Azimuth
T 1.35e+22 64 39
N 0.00e+00 9 148
P -1.35e+22 24 243
Moment Tensor: (dyne-cm)
Component Value
Mxx -7.41e+20
Mxy -3.26e+21
Mxz 6.49e+21
Myy -7.80e+21
Myz 7.88e+21
Mzz 8.54e+21
##########----
#################-----
--#####################-----
---#######################----
------#######################-----
-------#########################----
---------########################-----
-----------########### ##########-----
-----------########### T ###########----
-------------########## ###########-----
--------------#######################-----
---------------######################-----
-----------------####################-----
---- ----------###################----
---- P ------------#################----
--- -------------###############----
--------------------############----
---------------------#########----
---------------------######---
-----------------------#----
-------------------###
------------##
Global CMT Convention Moment Tensor:
R T P
8.54e+21 6.49e+21 -7.88e+21
6.49e+21 -7.41e+20 3.26e+21
-7.88e+21 3.26e+21 -7.80e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20140324151144/index.html
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STK = 145
DIP = 70
RAKE = 80
MW = 4.02
HS = 24.0
The NDK file is 20140324151144.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2014/03/24 15:11:44:0 -19.60 -70.81 26.4 4.5 Chile
Stations used:
C.GO01 CX.PATCX CX.PB01 CX.PB09 CX.PB11 CX.PB12 CX.PB16
CX.PSGCX GT.LPAZ
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 = 1.35e+22 dyne-cm
Mw = 4.02
Z = 24 km
Plane Strike Dip Rake
NP1 145 70 80
NP2 352 22 116
Principal Axes:
Axis Value Plunge Azimuth
T 1.35e+22 64 39
N 0.00e+00 9 148
P -1.35e+22 24 243
Moment Tensor: (dyne-cm)
Component Value
Mxx -7.41e+20
Mxy -3.26e+21
Mxz 6.49e+21
Myy -7.80e+21
Myz 7.88e+21
Mzz 8.54e+21
##########----
#################-----
--#####################-----
---#######################----
------#######################-----
-------#########################----
---------########################-----
-----------########### ##########-----
-----------########### T ###########----
-------------########## ###########-----
--------------#######################-----
---------------######################-----
-----------------####################-----
---- ----------###################----
---- P ------------#################----
--- -------------###############----
--------------------############----
---------------------#########----
---------------------######---
-----------------------#----
-------------------###
------------##
Global CMT Convention Moment Tensor:
R T P
8.54e+21 6.49e+21 -7.88e+21
6.49e+21 -7.41e+20 3.26e+21
-7.88e+21 3.26e+21 -7.80e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20140324151144/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 2.0 160 40 90 3.72 0.3903
WVFGRD96 4.0 325 85 -65 3.77 0.2843
WVFGRD96 6.0 325 85 -75 3.80 0.4226
WVFGRD96 8.0 325 85 -75 3.88 0.5120
WVFGRD96 10.0 325 85 -75 3.89 0.6041
WVFGRD96 12.0 150 75 85 3.91 0.6708
WVFGRD96 14.0 150 70 85 3.94 0.7353
WVFGRD96 16.0 145 70 80 3.96 0.7865
WVFGRD96 18.0 145 70 80 3.97 0.8222
WVFGRD96 20.0 350 25 110 3.99 0.8439
WVFGRD96 22.0 145 70 80 4.01 0.8545
WVFGRD96 24.0 145 70 80 4.02 0.8557
WVFGRD96 26.0 345 20 110 4.03 0.8480
WVFGRD96 28.0 145 70 85 4.04 0.8327
WVFGRD96 30.0 345 20 110 4.05 0.8103
WVFGRD96 32.0 150 70 90 4.05 0.7807
WVFGRD96 34.0 150 70 90 4.06 0.7472
WVFGRD96 36.0 150 70 90 4.07 0.7133
WVFGRD96 38.0 150 70 90 4.07 0.6812
WVFGRD96 40.0 155 75 90 4.20 0.6512
WVFGRD96 42.0 155 75 90 4.20 0.6208
WVFGRD96 44.0 330 15 85 4.21 0.5920
WVFGRD96 46.0 330 15 85 4.22 0.5658
WVFGRD96 48.0 325 20 80 4.23 0.5413
WVFGRD96 50.0 320 20 70 4.23 0.5198
WVFGRD96 52.0 315 20 65 4.24 0.4988
WVFGRD96 54.0 310 20 60 4.25 0.4792
WVFGRD96 56.0 300 15 50 4.24 0.4609
WVFGRD96 58.0 150 80 75 4.25 0.4463
WVFGRD96 60.0 145 85 75 4.26 0.4330
WVFGRD96 62.0 325 90 -80 4.25 0.4214
WVFGRD96 64.0 325 90 -80 4.26 0.4130
WVFGRD96 66.0 145 90 80 4.27 0.4045
WVFGRD96 68.0 145 90 80 4.27 0.3957
WVFGRD96 70.0 145 90 80 4.28 0.3868
WVFGRD96 72.0 320 85 -80 4.28 0.3820
WVFGRD96 74.0 315 80 -80 4.28 0.3808
WVFGRD96 76.0 320 80 -85 4.29 0.3808
WVFGRD96 78.0 160 15 -70 4.29 0.3811
WVFGRD96 80.0 320 75 -95 4.30 0.3819
WVFGRD96 82.0 165 15 -65 4.31 0.3828
WVFGRD96 84.0 155 15 -75 4.31 0.3821
WVFGRD96 86.0 325 60 -70 4.29 0.3847
WVFGRD96 88.0 320 55 -80 4.30 0.3907
WVFGRD96 90.0 320 55 -80 4.31 0.3979
WVFGRD96 92.0 320 55 -80 4.31 0.4049
WVFGRD96 94.0 320 55 -80 4.32 0.4112
WVFGRD96 96.0 320 55 -80 4.32 0.4165
WVFGRD96 98.0 325 55 -85 4.33 0.4216
WVFGRD96 100.0 135 35 -100 4.33 0.4260
WVFGRD96 102.0 325 55 -85 4.33 0.4297
WVFGRD96 104.0 135 35 -100 4.34 0.4331
WVFGRD96 106.0 135 35 -100 4.34 0.4361
WVFGRD96 108.0 140 35 -95 4.34 0.4383
The best solution is
WVFGRD96 24.0 145 70 80 4.02 0.8557
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: