2014/03/24 12:48:04 -19.923 -70.903 14.9 4.4 Chile
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2014/03/24 12:48:04:0 -19.92 -70.90 14.9 4.4 Chile
Stations used:
C.GO01 C.GO02 CX.PATCX CX.PB01 CX.PB04 CX.PB07 CX.PB09
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 = 4.22e+22 dyne-cm
Mw = 4.35
Z = 20 km
Plane Strike Dip Rake
NP1 165 65 85
NP2 357 25 101
Principal Axes:
Axis Value Plunge Azimuth
T 4.22e+22 70 65
N 0.00e+00 5 167
P -4.22e+22 20 259
Moment Tensor: (dyne-cm)
Component Value
Mxx -4.90e+20
Mxy -5.16e+21
Mxz 8.49e+21
Myy -3.17e+22
Myz 2.57e+22
Mzz 3.22e+22
-#########----
-----############-----
-------################-----
--------##################----
---------####################-----
----------#####################-----
-----------######################-----
------------#######################-----
-------------########### ########-----
--------------########### T ########------
--------------########### #########-----
--- ---------######################-----
--- P ---------######################-----
-- ----------####################-----
---------------####################-----
---------------##################-----
---------------################-----
---------------##############-----
--------------############----
---------------#########----
-------------#####----
--------------
Global CMT Convention Moment Tensor:
R T P
3.22e+22 8.49e+21 -2.57e+22
8.49e+21 -4.90e+20 5.16e+21
-2.57e+22 5.16e+21 -3.17e+22
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20140324124804/index.html
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STK = 165
DIP = 65
RAKE = 85
MW = 4.35
HS = 20.0
The NDK file is 20140324124804.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2014/03/24 12:48:04:0 -19.92 -70.90 14.9 4.4 Chile
Stations used:
C.GO01 C.GO02 CX.PATCX CX.PB01 CX.PB04 CX.PB07 CX.PB09
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 = 4.22e+22 dyne-cm
Mw = 4.35
Z = 20 km
Plane Strike Dip Rake
NP1 165 65 85
NP2 357 25 101
Principal Axes:
Axis Value Plunge Azimuth
T 4.22e+22 70 65
N 0.00e+00 5 167
P -4.22e+22 20 259
Moment Tensor: (dyne-cm)
Component Value
Mxx -4.90e+20
Mxy -5.16e+21
Mxz 8.49e+21
Myy -3.17e+22
Myz 2.57e+22
Mzz 3.22e+22
-#########----
-----############-----
-------################-----
--------##################----
---------####################-----
----------#####################-----
-----------######################-----
------------#######################-----
-------------########### ########-----
--------------########### T ########------
--------------########### #########-----
--- ---------######################-----
--- P ---------######################-----
-- ----------####################-----
---------------####################-----
---------------##################-----
---------------################-----
---------------##############-----
--------------############----
---------------#########----
-------------#####----
--------------
Global CMT Convention Moment Tensor:
R T P
3.22e+22 8.49e+21 -2.57e+22
8.49e+21 -4.90e+20 5.16e+21
-2.57e+22 5.16e+21 -3.17e+22
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20140324124804/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 2.0 165 40 -90 4.10 0.4289 WVFGRD96 4.0 295 75 45 4.15 0.3057 WVFGRD96 6.0 230 10 -35 4.17 0.4276 WVFGRD96 8.0 240 10 -25 4.25 0.5126 WVFGRD96 10.0 255 10 -10 4.25 0.5956 WVFGRD96 12.0 170 75 85 4.28 0.6630 WVFGRD96 14.0 365 20 105 4.30 0.7244 WVFGRD96 16.0 360 25 100 4.32 0.7716 WVFGRD96 18.0 165 65 85 4.34 0.8000 WVFGRD96 20.0 165 65 85 4.35 0.8116 WVFGRD96 22.0 165 65 85 4.36 0.8113 WVFGRD96 24.0 165 65 85 4.37 0.8016 WVFGRD96 26.0 165 65 85 4.38 0.7849 WVFGRD96 28.0 165 65 85 4.39 0.7623 WVFGRD96 30.0 165 65 85 4.40 0.7345 WVFGRD96 32.0 160 65 80 4.41 0.7014 WVFGRD96 34.0 160 65 80 4.42 0.6640 WVFGRD96 36.0 160 65 80 4.42 0.6249 WVFGRD96 38.0 160 65 80 4.43 0.5856 WVFGRD96 40.0 350 20 95 4.55 0.5498 WVFGRD96 42.0 165 70 85 4.55 0.5130 WVFGRD96 44.0 160 65 85 4.57 0.4783 WVFGRD96 46.0 160 65 85 4.57 0.4462 WVFGRD96 48.0 160 65 80 4.57 0.4160 WVFGRD96 50.0 160 65 80 4.58 0.3890 WVFGRD96 52.0 160 65 80 4.58 0.3638 WVFGRD96 54.0 155 70 75 4.58 0.3414 WVFGRD96 56.0 155 70 75 4.58 0.3216 WVFGRD96 58.0 20 15 -55 4.58 0.3089 WVFGRD96 60.0 30 15 -45 4.58 0.3019 WVFGRD96 62.0 45 15 -30 4.58 0.2967 WVFGRD96 64.0 345 75 75 4.59 0.3021 WVFGRD96 66.0 345 70 75 4.60 0.3063 WVFGRD96 68.0 345 70 75 4.61 0.3118 WVFGRD96 70.0 345 70 75 4.61 0.3159 WVFGRD96 72.0 345 65 80 4.62 0.3216 WVFGRD96 74.0 345 65 80 4.63 0.3253 WVFGRD96 76.0 345 65 80 4.63 0.3256 WVFGRD96 78.0 350 60 85 4.64 0.3293 WVFGRD96 80.0 345 60 80 4.64 0.3337 WVFGRD96 82.0 345 60 80 4.64 0.3346 WVFGRD96 84.0 345 60 80 4.65 0.3358 WVFGRD96 86.0 345 60 80 4.65 0.3369 WVFGRD96 88.0 350 55 85 4.65 0.3366 WVFGRD96 90.0 350 55 85 4.65 0.3368 WVFGRD96 92.0 345 55 80 4.66 0.3375 WVFGRD96 94.0 345 55 80 4.66 0.3354 WVFGRD96 96.0 350 50 85 4.66 0.3340 WVFGRD96 98.0 350 50 85 4.66 0.3339 WVFGRD96 100.0 350 55 85 4.66 0.3385 WVFGRD96 102.0 135 30 70 4.67 0.3368 WVFGRD96 104.0 140 40 50 4.68 0.3400 WVFGRD96 106.0 175 45 -80 4.67 0.3472 WVFGRD96 108.0 175 45 -80 4.67 0.3505
The best solution is
WVFGRD96 20.0 165 65 85 4.35 0.8116
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: