2014/04/10 10:25:32 -26.832 -71.120 26.4 4.6 Chile
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2014/04/10 10:25:32:0 -26.83 -71.12 26.4 4.6 Chile
Stations used:
C.GO02 C.GO03 C.GO04 CX.PB04 CX.PB06 CX.PB07 CX.PB09
CX.PB10 CX.PB14 CX.PB15 IU.LCO 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 = 5.56e+22 dyne-cm
Mw = 4.43
Z = 28 km
Plane Strike Dip Rake
NP1 170 65 85
NP2 2 25 101
Principal Axes:
Axis Value Plunge Azimuth
T 5.56e+22 70 70
N 0.00e+00 5 172
P -5.56e+22 20 264
Moment Tensor: (dyne-cm)
Component Value
Mxx 2.23e+20
Mxy -3.13e+21
Mxz 8.20e+21
Myy -4.26e+22
Myz 3.47e+22
Mzz 4.24e+22
---########---
------############----
--------###############-----
---------#################----
----------###################-----
-----------####################-----
------------#####################-----
-------------######################-----
-------------######################-----
--------------######## ############-----
--------------######## T ############-----
--- ---------####### ############-----
--- P ---------#####################------
-- ----------####################-----
---------------####################-----
---------------##################-----
--------------#################-----
--------------###############-----
-------------#############----
-------------##########-----
------------######----
---------#----
Global CMT Convention Moment Tensor:
R T P
4.24e+22 8.20e+21 -3.47e+22
8.20e+21 2.23e+20 3.13e+21
-3.47e+22 3.13e+21 -4.26e+22
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20140410102532/index.html
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STK = 170
DIP = 65
RAKE = 85
MW = 4.43
HS = 28.0
The NDK file is 20140410102532.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2014/04/10 10:25:32:0 -26.83 -71.12 26.4 4.6 Chile
Stations used:
C.GO02 C.GO03 C.GO04 CX.PB04 CX.PB06 CX.PB07 CX.PB09
CX.PB10 CX.PB14 CX.PB15 IU.LCO 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 = 5.56e+22 dyne-cm
Mw = 4.43
Z = 28 km
Plane Strike Dip Rake
NP1 170 65 85
NP2 2 25 101
Principal Axes:
Axis Value Plunge Azimuth
T 5.56e+22 70 70
N 0.00e+00 5 172
P -5.56e+22 20 264
Moment Tensor: (dyne-cm)
Component Value
Mxx 2.23e+20
Mxy -3.13e+21
Mxz 8.20e+21
Myy -4.26e+22
Myz 3.47e+22
Mzz 4.24e+22
---########---
------############----
--------###############-----
---------#################----
----------###################-----
-----------####################-----
------------#####################-----
-------------######################-----
-------------######################-----
--------------######## ############-----
--------------######## T ############-----
--- ---------####### ############-----
--- P ---------#####################------
-- ----------####################-----
---------------####################-----
---------------##################-----
--------------#################-----
--------------###############-----
-------------#############----
-------------##########-----
------------######----
---------#----
Global CMT Convention Moment Tensor:
R T P
4.24e+22 8.20e+21 -3.47e+22
8.20e+21 2.23e+20 3.13e+21
-3.47e+22 3.13e+21 -4.26e+22
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20140410102532/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 45 -90 4.11 0.3616
WVFGRD96 4.0 255 90 5 4.05 0.3069
WVFGRD96 6.0 180 10 -85 4.17 0.3254
WVFGRD96 8.0 180 10 -80 4.27 0.4123
WVFGRD96 10.0 170 15 -90 4.29 0.5103
WVFGRD96 12.0 170 15 -90 4.31 0.5815
WVFGRD96 14.0 175 15 -85 4.32 0.6287
WVFGRD96 16.0 170 15 -90 4.34 0.6600
WVFGRD96 18.0 165 15 -95 4.35 0.6792
WVFGRD96 20.0 165 15 -95 4.36 0.6896
WVFGRD96 22.0 170 65 85 4.39 0.7093
WVFGRD96 24.0 170 65 85 4.40 0.7285
WVFGRD96 26.0 170 65 85 4.42 0.7391
WVFGRD96 28.0 170 65 85 4.43 0.7412
WVFGRD96 30.0 170 65 85 4.44 0.7351
WVFGRD96 32.0 170 65 85 4.45 0.7201
WVFGRD96 34.0 170 65 85 4.46 0.6983
WVFGRD96 36.0 165 70 80 4.48 0.6719
WVFGRD96 38.0 165 70 80 4.48 0.6432
WVFGRD96 40.0 365 20 105 4.61 0.6125
WVFGRD96 42.0 365 20 110 4.63 0.5858
WVFGRD96 44.0 365 20 110 4.63 0.5586
WVFGRD96 46.0 365 20 110 4.64 0.5328
WVFGRD96 48.0 365 20 110 4.65 0.5089
WVFGRD96 50.0 165 75 80 4.65 0.4886
WVFGRD96 52.0 165 75 80 4.66 0.4701
WVFGRD96 54.0 165 75 85 4.67 0.4546
WVFGRD96 56.0 280 80 -65 4.61 0.4414
WVFGRD96 58.0 280 80 -65 4.62 0.4293
WVFGRD96 60.0 280 85 -60 4.62 0.4164
WVFGRD96 62.0 110 20 -60 4.61 0.4040
WVFGRD96 64.0 125 25 -40 4.62 0.3954
WVFGRD96 66.0 125 25 -35 4.62 0.3875
WVFGRD96 68.0 130 25 -30 4.62 0.3799
WVFGRD96 70.0 130 25 -30 4.63 0.3727
WVFGRD96 72.0 135 25 -20 4.63 0.3666
WVFGRD96 74.0 135 25 -20 4.63 0.3610
WVFGRD96 76.0 140 30 -10 4.63 0.3566
WVFGRD96 78.0 135 40 35 4.65 0.3572
WVFGRD96 80.0 135 40 30 4.65 0.3569
WVFGRD96 82.0 140 40 35 4.65 0.3570
WVFGRD96 84.0 140 40 35 4.66 0.3565
WVFGRD96 86.0 145 35 35 4.66 0.3563
WVFGRD96 88.0 145 35 35 4.66 0.3553
WVFGRD96 90.0 150 35 40 4.66 0.3542
WVFGRD96 92.0 150 35 40 4.67 0.3540
WVFGRD96 94.0 150 35 40 4.67 0.3532
WVFGRD96 96.0 155 35 40 4.67 0.3515
WVFGRD96 98.0 150 35 40 4.68 0.3501
WVFGRD96 100.0 155 35 40 4.67 0.3483
WVFGRD96 102.0 155 35 45 4.68 0.3459
WVFGRD96 104.0 155 35 45 4.68 0.3433
WVFGRD96 106.0 160 35 45 4.68 0.3406
WVFGRD96 108.0 160 35 45 4.68 0.3374
The best solution is
WVFGRD96 28.0 170 65 85 4.43 0.7412
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: