2014/04/09 11:14:45 -20.593 -70.747 15.7 5.4 Chile
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2014/04/09 11:14:45:0 -20.59 -70.75 15.7 5.4 Chile
Stations used:
CX.MNMCX CX.PATCX CX.PB01 CX.PB02 CX.PB03 CX.PB04 CX.PB05
CX.PB06 CX.PB07 CX.PB08 CX.PB09 CX.PB10 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 = 6.03e+23 dyne-cm
Mw = 5.12
Z = 16 km
Plane Strike Dip Rake
NP1 170 65 85
NP2 2 25 101
Principal Axes:
Axis Value Plunge Azimuth
T 6.03e+23 70 70
N 0.00e+00 5 172
P -6.03e+23 20 264
Moment Tensor: (dyne-cm)
Component Value
Mxx 2.41e+21
Mxy -3.39e+22
Mxz 8.89e+22
Myy -4.62e+23
Myz 3.76e+23
Mzz 4.60e+23
---########---
------############----
--------###############-----
---------#################----
----------###################-----
-----------####################-----
------------#####################-----
-------------######################-----
-------------######################-----
--------------######## ############-----
--------------######## T ############-----
--- ---------####### ############-----
--- P ---------#####################------
-- ----------####################-----
---------------####################-----
---------------##################-----
--------------#################-----
--------------###############-----
-------------#############----
-------------##########-----
------------######----
---------#----
Global CMT Convention Moment Tensor:
R T P
4.60e+23 8.89e+22 -3.76e+23
8.89e+22 2.41e+21 3.39e+22
-3.76e+23 3.39e+22 -4.62e+23
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20140409111445/index.html
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STK = 170
DIP = 65
RAKE = 85
MW = 5.12
HS = 16.0
The NDK file is 20140409111445.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2014/04/09 11:14:45:0 -20.59 -70.75 15.7 5.4 Chile
Stations used:
CX.MNMCX CX.PATCX CX.PB01 CX.PB02 CX.PB03 CX.PB04 CX.PB05
CX.PB06 CX.PB07 CX.PB08 CX.PB09 CX.PB10 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 = 6.03e+23 dyne-cm
Mw = 5.12
Z = 16 km
Plane Strike Dip Rake
NP1 170 65 85
NP2 2 25 101
Principal Axes:
Axis Value Plunge Azimuth
T 6.03e+23 70 70
N 0.00e+00 5 172
P -6.03e+23 20 264
Moment Tensor: (dyne-cm)
Component Value
Mxx 2.41e+21
Mxy -3.39e+22
Mxz 8.89e+22
Myy -4.62e+23
Myz 3.76e+23
Mzz 4.60e+23
---########---
------############----
--------###############-----
---------#################----
----------###################-----
-----------####################-----
------------#####################-----
-------------######################-----
-------------######################-----
--------------######## ############-----
--------------######## T ############-----
--- ---------####### ############-----
--- P ---------#####################------
-- ----------####################-----
---------------####################-----
---------------##################-----
--------------#################-----
--------------###############-----
-------------#############----
-------------##########-----
------------######----
---------#----
Global CMT Convention Moment Tensor:
R T P
4.60e+23 8.89e+22 -3.76e+23
8.89e+22 2.41e+21 3.39e+22
-3.76e+23 3.39e+22 -4.62e+23
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20140409111445/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 10 40 -90 4.85 0.3774
WVFGRD96 4.0 280 15 5 4.97 0.3326
WVFGRD96 6.0 300 10 35 4.98 0.4733
WVFGRD96 8.0 175 80 90 5.06 0.5658
WVFGRD96 10.0 170 75 85 5.08 0.6554
WVFGRD96 12.0 170 70 85 5.10 0.7209
WVFGRD96 14.0 170 65 85 5.11 0.7591
WVFGRD96 16.0 170 65 85 5.12 0.7727
WVFGRD96 18.0 170 65 80 5.13 0.7675
WVFGRD96 20.0 170 65 80 5.13 0.7506
WVFGRD96 22.0 170 65 85 5.15 0.7283
WVFGRD96 24.0 170 65 85 5.15 0.6985
WVFGRD96 26.0 165 70 75 5.16 0.6665
WVFGRD96 28.0 165 70 75 5.17 0.6327
WVFGRD96 30.0 165 70 75 5.18 0.5970
WVFGRD96 32.0 165 70 75 5.18 0.5591
WVFGRD96 34.0 165 70 75 5.19 0.5202
WVFGRD96 36.0 370 20 110 5.19 0.4833
WVFGRD96 38.0 340 15 80 5.18 0.4503
WVFGRD96 40.0 170 75 90 5.33 0.4298
WVFGRD96 42.0 170 75 90 5.33 0.3945
WVFGRD96 44.0 325 20 60 5.32 0.3608
WVFGRD96 46.0 320 20 55 5.33 0.3312
WVFGRD96 48.0 335 50 55 5.34 0.3097
WVFGRD96 50.0 330 55 45 5.34 0.2919
WVFGRD96 52.0 330 50 45 5.34 0.2765
WVFGRD96 54.0 330 50 45 5.34 0.2633
WVFGRD96 56.0 160 70 45 5.35 0.2509
WVFGRD96 58.0 325 50 40 5.35 0.2415
WVFGRD96 60.0 150 35 50 5.32 0.2396
WVFGRD96 62.0 145 40 45 5.32 0.2360
WVFGRD96 64.0 150 40 45 5.33 0.2390
WVFGRD96 66.0 150 40 45 5.34 0.2378
WVFGRD96 68.0 155 40 50 5.35 0.2431
WVFGRD96 70.0 155 45 50 5.35 0.2435
WVFGRD96 72.0 155 45 50 5.36 0.2428
WVFGRD96 74.0 160 45 55 5.37 0.2491
WVFGRD96 76.0 160 45 55 5.37 0.2511
WVFGRD96 78.0 160 45 55 5.37 0.2505
WVFGRD96 80.0 160 50 55 5.38 0.2570
WVFGRD96 82.0 165 45 70 5.39 0.2579
WVFGRD96 84.0 165 45 70 5.39 0.2600
WVFGRD96 86.0 165 45 70 5.40 0.2621
WVFGRD96 88.0 170 45 75 5.40 0.2667
WVFGRD96 90.0 170 45 75 5.41 0.2681
WVFGRD96 92.0 170 45 75 5.41 0.2693
WVFGRD96 94.0 170 50 75 5.41 0.2719
WVFGRD96 96.0 170 50 75 5.42 0.2733
WVFGRD96 98.0 170 50 75 5.42 0.2764
WVFGRD96 100.0 170 50 75 5.42 0.2770
WVFGRD96 102.0 170 50 75 5.42 0.2782
WVFGRD96 104.0 170 50 75 5.42 0.2784
WVFGRD96 106.0 170 55 75 5.43 0.2795
WVFGRD96 108.0 180 50 -90 5.43 0.2783
The best solution is
WVFGRD96 16.0 170 65 85 5.12 0.7727
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: