2014/04/15 16:09:34 -20.227 -70.831 18.7 5.2 Chile
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2014/04/15 16:09:34:0 -20.23 -70.83 18.7 5.2 Chile
Stations used:
C.GO01 C.GO02 CX.MNMCX CX.PATCX CX.PB01 CX.PB04 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 = 6.68e+23 dyne-cm
Mw = 5.15
Z = 20 km
Plane Strike Dip Rake
NP1 170 65 90
NP2 350 25 90
Principal Axes:
Axis Value Plunge Azimuth
T 6.68e+23 70 80
N 0.00e+00 -0 350
P -6.68e+23 20 260
Moment Tensor: (dyne-cm)
Component Value
Mxx -1.54e+22
Mxy -8.76e+22
Mxz 7.46e+22
Myy -4.97e+23
Myz 4.23e+23
Mzz 5.12e+23
---######-----
------###########-----
--------##############------
---------################-----
----------###################-----
-----------####################-----
------------#####################-----
-------------######################-----
-------------######################-----
--------------########### #########-----
--------------########### T #########-----
--- ---------########## #########-----
--- P ---------######################-----
-- ----------#####################----
---------------####################-----
---------------###################----
--------------##################----
--------------################----
-------------##############---
-------------###########----
------------#######---
---------####-
Global CMT Convention Moment Tensor:
R T P
5.12e+23 7.46e+22 -4.23e+23
7.46e+22 -1.54e+22 8.76e+22
-4.23e+23 8.76e+22 -4.97e+23
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20140415160934/index.html
|
STK = 350
DIP = 25
RAKE = 90
MW = 5.15
HS = 20.0
The NDK file is 20140415160934.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2014/04/15 16:09:34:0 -20.23 -70.83 18.7 5.2 Chile
Stations used:
C.GO01 C.GO02 CX.MNMCX CX.PATCX CX.PB01 CX.PB04 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 = 6.68e+23 dyne-cm
Mw = 5.15
Z = 20 km
Plane Strike Dip Rake
NP1 170 65 90
NP2 350 25 90
Principal Axes:
Axis Value Plunge Azimuth
T 6.68e+23 70 80
N 0.00e+00 -0 350
P -6.68e+23 20 260
Moment Tensor: (dyne-cm)
Component Value
Mxx -1.54e+22
Mxy -8.76e+22
Mxz 7.46e+22
Myy -4.97e+23
Myz 4.23e+23
Mzz 5.12e+23
---######-----
------###########-----
--------##############------
---------################-----
----------###################-----
-----------####################-----
------------#####################-----
-------------######################-----
-------------######################-----
--------------########### #########-----
--------------########### T #########-----
--- ---------########## #########-----
--- P ---------######################-----
-- ----------#####################----
---------------####################-----
---------------###################----
--------------##################----
--------------################----
-------------##############---
-------------###########----
------------#######---
---------####-
Global CMT Convention Moment Tensor:
R T P
5.12e+23 7.46e+22 -4.23e+23
7.46e+22 -1.54e+22 8.76e+22
-4.23e+23 8.76e+22 -4.97e+23
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20140415160934/index.html
|
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.
|
|
|
|
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 2.0 335 50 -90 4.89 0.4033
WVFGRD96 4.0 350 80 -80 4.99 0.3261
WVFGRD96 6.0 170 90 85 4.99 0.4677
WVFGRD96 8.0 170 90 85 5.07 0.5564
WVFGRD96 10.0 370 10 110 5.07 0.6405
WVFGRD96 12.0 355 15 95 5.09 0.7130
WVFGRD96 14.0 170 70 90 5.11 0.7718
WVFGRD96 16.0 345 25 85 5.13 0.8118
WVFGRD96 18.0 350 25 90 5.14 0.8319
WVFGRD96 20.0 350 25 90 5.15 0.8351
WVFGRD96 22.0 350 25 90 5.17 0.8266
WVFGRD96 24.0 350 25 90 5.18 0.8086
WVFGRD96 26.0 170 65 90 5.19 0.7831
WVFGRD96 28.0 170 65 90 5.19 0.7520
WVFGRD96 30.0 170 65 90 5.20 0.7157
WVFGRD96 32.0 355 25 95 5.20 0.6755
WVFGRD96 34.0 170 65 90 5.21 0.6324
WVFGRD96 36.0 170 65 90 5.22 0.5887
WVFGRD96 38.0 165 70 80 5.22 0.5478
WVFGRD96 40.0 360 15 100 5.35 0.5118
WVFGRD96 42.0 170 70 90 5.35 0.4719
WVFGRD96 44.0 170 70 85 5.35 0.4356
WVFGRD96 46.0 170 70 85 5.35 0.4018
WVFGRD96 48.0 170 70 85 5.35 0.3705
WVFGRD96 50.0 170 70 85 5.35 0.3415
WVFGRD96 52.0 170 75 -75 5.37 0.3236
WVFGRD96 54.0 170 75 -75 5.37 0.3096
WVFGRD96 56.0 170 75 -75 5.38 0.2957
WVFGRD96 58.0 170 80 -75 5.38 0.2817
WVFGRD96 60.0 170 80 -75 5.38 0.2684
WVFGRD96 62.0 170 80 -75 5.38 0.2577
WVFGRD96 64.0 170 85 -75 5.38 0.2489
WVFGRD96 66.0 335 75 60 5.38 0.2470
WVFGRD96 68.0 335 70 60 5.38 0.2481
WVFGRD96 70.0 335 70 60 5.39 0.2478
WVFGRD96 72.0 340 65 65 5.39 0.2515
WVFGRD96 74.0 335 65 60 5.39 0.2496
WVFGRD96 76.0 350 60 85 5.41 0.2640
WVFGRD96 78.0 350 60 85 5.41 0.2697
WVFGRD96 80.0 345 60 80 5.42 0.2829
WVFGRD96 82.0 350 55 85 5.42 0.2856
WVFGRD96 84.0 175 35 95 5.43 0.3012
WVFGRD96 86.0 175 35 95 5.44 0.3064
WVFGRD96 88.0 350 50 90 5.44 0.3117
WVFGRD96 90.0 170 40 90 5.45 0.3227
WVFGRD96 92.0 170 40 90 5.45 0.3316
WVFGRD96 94.0 170 40 90 5.46 0.3313
WVFGRD96 96.0 355 50 95 5.46 0.3396
WVFGRD96 98.0 170 45 90 5.46 0.3416
WVFGRD96 100.0 350 45 90 5.47 0.3472
WVFGRD96 102.0 350 45 90 5.47 0.3500
WVFGRD96 104.0 170 45 90 5.47 0.3500
WVFGRD96 106.0 170 45 90 5.47 0.3514
WVFGRD96 108.0 170 45 90 5.47 0.3522
The best solution is
WVFGRD96 20.0 350 25 90 5.15 0.8351
The mechanism correspond to the best fit is
|
|
|
The best fit as a function of depth is given in the following figure:
|
|
|
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
|
|
|
|
| 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: