2014/04/05 14:04:49 -20.353 -70.864 10.0 4.8 Chile
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2014/04/05 14:04:49:0 -20.35 -70.86 10.0 4.8 Chile
Stations used:
CX.MNMCX CX.PATCX CX.PB01 CX.PB04 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 = 2.07e+23 dyne-cm
Mw = 4.81
Z = 12 km
Plane Strike Dip Rake
NP1 326 60 93
NP2 140 30 85
Principal Axes:
Axis Value Plunge Azimuth
T 2.07e+23 75 244
N 0.00e+00 2 144
P -2.07e+23 15 54
Moment Tensor: (dyne-cm)
Component Value
Mxx -6.48e+22
Mxy -8.62e+22
Mxz -5.42e+22
Myy -1.13e+23
Myz -8.88e+22
Mzz 1.78e+23
--------------
----------------------
-######---------------------
############------------------
--##############-------------- -
--#################------------ P --
---###################---------- ---
---######################---------------
---#######################--------------
-----#######################--------------
-----########################-------------
-----######### #############------------
------######## T ##############-----------
------####### ###############---------
-------########################---------
-------########################-------
-------#######################------
--------#####################-----
---------##################---
-----------###############--
----------------------
--------------
Global CMT Convention Moment Tensor:
R T P
1.78e+23 -5.42e+22 8.88e+22
-5.42e+22 -6.48e+22 8.62e+22
8.88e+22 8.62e+22 -1.13e+23
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20140405140449/index.html
|
STK = 140
DIP = 30
RAKE = 85
MW = 4.81
HS = 12.0
The NDK file is 20140405140449.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2014/04/05 14:04:49:0 -20.35 -70.86 10.0 4.8 Chile
Stations used:
CX.MNMCX CX.PATCX CX.PB01 CX.PB04 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 = 2.07e+23 dyne-cm
Mw = 4.81
Z = 12 km
Plane Strike Dip Rake
NP1 326 60 93
NP2 140 30 85
Principal Axes:
Axis Value Plunge Azimuth
T 2.07e+23 75 244
N 0.00e+00 2 144
P -2.07e+23 15 54
Moment Tensor: (dyne-cm)
Component Value
Mxx -6.48e+22
Mxy -8.62e+22
Mxz -5.42e+22
Myy -1.13e+23
Myz -8.88e+22
Mzz 1.78e+23
--------------
----------------------
-######---------------------
############------------------
--##############-------------- -
--#################------------ P --
---###################---------- ---
---######################---------------
---#######################--------------
-----#######################--------------
-----########################-------------
-----######### #############------------
------######## T ##############-----------
------####### ###############---------
-------########################---------
-------########################-------
-------#######################------
--------#####################-----
---------##################---
-----------###############--
----------------------
--------------
Global CMT Convention Moment Tensor:
R T P
1.78e+23 -5.42e+22 8.88e+22
-5.42e+22 -6.48e+22 8.62e+22
8.88e+22 8.62e+22 -1.13e+23
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20140405140449/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 2.0 280 70 30 4.53 0.3742
WVFGRD96 4.0 280 85 60 4.65 0.3600
WVFGRD96 6.0 120 15 55 4.68 0.4833
WVFGRD96 8.0 130 20 70 4.78 0.5734
WVFGRD96 10.0 140 25 85 4.80 0.6536
WVFGRD96 12.0 140 30 85 4.81 0.6936
WVFGRD96 14.0 140 35 85 4.82 0.6878
WVFGRD96 16.0 145 35 90 4.81 0.6526
WVFGRD96 18.0 320 55 85 4.81 0.6042
WVFGRD96 20.0 315 60 80 4.80 0.5517
WVFGRD96 22.0 165 45 -60 4.81 0.5217
WVFGRD96 24.0 165 45 -60 4.81 0.4923
WVFGRD96 26.0 170 45 -55 4.82 0.4619
WVFGRD96 28.0 175 45 -50 4.82 0.4309
WVFGRD96 30.0 175 45 -50 4.83 0.4001
WVFGRD96 32.0 175 45 -50 4.83 0.3687
WVFGRD96 34.0 170 40 -60 4.83 0.3380
WVFGRD96 36.0 175 40 -55 4.83 0.3093
WVFGRD96 38.0 175 40 -55 4.85 0.2825
WVFGRD96 40.0 165 35 -65 4.97 0.2752
WVFGRD96 42.0 170 40 -55 4.97 0.2519
WVFGRD96 44.0 170 40 -55 4.98 0.2355
WVFGRD96 46.0 180 50 -25 5.00 0.2213
WVFGRD96 48.0 180 50 -25 5.01 0.2101
WVFGRD96 50.0 180 55 -25 5.02 0.2002
WVFGRD96 52.0 185 55 -20 5.02 0.1919
WVFGRD96 54.0 185 55 -15 5.03 0.1859
WVFGRD96 56.0 185 55 -15 5.04 0.1817
WVFGRD96 58.0 185 60 -10 5.05 0.1798
WVFGRD96 60.0 185 65 -10 5.05 0.1812
WVFGRD96 62.0 185 65 -10 5.06 0.1831
WVFGRD96 64.0 185 65 -10 5.07 0.1840
WVFGRD96 66.0 185 65 -10 5.07 0.1831
WVFGRD96 68.0 185 70 -5 5.08 0.1834
WVFGRD96 70.0 185 70 -5 5.08 0.1840
WVFGRD96 72.0 185 70 -5 5.09 0.1846
WVFGRD96 74.0 185 70 -5 5.09 0.1857
WVFGRD96 76.0 185 70 -5 5.10 0.1848
WVFGRD96 78.0 185 70 -5 5.10 0.1861
WVFGRD96 80.0 185 75 -5 5.10 0.1885
WVFGRD96 82.0 185 75 -5 5.11 0.1905
WVFGRD96 84.0 185 75 -5 5.11 0.1909
WVFGRD96 86.0 185 75 -5 5.12 0.1931
WVFGRD96 88.0 185 75 -5 5.12 0.1939
WVFGRD96 90.0 185 80 -5 5.12 0.1947
WVFGRD96 92.0 185 80 -5 5.12 0.1958
WVFGRD96 94.0 185 80 -5 5.12 0.1965
WVFGRD96 96.0 185 80 -5 5.13 0.1969
WVFGRD96 98.0 185 80 -5 5.13 0.1972
WVFGRD96 100.0 185 80 -5 5.13 0.1975
WVFGRD96 102.0 185 85 -5 5.13 0.1973
WVFGRD96 104.0 185 85 -5 5.13 0.1977
WVFGRD96 106.0 185 90 -5 5.13 0.1999
WVFGRD96 108.0 185 90 -5 5.13 0.1993
The best solution is
WVFGRD96 12.0 140 30 85 4.81 0.6936
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: