2014/04/07 14:03:42 -20.145 -70.942 7.3 5.1 Chile
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2014/04/07 14:03:42:0 -20.15 -70.94 7.3 5.1 Chile
Stations used:
CX.MNMCX CX.PATCX CX.PB04 CX.PB07 CX.PB08 CX.PB09 CX.PB11
CX.PB12 CX.PB16 CX.PSGCX
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 = 1.27e+23 dyne-cm
Mw = 4.67
Z = 16 km
Plane Strike Dip Rake
NP1 280 80 65
NP2 170 27 157
Principal Axes:
Axis Value Plunge Azimuth
T 1.27e+23 49 163
N 0.00e+00 25 285
P -1.27e+23 31 30
Moment Tensor: (dyne-cm)
Component Value
Mxx -2.02e+22
Mxy -5.66e+22
Mxz -1.08e+23
Myy -1.93e+22
Myz -9.63e+21
Mzz 3.95e+22
#-------------
###-------------------
####------------------------
###------------------ ------
####------------------- P --------
####-------------------- ---------
#####---------------------------------
#####-----------------------------------
#####-----------------------------------
------##############----------------------
-----########################-------------
------#############################-------
------##################################--
-----###################################
------##################################
------############### ##############
------############## T #############
------############# ############
-----#########################
------######################
------################
------########
Global CMT Convention Moment Tensor:
R T P
3.95e+22 -1.08e+23 9.63e+21
-1.08e+23 -2.02e+22 5.66e+22
9.63e+21 5.66e+22 -1.93e+22
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20140407140342/index.html
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STK = 280
DIP = 80
RAKE = 65
MW = 4.67
HS = 16.0
The NDK file is 20140407140342.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2014/04/07 14:03:42:0 -20.15 -70.94 7.3 5.1 Chile
Stations used:
CX.MNMCX CX.PATCX CX.PB04 CX.PB07 CX.PB08 CX.PB09 CX.PB11
CX.PB12 CX.PB16 CX.PSGCX
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 = 1.27e+23 dyne-cm
Mw = 4.67
Z = 16 km
Plane Strike Dip Rake
NP1 280 80 65
NP2 170 27 157
Principal Axes:
Axis Value Plunge Azimuth
T 1.27e+23 49 163
N 0.00e+00 25 285
P -1.27e+23 31 30
Moment Tensor: (dyne-cm)
Component Value
Mxx -2.02e+22
Mxy -5.66e+22
Mxz -1.08e+23
Myy -1.93e+22
Myz -9.63e+21
Mzz 3.95e+22
#-------------
###-------------------
####------------------------
###------------------ ------
####------------------- P --------
####-------------------- ---------
#####---------------------------------
#####-----------------------------------
#####-----------------------------------
------##############----------------------
-----########################-------------
------#############################-------
------##################################--
-----###################################
------##################################
------############### ##############
------############## T #############
------############# ############
-----#########################
------######################
------################
------########
Global CMT Convention Moment Tensor:
R T P
3.95e+22 -1.08e+23 9.63e+21
-1.08e+23 -2.02e+22 5.66e+22
9.63e+21 5.66e+22 -1.93e+22
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20140407140342/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 2.0 125 45 95 4.43 0.3356
WVFGRD96 4.0 280 60 30 4.47 0.2698
WVFGRD96 6.0 95 90 -65 4.55 0.3351
WVFGRD96 8.0 280 85 75 4.63 0.3918
WVFGRD96 10.0 285 80 75 4.63 0.4394
WVFGRD96 12.0 280 80 70 4.65 0.4646
WVFGRD96 14.0 280 80 70 4.66 0.4752
WVFGRD96 16.0 280 80 65 4.67 0.4757
WVFGRD96 18.0 280 85 65 4.68 0.4701
WVFGRD96 20.0 280 85 65 4.69 0.4596
WVFGRD96 22.0 280 85 70 4.71 0.4459
WVFGRD96 24.0 280 85 70 4.72 0.4301
WVFGRD96 26.0 280 85 70 4.73 0.4117
WVFGRD96 28.0 275 85 70 4.75 0.3923
WVFGRD96 30.0 275 85 70 4.76 0.3716
WVFGRD96 32.0 275 85 70 4.76 0.3499
WVFGRD96 34.0 275 85 70 4.77 0.3277
WVFGRD96 36.0 275 85 65 4.77 0.3061
WVFGRD96 38.0 275 80 70 4.76 0.2861
WVFGRD96 40.0 90 90 -80 4.91 0.2695
WVFGRD96 42.0 175 35 -10 4.93 0.2675
WVFGRD96 44.0 170 35 -15 4.94 0.2628
WVFGRD96 46.0 170 40 -15 4.95 0.2572
WVFGRD96 48.0 170 40 -10 4.97 0.2510
WVFGRD96 50.0 170 40 -10 4.98 0.2429
WVFGRD96 52.0 170 45 -10 4.98 0.2356
WVFGRD96 54.0 170 45 -15 4.98 0.2264
WVFGRD96 56.0 175 50 -5 5.00 0.2186
WVFGRD96 58.0 175 50 -5 5.00 0.2114
WVFGRD96 60.0 0 80 -30 4.97 0.2063
WVFGRD96 62.0 0 80 -30 4.97 0.2041
WVFGRD96 64.0 0 80 -30 4.97 0.1996
WVFGRD96 66.0 0 75 -30 4.98 0.1971
WVFGRD96 68.0 0 75 -30 4.98 0.1979
WVFGRD96 70.0 0 75 -30 4.98 0.1985
WVFGRD96 72.0 0 75 -30 4.98 0.1972
WVFGRD96 74.0 0 70 -30 4.98 0.1976
WVFGRD96 76.0 0 70 -30 4.99 0.1983
WVFGRD96 78.0 0 70 -30 4.99 0.1977
WVFGRD96 80.0 0 70 -30 4.99 0.1989
WVFGRD96 82.0 0 70 -30 4.99 0.1983
WVFGRD96 84.0 0 70 -30 4.99 0.1993
WVFGRD96 86.0 0 70 -30 4.99 0.2002
WVFGRD96 88.0 0 70 -30 4.99 0.1996
WVFGRD96 90.0 0 70 -30 4.99 0.1998
WVFGRD96 92.0 0 65 -30 4.99 0.1988
WVFGRD96 94.0 0 65 -30 4.99 0.1990
WVFGRD96 96.0 0 65 -30 4.99 0.1988
WVFGRD96 98.0 0 65 -30 4.99 0.1989
WVFGRD96 100.0 0 65 -30 4.99 0.1983
WVFGRD96 102.0 0 65 -30 5.00 0.1984
WVFGRD96 104.0 0 65 -30 5.00 0.1984
WVFGRD96 106.0 0 65 -30 5.00 0.1987
WVFGRD96 108.0 0 65 -30 5.00 0.1988
The best solution is
WVFGRD96 16.0 280 80 65 4.67 0.4757
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: