2014/04/15 16:21:16 -20.160 -70.754 10.4 5.5 Chile
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2014/04/15 16:21:16:0 -20.16 -70.75 10.4 5.5 Chile
Stations used:
C.GO01 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 = 3.72e+23 dyne-cm
Mw = 4.98
Z = 10 km
Plane Strike Dip Rake
NP1 98 50 113
NP2 245 45 65
Principal Axes:
Axis Value Plunge Azimuth
T 3.72e+23 72 74
N 0.00e+00 17 263
P -3.72e+23 3 172
Moment Tensor: (dyne-cm)
Component Value
Mxx -3.62e+23
Mxy 5.76e+22
Mxz 4.69e+22
Myy 2.49e+22
Myz 1.01e+23
Mzz 3.37e+23
--------------
----------------------
----------------------------
------------------------------
-----------------############-----
-------------######################-
-----------###########################
---------###############################
-------#################################
#------################ ################
##---################## T ################
###-################### ################
###-######################################
##----#################################-
#-------#############################---
-----------#####################------
-------------------####-------------
----------------------------------
------------------------------
----------------------------
------------ -------
-------- P ---
Global CMT Convention Moment Tensor:
R T P
3.37e+23 4.69e+22 -1.01e+23
4.69e+22 -3.62e+23 -5.76e+22
-1.01e+23 -5.76e+22 2.49e+22
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20140415162116/index.html
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STK = 245
DIP = 45
RAKE = 65
MW = 4.98
HS = 10.0
The NDK file is 20140415162116.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2014/04/15 16:21:16:0 -20.16 -70.75 10.4 5.5 Chile
Stations used:
C.GO01 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 = 3.72e+23 dyne-cm
Mw = 4.98
Z = 10 km
Plane Strike Dip Rake
NP1 98 50 113
NP2 245 45 65
Principal Axes:
Axis Value Plunge Azimuth
T 3.72e+23 72 74
N 0.00e+00 17 263
P -3.72e+23 3 172
Moment Tensor: (dyne-cm)
Component Value
Mxx -3.62e+23
Mxy 5.76e+22
Mxz 4.69e+22
Myy 2.49e+22
Myz 1.01e+23
Mzz 3.37e+23
--------------
----------------------
----------------------------
------------------------------
-----------------############-----
-------------######################-
-----------###########################
---------###############################
-------#################################
#------################ ################
##---################## T ################
###-################### ################
###-######################################
##----#################################-
#-------#############################---
-----------#####################------
-------------------####-------------
----------------------------------
------------------------------
----------------------------
------------ -------
-------- P ---
Global CMT Convention Moment Tensor:
R T P
3.37e+23 4.69e+22 -1.01e+23
4.69e+22 -3.62e+23 -5.76e+22
-1.01e+23 -5.76e+22 2.49e+22
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20140415162116/index.html
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April 15, 2014, NEAR COAST OF NORTHERN CHILE, MW=5.1
Howard Koss
CENTROID-MOMENT-TENSOR SOLUTION
GCMT EVENT: C201404151621A
DATA: II DK IU MN G CU LD GE KP
IC
L.P.BODY WAVES: 71S, 83C, T= 40
SURFACE WAVES: 115S, 173C, T= 50
TIMESTAMP: Q-20140415144455
CENTROID LOCATION:
ORIGIN TIME: 16:21:22.0 0.2
LAT:20.21S 0.01;LON: 70.70W 0.02
DEP: 12.7 0.6;TRIANG HDUR: 0.9
MOMENT TENSOR: SCALE 10**23 D-CM
RR= 5.460 0.206; TT=-5.300 0.139
PP=-0.166 0.168; RT=-1.940 0.336
RP= 3.150 0.601; TP=-0.194 0.119
PRINCIPAL AXES:
1.(T) VAL= 7.146;PLG=65;AZM=250
2.(N) -1.486; 22; 99
3.(P) -5.666; 11; 4
BEST DBLE.COUPLE:M0= 6.41*10**23
NP1: STRIKE= 69;DIP=39;SLIP= 53
NP2: STRIKE=293;DIP=60;SLIP= 116
----- P ---
--------- -------
-----------------------
---------------------------
-----------------------------
################---------------
####################-----------
########################-------##
########## ##############----##
########## T ###############--###
########## ################-###
##########################----#
-#######################-------
--###################--------
-----##########------------
-----------------------
-------------------
-----------
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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 30 85 10 4.65 0.4040
WVFGRD96 4.0 220 40 15 4.80 0.4568
WVFGRD96 6.0 230 50 40 4.84 0.5486
WVFGRD96 8.0 240 45 60 4.95 0.6431
WVFGRD96 10.0 245 45 65 4.98 0.7032
WVFGRD96 12.0 245 45 65 4.98 0.6853
WVFGRD96 14.0 225 55 35 4.95 0.6467
WVFGRD96 16.0 225 60 30 4.95 0.6067
WVFGRD96 18.0 225 60 30 4.95 0.5700
WVFGRD96 20.0 220 65 20 4.96 0.5356
WVFGRD96 22.0 220 65 20 4.97 0.5050
WVFGRD96 24.0 220 65 20 4.98 0.4747
WVFGRD96 26.0 220 65 15 4.99 0.4478
WVFGRD96 28.0 220 65 15 5.00 0.4227
WVFGRD96 30.0 220 70 15 5.01 0.3999
WVFGRD96 32.0 220 70 15 5.02 0.3785
WVFGRD96 34.0 220 70 15 5.03 0.3588
WVFGRD96 36.0 220 75 15 5.04 0.3417
WVFGRD96 38.0 220 75 15 5.06 0.3289
WVFGRD96 40.0 215 80 20 5.12 0.3207
WVFGRD96 42.0 215 80 15 5.13 0.3135
WVFGRD96 44.0 215 80 15 5.14 0.3056
WVFGRD96 46.0 215 80 15 5.15 0.2977
WVFGRD96 48.0 215 80 15 5.16 0.2907
WVFGRD96 50.0 215 85 20 5.17 0.2842
WVFGRD96 52.0 215 80 15 5.18 0.2789
WVFGRD96 54.0 120 90 -20 5.20 0.2717
WVFGRD96 56.0 120 90 -20 5.21 0.2729
WVFGRD96 58.0 120 90 -20 5.22 0.2715
WVFGRD96 60.0 300 90 20 5.23 0.2731
WVFGRD96 62.0 120 90 -15 5.23 0.2741
WVFGRD96 64.0 120 90 -15 5.24 0.2728
WVFGRD96 66.0 120 80 -20 5.25 0.2689
WVFGRD96 68.0 120 80 -15 5.26 0.2702
WVFGRD96 70.0 120 80 -15 5.26 0.2708
WVFGRD96 72.0 120 80 -15 5.27 0.2724
WVFGRD96 74.0 210 80 5 5.27 0.2702
WVFGRD96 76.0 210 80 0 5.26 0.2718
WVFGRD96 78.0 35 70 -30 5.27 0.2769
WVFGRD96 80.0 35 65 -35 5.28 0.2792
WVFGRD96 82.0 35 60 -35 5.28 0.2829
WVFGRD96 84.0 35 60 -35 5.28 0.2865
WVFGRD96 86.0 20 40 -60 5.29 0.2886
WVFGRD96 88.0 25 40 -55 5.29 0.2929
WVFGRD96 90.0 25 40 -55 5.30 0.2962
WVFGRD96 92.0 20 35 -60 5.31 0.2997
WVFGRD96 94.0 20 35 -60 5.31 0.3028
WVFGRD96 96.0 20 35 -60 5.31 0.3060
WVFGRD96 98.0 25 35 -55 5.31 0.3087
WVFGRD96 100.0 25 35 -55 5.32 0.3120
WVFGRD96 102.0 20 30 -60 5.32 0.3144
WVFGRD96 104.0 20 30 -60 5.33 0.3174
WVFGRD96 106.0 20 30 -60 5.33 0.3197
WVFGRD96 108.0 20 30 -60 5.33 0.3226
The best solution is
WVFGRD96 10.0 245 45 65 4.98 0.7032
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: