Location
SLU location
First arrival times and P-wave first motions were picked, and the earthquake was located using the velocity model given below. The purpose was to check the conssitency between the waveform inversion focal mechanism and the observed P-wave first motions. The program elocate was used. The file elocate.txt give the observations and the result of running the location program.
KMA Location
2017/11/15 07:49:30 36.12 129.36 10.0 4.3 Korea
cat 20171115074930.msg >> index.html
cat >> index.html << EOF
Preferred Solution
The preferred solution from an analysis of the surface-wave spectral amplitude radiation pattern, waveform inversion and first motion observations is
STK = 350
DIP = 25
RAKE = 65
MW = 4.32
HS = 6.0
The NDK file is 20171115074930.ndk
The waveform inversion is preferred.
Moment Tensor Comparison
The following compares this source inversion to others
| SLU |
SLUFM |
USGS/SLU Moment Tensor Solution
ENS 2017/11/15 07:49:30:0 36.12 129.36 10.0 4.3 Korea
Stations used:
KS.BOSB KS.BUS2 KS.CHC2 KS.CHJ2 KS.DACB KS.DAG2 KS.DGY2
KS.EMSB KS.EURB KS.GAHB KS.GOCB KS.GWYB KS.HALB KS.HAMB
KS.HWCB KS.IMWB KS.JEO2 KS.KOHB KS.NAWB KS.OKCB KS.OKEB
KS.SEHB KS.SEO2 KS.SES2 KS.SHHB KS.SMKB KS.ULJ2 KS.YNCB
Filtering commands used:
cut o DIST/3.3 -20 o DIST/3.3 +40
rtr
taper w 0.1
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 3.80e+22 dyne-cm
Mw = 4.32
Z = 6 km
Plane Strike Dip Rake
NP1 197 67 101
NP2 350 25 65
Principal Axes:
Axis Value Plunge Azimuth
T 3.80e+22 66 127
N 0.00e+00 10 13
P -3.80e+22 22 279
Moment Tensor: (dyne-cm)
Component Value
Mxx 1.53e+21
Mxy 1.87e+21
Mxz -1.05e+22
Myy -2.79e+22
Myz 2.43e+22
Mzz 2.64e+22
---------####-
--------------###-----
----------------######------
---------------##########-----
----------------#############-----
----------------###############-----
----------------#################-----
----------------###################-----
-- -----------###################-----
--- P ----------#####################-----
--- ---------######################-----
---------------######################-----
--------------########### #########-----
-------------########### T #########----
-------------########### ########-----
------------######################----
----------######################----
---------#####################----
--------###################---
-------#################----
----###############---
-############-
Global CMT Convention Moment Tensor:
R T P
2.64e+22 -1.05e+22 -2.43e+22
-1.05e+22 1.53e+21 -1.87e+21
-2.43e+22 -1.87e+21 -2.79e+22
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20171115074930/index.html
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First motions and takeoff angles from an elocate run.
|
Magnitudes
mLg Magnitude
(a) mLg computed using the IASPEI formula; (b) mLg residuals ; the values used for the trimmed mean are indicated.
ML Magnitude
(a) ML computed using the IASPEI formula; (b) ML residuals computed using a modified IASPEI formula that accounts for path specific attenuation; the values used for the trimmed mean are indicated. The ML relation used for each figure is given at the bottom of each plot.
Waveform Inversion
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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Location of broadband stations used for waveform inversion
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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 o DIST/3.3 -20 o DIST/3.3 +40
rtr
taper w 0.1
hp c 0.02 n 3
lp c 0.10 n 3
The results of this grid search from 0.5 to 19 km depth are as follow:
DEPTH STK DIP RAKE MW FIT
WVFGRD96 1.0 190 25 80 4.28 0.6533
WVFGRD96 2.0 330 15 35 4.34 0.7067
WVFGRD96 3.0 330 20 40 4.32 0.7611
WVFGRD96 4.0 340 20 50 4.32 0.8042
WVFGRD96 5.0 345 25 60 4.32 0.8268
WVFGRD96 6.0 350 25 65 4.32 0.8399
WVFGRD96 7.0 350 25 65 4.32 0.8372
WVFGRD96 8.0 345 25 60 4.31 0.8255
WVFGRD96 9.0 335 30 50 4.31 0.8080
WVFGRD96 10.0 340 30 55 4.31 0.7870
WVFGRD96 11.0 335 30 50 4.31 0.7633
WVFGRD96 12.0 335 30 50 4.32 0.7397
WVFGRD96 13.0 330 30 40 4.32 0.7137
WVFGRD96 14.0 330 30 40 4.32 0.6871
WVFGRD96 15.0 330 30 40 4.32 0.6601
WVFGRD96 16.0 330 30 40 4.33 0.6322
WVFGRD96 17.0 330 30 40 4.34 0.6066
WVFGRD96 18.0 325 30 35 4.35 0.5798
WVFGRD96 19.0 325 30 35 4.35 0.5538
WVFGRD96 20.0 325 30 30 4.36 0.5285
WVFGRD96 21.0 325 30 30 4.37 0.5057
WVFGRD96 22.0 325 35 30 4.37 0.4831
WVFGRD96 23.0 325 35 30 4.38 0.4610
WVFGRD96 24.0 325 35 30 4.39 0.4394
WVFGRD96 25.0 325 35 30 4.39 0.4200
The best solution is
WVFGRD96 6.0 350 25 65 4.32 0.8399
The mechanism correspond to the best fit is
|
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Figure 1. Waveform inversion focal mechanism
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The best fit as a function of depth is given in the following figure:
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Figure 2. Depth sensitivity for waveform mechanism
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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 o DIST/3.3 -20 o DIST/3.3 +40
rtr
taper w 0.1
hp c 0.02 n 3
lp c 0.10 n 3
|
|
Figure 3. Waveform comparison for selected depth. Red: observed; Blue - predicted. The time shift with respect to the model prediction is indicated. The percent of fit is also indicated.
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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.
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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:
- The origin time and epicentral distance are incorrect
- The velocity model used for the inversion is incorrect
- The velocity model used to define the P-arrival time is not the
same as the velocity model used for the waveform inversion
(assuming that the initial trace alignment is based on the
P arrival time)
Assuming only a mislocation, the time shifts are fit to a functional form:
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.
Discussion
Acknowledgements
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.
Velocity Model
The t6.invSNU.CUVEL.model was used for the waveform synthetic seismograms and for the surface wave eigenfunctions and dispersion is as follows:
MODEL.01
Model after 30 iterations
ISOTROPIC
KGS
SPHERICAL 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
1.0000 5.3800 3.0009 2.5772 0.118E-02 0.167E-02 0.00 0.00 1.00 1.00
1.0000 5.8057 3.2383 2.6606 0.118E-02 0.167E-02 0.00 0.00 1.00 1.00
1.0000 6.1732 3.4433 2.7513 0.118E-02 0.167E-02 0.00 0.00 1.00 1.00
3.0000 6.2872 3.5067 2.7862 0.118E-02 0.167E-02 0.00 0.00 1.00 1.00
5.0000 6.3245 3.5281 2.7970 0.118E-02 0.167E-02 0.00 0.00 1.00 1.00
5.0000 6.4165 3.5788 2.8248 0.118E-02 0.167E-02 0.00 0.00 1.00 1.00
4.0000 6.5576 3.6576 2.8653 0.118E-02 0.167E-02 0.00 0.00 1.00 1.00
5.0000 6.6402 3.7038 2.8865 0.118E-02 0.167E-02 0.00 0.00 1.00 1.00
2.5000 6.6540 3.7115 2.8897 0.118E-02 0.167E-02 0.00 0.00 1.00 1.00
2.5000 7.0960 3.9579 3.0111 0.118E-02 0.167E-02 0.00 0.00 1.00 1.00
2.5000 7.9155 4.4148 3.2804 0.118E-02 0.167E-02 0.00 0.00 1.00 1.00
2.5000 7.8925 4.4019 3.2735 0.118E-02 0.167E-02 0.00 0.00 1.00 1.00
5.0000 7.8665 4.3876 3.2643 0.118E-02 0.167E-02 0.00 0.00 1.00 1.00
5.0000 7.5675 4.2211 3.1625 0.118E-02 0.167E-02 0.00 0.00 1.00 1.00
5.0000 7.7550 4.3252 3.2262 0.118E-02 0.167E-02 0.00 0.00 1.00 1.00
5.0000 7.7602 4.3280 3.2282 0.118E-02 0.167E-02 0.00 0.00 1.00 1.00
5.0000 7.7958 4.3487 3.2398 0.118E-02 0.167E-02 0.00 0.00 1.00 1.00
5.0000 7.7415 4.3195 3.2217 0.118E-02 0.167E-02 0.00 0.00 1.00 1.00
5.0000 7.6497 4.2688 3.1915 0.118E-02 0.167E-02 0.00 0.00 1.00 1.00
5.0000 7.6408 4.2653 3.1889 0.118E-02 0.167E-02 0.00 0.00 1.00 1.00
5.0000 7.6666 4.2716 3.1976 0.118E-02 0.167E-02 0.00 0.00 1.00 1.00
5.0000 7.6699 4.2830 3.1986 0.118E-02 0.167E-02 0.00 0.00 1.00 1.00
5.0000 7.6780 4.2885 3.2014 0.118E-02 0.167E-02 0.00 0.00 1.00 1.00
5.0000 7.6816 4.2896 3.2028 0.118E-02 0.167E-02 0.00 0.00 1.00 1.00
5.0000 7.6946 4.2996 3.2072 0.118E-02 0.167E-02 0.00 0.00 1.00 1.00
10.0000 7.7349 4.3197 3.2208 0.118E-02 0.167E-02 0.00 0.00 1.00 1.00
10.0000 7.7791 4.3484 3.2355 0.118E-02 0.167E-02 0.00 0.00 1.00 1.00
10.0000 7.8331 4.3722 3.2536 0.862E-02 0.131E-01 0.00 0.00 1.00 1.00
10.0000 7.8824 4.3863 3.2703 0.862E-02 0.131E-01 0.00 0.00 1.00 1.00
10.0000 7.9360 4.4024 3.2883 0.855E-02 0.131E-01 0.00 0.00 1.00 1.00
10.0000 7.9967 4.4237 3.3088 0.847E-02 0.131E-01 0.00 0.00 1.00 1.00
10.0000 8.0529 4.4423 3.3289 0.847E-02 0.131E-01 0.00 0.00 1.00 1.00
10.0000 8.1110 4.4603 3.3496 0.833E-02 0.130E-01 0.00 0.00 1.00 1.00
10.0000 8.1762 4.4832 3.3728 0.826E-02 0.129E-01 0.00 0.00 1.00 1.00
10.0000 8.2410 4.5054 3.3959 0.813E-02 0.128E-01 0.00 0.00 1.00 1.00
10.0000 8.3022 4.5257 3.4176 0.806E-02 0.126E-01 0.00 0.00 1.00 1.00
10.0000 8.3635 4.5514 3.4395 0.474E-02 0.746E-02 0.00 0.00 1.00 1.00
10.0000 8.4257 4.5839 3.4617 0.472E-02 0.741E-02 0.00 0.00 1.00 1.00
10.0000 8.4845 4.6145 3.4827 0.469E-02 0.741E-02 0.00 0.00 1.00 1.00
10.0000 8.5403 4.6434 3.5020 0.467E-02 0.735E-02 0.00 0.00 1.00 1.00
10.0000 8.5934 4.6708 3.5199 0.465E-02 0.735E-02 0.00 0.00 1.00 1.00
10.0000 8.6436 4.6959 3.5369 0.463E-02 0.730E-02 0.00 0.00 1.00 1.00
10.0000 8.6912 4.7194 3.5530 0.461E-02 0.730E-02 0.00 0.00 1.00 1.00
10.0000 8.7365 4.7413 3.5684 0.459E-02 0.725E-02 0.00 0.00 1.00 1.00
10.0000 8.7797 4.7622 3.5831 0.455E-02 0.725E-02 0.00 0.00 1.00 1.00
10.0000 8.8199 4.7819 3.5967 0.452E-02 0.719E-02 0.00 0.00 1.00 1.00
10.0000 8.8587 4.8001 3.6099 0.450E-02 0.714E-02 0.00 0.00 1.00 1.00
10.0000 8.8958 4.8177 3.6226 0.448E-02 0.714E-02 0.00 0.00 1.00 1.00
10.0000 8.9314 4.8346 3.6347 0.446E-02 0.709E-02 0.00 0.00 1.00 1.00
10.0000 8.9647 4.8500 3.6461 0.442E-02 0.704E-02 0.00 0.00 1.00 1.00
10.0000 8.9962 4.8651 3.6569 0.441E-02 0.704E-02 0.00 0.00 1.00 1.00
10.0000 9.0263 4.8783 3.6685 0.439E-02 0.699E-02 0.00 0.00 1.00 1.00
10.0000 9.0547 4.8915 3.6800 0.435E-02 0.694E-02 0.00 0.00 1.00 1.00
10.0000 9.0822 4.9041 3.6911 0.433E-02 0.690E-02 0.00 0.00 1.00 1.00
10.0000 9.1091 4.9164 3.7020 0.431E-02 0.690E-02 0.00 0.00 1.00 1.00
10.0000 9.1346 4.9280 3.7123 0.427E-02 0.685E-02 0.00 0.00 1.00 1.00
10.0000 9.4876 5.1513 3.8537 0.388E-02 0.613E-02 0.00 0.00 1.00 1.00
10.0000 9.5095 5.1663 3.8624 0.388E-02 0.613E-02 0.00 0.00 1.00 1.00
10.0000 9.5299 5.1806 3.8703 0.386E-02 0.610E-02 0.00 0.00 1.00 1.00
10.0000 9.5507 5.1944 3.8784 0.386E-02 0.610E-02 0.00 0.00 1.00 1.00
10.0000 9.5706 5.2080 3.8861 0.385E-02 0.606E-02 0.00 0.00 1.00 1.00
10.0000 9.5900 5.2214 3.8937 0.385E-02 0.606E-02 0.00 0.00 1.00 1.00
10.0000 9.6090 5.2347 3.9011 0.383E-02 0.606E-02 0.00 0.00 1.00 1.00
10.0000 9.6272 5.2480 3.9081 0.383E-02 0.602E-02 0.00 0.00 1.00 1.00
10.0000 9.6458 5.2604 3.9154 0.383E-02 0.602E-02 0.00 0.00 1.00 1.00
10.0000 9.6794 5.2816 3.9282 0.382E-02 0.599E-02 0.00 0.00 1.00 1.00
10.0000 9.7130 5.3029 3.9409 0.382E-02 0.599E-02 0.00 0.00 1.00 1.00
10.0000 9.7466 5.3242 3.9537 0.380E-02 0.599E-02 0.00 0.00 1.00 1.00
10.0000 9.7799 5.3454 3.9664 0.380E-02 0.595E-02 0.00 0.00 1.00 1.00
10.0000 9.8137 5.3669 3.9792 0.380E-02 0.595E-02 0.00 0.00 1.00 1.00
10.0000 9.8473 5.3883 3.9920 0.379E-02 0.592E-02 0.00 0.00 1.00 1.00
10.0000 9.8808 5.4094 4.0047 0.379E-02 0.592E-02 0.00 0.00 1.00 1.00
0.0000 9.9144 5.4306 4.0175 0.377E-02 0.592E-02 0.00 0.00 1.00 1.00
Quality Control
Here we tabulate the reasons for not using certain digital data sets
The following stations did not have a valid response files:
Last Changed Wed Feb 14 12:03:58 CST 2018