2015/07/06 13:42:16 42.38 19.42 17 4.1 Montenegro
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2015/07/06 13:42:16:0 42.38 19.42 17.0 4.1 Montenegro
Stations used:
HT.THE HU.AMBH HU.BUD MN.BLY MN.DIVS MN.PDG MN.TIR MN.VTS
RO.BANR RO.BZS RO.DEV RO.LOT RO.PUNG SJ.BBLS SJ.FRGS
SL.CRES SL.KOGS
Filtering commands used:
cut o DIST/3.3 -30 o DIST/3.3 +70
rtr
taper w 0.1
hp c 0.02 n 3
lp c 0.06 n 3
Best Fitting Double Couple
Mo = 2.88e+22 dyne-cm
Mw = 4.24
Z = 25 km
Plane Strike Dip Rake
NP1 305 80 89
NP2 130 10 95
Principal Axes:
Axis Value Plunge Azimuth
T 2.88e+22 55 214
N 0.00e+00 1 305
P -2.88e+22 35 36
Moment Tensor: (dyne-cm)
Component Value
Mxx -6.20e+21
Mxy -4.76e+21
Mxz -2.23e+22
Myy -3.63e+21
Myz -1.55e+22
Mzz 9.83e+21
--------------
----------------------
----------------------------
------------------------------
----------------------- --------
######------------------ P ---------
-#########--------------- ----------
-##############-------------------------
-#################----------------------
-####################---------------------
-#######################------------------
--#########################---------------
--###########################-------------
-############# #############----------
--############ T ###############--------
--########### #################-----
--################################--
--################################
--############################
----#######################-
----#################-
--------------
Global CMT Convention Moment Tensor:
R T P
9.83e+21 -2.23e+22 1.55e+22
-2.23e+22 -6.20e+21 4.76e+21
1.55e+22 4.76e+21 -3.63e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.EU/20150706134216/index.html
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STK = 130
DIP = 10
RAKE = 95
MW = 4.24
HS = 25.0
The NDK file is 20150706134216.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2015/07/06 13:42:16:0 42.38 19.42 17.0 4.1 Montenegro
Stations used:
HT.THE HU.AMBH HU.BUD MN.BLY MN.DIVS MN.PDG MN.TIR MN.VTS
RO.BANR RO.BZS RO.DEV RO.LOT RO.PUNG SJ.BBLS SJ.FRGS
SL.CRES SL.KOGS
Filtering commands used:
cut o DIST/3.3 -30 o DIST/3.3 +70
rtr
taper w 0.1
hp c 0.02 n 3
lp c 0.06 n 3
Best Fitting Double Couple
Mo = 2.88e+22 dyne-cm
Mw = 4.24
Z = 25 km
Plane Strike Dip Rake
NP1 305 80 89
NP2 130 10 95
Principal Axes:
Axis Value Plunge Azimuth
T 2.88e+22 55 214
N 0.00e+00 1 305
P -2.88e+22 35 36
Moment Tensor: (dyne-cm)
Component Value
Mxx -6.20e+21
Mxy -4.76e+21
Mxz -2.23e+22
Myy -3.63e+21
Myz -1.55e+22
Mzz 9.83e+21
--------------
----------------------
----------------------------
------------------------------
----------------------- --------
######------------------ P ---------
-#########--------------- ----------
-##############-------------------------
-#################----------------------
-####################---------------------
-#######################------------------
--#########################---------------
--###########################-------------
-############# #############----------
--############ T ###############--------
--########### #################-----
--################################--
--################################
--############################
----#######################-
----#################-
--------------
Global CMT Convention Moment Tensor:
R T P
9.83e+21 -2.23e+22 1.55e+22
-2.23e+22 -6.20e+21 4.76e+21
1.55e+22 4.76e+21 -3.63e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.EU/20150706134216/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 o DIST/3.3 -30 o DIST/3.3 +70 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 1.0 110 45 -85 3.81 0.3032
WVFGRD96 2.0 110 40 -85 3.91 0.3621
WVFGRD96 3.0 100 40 -85 3.98 0.3528
WVFGRD96 4.0 295 60 -60 4.01 0.3033
WVFGRD96 5.0 305 80 -45 4.01 0.2784
WVFGRD96 6.0 100 90 -70 3.98 0.3091
WVFGRD96 7.0 285 85 70 3.99 0.3497
WVFGRD96 8.0 285 85 75 4.07 0.3773
WVFGRD96 9.0 295 80 80 4.09 0.4163
WVFGRD96 10.0 295 80 80 4.10 0.4502
WVFGRD96 11.0 295 80 80 4.10 0.4790
WVFGRD96 12.0 305 75 85 4.14 0.5056
WVFGRD96 13.0 305 75 85 4.14 0.5292
WVFGRD96 14.0 305 75 85 4.15 0.5484
WVFGRD96 15.0 305 75 85 4.16 0.5638
WVFGRD96 16.0 305 75 85 4.16 0.5765
WVFGRD96 17.0 305 75 85 4.17 0.5865
WVFGRD96 18.0 310 75 90 4.19 0.5944
WVFGRD96 19.0 310 75 90 4.20 0.6012
WVFGRD96 20.0 310 75 90 4.21 0.6061
WVFGRD96 21.0 305 80 85 4.21 0.6108
WVFGRD96 22.0 305 80 85 4.22 0.6141
WVFGRD96 23.0 125 10 90 4.22 0.6165
WVFGRD96 24.0 305 80 90 4.23 0.6178
WVFGRD96 25.0 130 10 95 4.24 0.6180
WVFGRD96 26.0 130 10 95 4.25 0.6171
WVFGRD96 27.0 135 10 100 4.26 0.6152
WVFGRD96 28.0 305 80 85 4.26 0.6123
WVFGRD96 29.0 145 10 110 4.27 0.6089
The best solution is
WVFGRD96 25.0 130 10 95 4.24 0.6180
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 o DIST/3.3 -30 o DIST/3.3 +70 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.
Should the national backbone of the USGS Advanced National Seismic System (ANSS) be implemented with an interstation separation of 300 km, it is very likely that an earthquake such as this would have been recorded at distances on the order of 100-200 km. This means that the closest station would have information on source depth and mechanism that was lacking here.
Dr. Harley Benz, USGS, provided the USGS USNSN digital data. The digital data used in this study were provided by Natural Resources Canada through their AUTODRM site http://www.seismo.nrcan.gc.ca/nwfa/autodrm/autodrm_req_e.php, and IRIS using their BUD interface.
Thanks also to the many seismic network operators whose dedication make this effort possible: University of Alaska, University of Washington, Oregon State University, University of Utah, Montana Bureas of Mines, UC Berkely, Caltech, UC San Diego, Saint L ouis University, Universityof Memphis, Lamont Doehrty Earth Observatory, Boston College, 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:
DATE=Mon Jul 6 14:04:00 CDT 2015