2014/12/24 22:41:19 43.71 21.67 10 3.8 NW Balkan
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2014/12/24 22:41:19:0 43.71 21.67 10.0 3.8 NW Balkan
Stations used:
BS.PLD HL.KEK HT.ALN HT.FNA HT.GRG HT.HORT HT.KNT HT.PAIG
HT.SOH HT.SRS MN.BLY MN.DIVS MN.PDG MN.TIR MN.VTS RO.BZS
RO.GZR RO.MDVR SJ.BBLS SJ.FRGS
Filtering commands used:
cut o DIST/3.3 -50 o DIST/3.3 +50
rtr
taper w 0.1
hp c 0.03 n 3
lp c 0.07 n 3
Best Fitting Double Couple
Mo = 5.89e+21 dyne-cm
Mw = 3.78
Z = 13 km
Plane Strike Dip Rake
NP1 214 76 154
NP2 310 65 15
Principal Axes:
Axis Value Plunge Azimuth
T 5.89e+21 28 170
N 0.00e+00 61 8
P -5.89e+21 8 264
Moment Tensor: (dyne-cm)
Component Value
Mxx 4.39e+21
Mxy -1.47e+21
Mxz -2.30e+21
Myy -5.56e+21
Myz 1.21e+21
Mzz 1.17e+21
##############
######################
#######################-----
######################--------
---------#############------------
--------------#######---------------
------------------###-----------------
--------------------##------------------
-------------------#####----------------
-------------------########---------------
-----------------############-------------
-------------###############-----------
P ------------#################----------
-----------####################-------
------------######################------
----------#######################-----
---------########################---
-------##########################-
----############ ###########
---############ T ##########
############ #######
##############
Global CMT Convention Moment Tensor:
R T P
1.17e+21 -2.30e+21 -1.21e+21
-2.30e+21 4.39e+21 1.47e+21
-1.21e+21 1.47e+21 -5.56e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.EU/20141224224119/index.html
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STK = 310
DIP = 65
RAKE = 15
MW = 3.78
HS = 13.0
The NDK file is 20141224224119.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2014/12/24 22:41:19:0 43.71 21.67 10.0 3.8 NW Balkan
Stations used:
BS.PLD HL.KEK HT.ALN HT.FNA HT.GRG HT.HORT HT.KNT HT.PAIG
HT.SOH HT.SRS MN.BLY MN.DIVS MN.PDG MN.TIR MN.VTS RO.BZS
RO.GZR RO.MDVR SJ.BBLS SJ.FRGS
Filtering commands used:
cut o DIST/3.3 -50 o DIST/3.3 +50
rtr
taper w 0.1
hp c 0.03 n 3
lp c 0.07 n 3
Best Fitting Double Couple
Mo = 5.89e+21 dyne-cm
Mw = 3.78
Z = 13 km
Plane Strike Dip Rake
NP1 214 76 154
NP2 310 65 15
Principal Axes:
Axis Value Plunge Azimuth
T 5.89e+21 28 170
N 0.00e+00 61 8
P -5.89e+21 8 264
Moment Tensor: (dyne-cm)
Component Value
Mxx 4.39e+21
Mxy -1.47e+21
Mxz -2.30e+21
Myy -5.56e+21
Myz 1.21e+21
Mzz 1.17e+21
##############
######################
#######################-----
######################--------
---------#############------------
--------------#######---------------
------------------###-----------------
--------------------##------------------
-------------------#####----------------
-------------------########---------------
-----------------############-------------
-------------###############-----------
P ------------#################----------
-----------####################-------
------------######################------
----------#######################-----
---------########################---
-------##########################-
----############ ###########
---############ T ##########
############ #######
##############
Global CMT Convention Moment Tensor:
R T P
1.17e+21 -2.30e+21 -1.21e+21
-2.30e+21 4.39e+21 1.47e+21
-1.21e+21 1.47e+21 -5.56e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.EU/20141224224119/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 -50 o DIST/3.3 +50 rtr taper w 0.1 hp c 0.03 n 3 lp c 0.07 n 3The results of this grid search from 0.5 to 19 km depth are as follow:
DEPTH STK DIP RAKE MW FIT
WVFGRD96 1.0 305 80 -10 3.39 0.3818
WVFGRD96 2.0 300 70 -20 3.50 0.4682
WVFGRD96 3.0 305 75 -15 3.54 0.5039
WVFGRD96 4.0 310 60 0 3.60 0.5342
WVFGRD96 5.0 310 60 5 3.62 0.5644
WVFGRD96 6.0 310 60 10 3.64 0.5950
WVFGRD96 7.0 310 60 10 3.66 0.6239
WVFGRD96 8.0 310 55 10 3.71 0.6505
WVFGRD96 9.0 310 60 15 3.73 0.6726
WVFGRD96 10.0 310 60 15 3.74 0.6891
WVFGRD96 11.0 310 60 15 3.75 0.6988
WVFGRD96 12.0 310 65 15 3.77 0.7049
WVFGRD96 13.0 310 65 15 3.78 0.7060
WVFGRD96 14.0 310 65 10 3.79 0.7023
WVFGRD96 15.0 305 65 10 3.80 0.6948
WVFGRD96 16.0 305 70 10 3.81 0.6858
WVFGRD96 17.0 305 70 10 3.82 0.6750
WVFGRD96 18.0 305 70 10 3.83 0.6616
WVFGRD96 19.0 305 70 10 3.84 0.6457
WVFGRD96 20.0 305 70 5 3.85 0.6281
WVFGRD96 21.0 305 70 -10 3.86 0.6103
WVFGRD96 22.0 305 70 -10 3.87 0.5920
WVFGRD96 23.0 300 70 -10 3.87 0.5728
WVFGRD96 24.0 300 70 -10 3.87 0.5536
WVFGRD96 25.0 300 70 -10 3.88 0.5335
WVFGRD96 26.0 300 70 -15 3.88 0.5135
WVFGRD96 27.0 300 70 -15 3.89 0.4934
WVFGRD96 28.0 300 70 -15 3.89 0.4730
WVFGRD96 29.0 300 70 -15 3.90 0.4532
The best solution is
WVFGRD96 13.0 310 65 15 3.78 0.7060
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 -50 o DIST/3.3 +50 rtr taper w 0.1 hp c 0.03 n 3 lp c 0.07 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=Thu Dec 25 15:49:31 CST 2014