2014/06/24 19:39:53 43.79 24.47 7 4.2 Bulgaria
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2014/06/24 19:39:53:9 43.79 24.47 7.0 4.2 Bulgaria
Stations used:
BS.PLD GE.TIRR HT.ALN HT.GRG HT.HORT HT.KNT HT.PAIG HT.SIGR
HT.SRS HT.THE HU.BUD HU.TRPA MN.BLY MN.PDG MN.TIR MN.VTS
RO.BZS RO.CFR SJ.BBLS SJ.FRGS
Filtering commands used:
cut o DIST/3.3 -40 o DIST/3.3 +90
rtr
taper w 0.1
hp c 0.02 n 3
lp c 0.05 n 3
Best Fitting Double Couple
Mo = 7.76e+21 dyne-cm
Mw = 3.86
Z = 11 km
Plane Strike Dip Rake
NP1 224 85 170
NP2 315 80 5
Principal Axes:
Axis Value Plunge Azimuth
T 7.76e+21 11 179
N 0.00e+00 79 18
P -7.76e+21 4 270
Moment Tensor: (dyne-cm)
Component Value
Mxx 7.50e+21
Mxy -1.16e+20
Mxz -1.40e+21
Myy -7.73e+21
Myz 5.00e+20
Mzz 2.31e+20
##############
######################
############################
--##########################--
-------#####################------
----------#################---------
--------------############------------
-----------------########---------------
-------------------####-----------------
------------------------------------------
------------------####------------------
P ----------------#######-----------------
---------------##########---------------
--------------##############------------
------------#################-----------
----------####################--------
-------#######################------
-----#########################----
-############################-
############################
########## #########
###### T #####
Global CMT Convention Moment Tensor:
R T P
2.31e+20 -1.40e+21 -5.00e+20
-1.40e+21 7.50e+21 1.16e+20
-5.00e+20 1.16e+20 -7.73e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.EU/20140624193953/index.html
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STK = 315
DIP = 80
RAKE = 5
MW = 3.86
HS = 11.0
The NDK file is 20140624193953.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2014/06/24 19:39:53:9 43.79 24.47 7.0 4.2 Bulgaria
Stations used:
BS.PLD GE.TIRR HT.ALN HT.GRG HT.HORT HT.KNT HT.PAIG HT.SIGR
HT.SRS HT.THE HU.BUD HU.TRPA MN.BLY MN.PDG MN.TIR MN.VTS
RO.BZS RO.CFR SJ.BBLS SJ.FRGS
Filtering commands used:
cut o DIST/3.3 -40 o DIST/3.3 +90
rtr
taper w 0.1
hp c 0.02 n 3
lp c 0.05 n 3
Best Fitting Double Couple
Mo = 7.76e+21 dyne-cm
Mw = 3.86
Z = 11 km
Plane Strike Dip Rake
NP1 224 85 170
NP2 315 80 5
Principal Axes:
Axis Value Plunge Azimuth
T 7.76e+21 11 179
N 0.00e+00 79 18
P -7.76e+21 4 270
Moment Tensor: (dyne-cm)
Component Value
Mxx 7.50e+21
Mxy -1.16e+20
Mxz -1.40e+21
Myy -7.73e+21
Myz 5.00e+20
Mzz 2.31e+20
##############
######################
############################
--##########################--
-------#####################------
----------#################---------
--------------############------------
-----------------########---------------
-------------------####-----------------
------------------------------------------
------------------####------------------
P ----------------#######-----------------
---------------##########---------------
--------------##############------------
------------#################-----------
----------####################--------
-------#######################------
-----#########################----
-############################-
############################
########## #########
###### T #####
Global CMT Convention Moment Tensor:
R T P
2.31e+20 -1.40e+21 -5.00e+20
-1.40e+21 7.50e+21 1.16e+20
-5.00e+20 1.16e+20 -7.73e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.EU/20140624193953/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 -40 o DIST/3.3 +90 rtr taper w 0.1 hp c 0.02 n 3 lp c 0.05 n 3The results of this grid search from 0.5 to 19 km depth are as follow:
DEPTH STK DIP RAKE MW FIT
WVFGRD96 1.0 315 80 15 3.60 0.3846
WVFGRD96 2.0 315 75 10 3.68 0.4640
WVFGRD96 3.0 315 75 10 3.71 0.5012
WVFGRD96 4.0 315 75 5 3.73 0.5303
WVFGRD96 5.0 315 85 0 3.75 0.5542
WVFGRD96 6.0 315 85 0 3.77 0.5745
WVFGRD96 7.0 315 85 0 3.79 0.5919
WVFGRD96 8.0 315 80 5 3.82 0.6075
WVFGRD96 9.0 315 80 5 3.83 0.6157
WVFGRD96 10.0 315 80 5 3.85 0.6208
WVFGRD96 11.0 315 80 5 3.86 0.6234
WVFGRD96 12.0 135 90 -5 3.87 0.6196
WVFGRD96 13.0 315 75 5 3.89 0.6233
WVFGRD96 14.0 315 75 5 3.90 0.6222
WVFGRD96 15.0 315 90 -10 3.90 0.6210
WVFGRD96 16.0 315 90 -10 3.91 0.6224
WVFGRD96 17.0 315 90 -10 3.92 0.6224
WVFGRD96 18.0 315 90 -10 3.93 0.6211
WVFGRD96 19.0 315 90 -10 3.94 0.6190
WVFGRD96 20.0 315 90 -5 3.95 0.6157
WVFGRD96 21.0 315 90 -5 3.96 0.6112
WVFGRD96 22.0 315 90 -5 3.97 0.6056
WVFGRD96 23.0 315 90 -5 3.98 0.5987
WVFGRD96 24.0 315 90 -5 3.98 0.5906
WVFGRD96 25.0 315 90 -5 3.99 0.5816
WVFGRD96 26.0 315 90 -5 4.00 0.5716
WVFGRD96 27.0 315 90 -5 4.00 0.5610
WVFGRD96 28.0 315 90 -5 4.01 0.5499
WVFGRD96 29.0 315 90 -5 4.02 0.5382
The best solution is
WVFGRD96 11.0 315 80 5 3.86 0.6234
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 -40 o DIST/3.3 +90 rtr taper w 0.1 hp c 0.02 n 3 lp c 0.05 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. |
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=Wed Jun 25 04:01:29 CDT 2014