The EMSC location is
2012/12/13 21:39:27 41.13 19.73 10.0 4.10 Albania
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2012/12/13 21:39:27:0 41.13 19.73 10.0 4.1 Albania
Stations used:
HL.KEK HT.AGG HT.FNA HT.GRG HT.HORT HT.KNT HT.LIT HT.SOH
HT.SRS HT.THE HT.XOR MN.BLY MN.DIVS MN.PDG MN.TIR MN.VTS
RO.BZS RO.DEV RO.LOT SJ.BBLS SJ.FRGS SL.BOJS SL.GCIS
SL.KOGS SL.SKDS
Filtering commands used:
hp c 0.02 n 3
lp c 0.06 n 3
Best Fitting Double Couple
Mo = 1.78e+22 dyne-cm
Mw = 4.10
Z = 26 km
Plane Strike Dip Rake
NP1 167 57 130
NP2 290 50 45
Principal Axes:
Axis Value Plunge Azimuth
T 1.78e+22 57 134
N 0.00e+00 33 323
P -1.78e+22 4 230
Moment Tensor: (dyne-cm)
Component Value
Mxx -4.74e+21
Mxy -1.14e+22
Mxz -4.82e+21
Myy -7.64e+21
Myz 6.85e+21
Mzz 1.24e+22
##------------
#####-----------------
#######---------------------
#######-----------------------
#########-------------------------
####-----##########-----------------
#---------###############-------------
-----------##################-----------
-----------#####################--------
------------#######################-------
------------#########################-----
-------------#########################----
-------------##########################---
-------------############ ###########-
-------------############ T ###########-
-------------########### ###########
-------------#######################
- ---------#####################
P ----------##################
------------###############
------------##########
----------####
Global CMT Convention Moment Tensor:
R T P
1.24e+22 -4.82e+21 -6.85e+21
-4.82e+21 -4.74e+21 1.14e+22
-6.85e+21 1.14e+22 -7.64e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.EU/20121213213927/index.html
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STK = 290
DIP = 50
RAKE = 45
MW = 4.10
HS = 26.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2012/12/13 21:39:27:0 41.13 19.73 10.0 4.1 Albania
Stations used:
HL.KEK HT.AGG HT.FNA HT.GRG HT.HORT HT.KNT HT.LIT HT.SOH
HT.SRS HT.THE HT.XOR MN.BLY MN.DIVS MN.PDG MN.TIR MN.VTS
RO.BZS RO.DEV RO.LOT SJ.BBLS SJ.FRGS SL.BOJS SL.GCIS
SL.KOGS SL.SKDS
Filtering commands used:
hp c 0.02 n 3
lp c 0.06 n 3
Best Fitting Double Couple
Mo = 1.78e+22 dyne-cm
Mw = 4.10
Z = 26 km
Plane Strike Dip Rake
NP1 167 57 130
NP2 290 50 45
Principal Axes:
Axis Value Plunge Azimuth
T 1.78e+22 57 134
N 0.00e+00 33 323
P -1.78e+22 4 230
Moment Tensor: (dyne-cm)
Component Value
Mxx -4.74e+21
Mxy -1.14e+22
Mxz -4.82e+21
Myy -7.64e+21
Myz 6.85e+21
Mzz 1.24e+22
##------------
#####-----------------
#######---------------------
#######-----------------------
#########-------------------------
####-----##########-----------------
#---------###############-------------
-----------##################-----------
-----------#####################--------
------------#######################-------
------------#########################-----
-------------#########################----
-------------##########################---
-------------############ ###########-
-------------############ T ###########-
-------------########### ###########
-------------#######################
- ---------#####################
P ----------##################
------------###############
------------##########
----------####
Global CMT Convention Moment Tensor:
R T P
1.24e+22 -4.82e+21 -6.85e+21
-4.82e+21 -4.74e+21 1.14e+22
-6.85e+21 1.14e+22 -7.64e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.EU/20121213213927/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:
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 0.5 335 45 -90 3.69 0.2918
WVFGRD96 1.0 155 45 -90 3.73 0.2870
WVFGRD96 2.0 155 45 -90 3.83 0.3603
WVFGRD96 3.0 40 45 -80 3.84 0.3508
WVFGRD96 4.0 50 80 -5 3.83 0.3266
WVFGRD96 5.0 50 80 0 3.87 0.3241
WVFGRD96 6.0 50 75 0 3.89 0.3144
WVFGRD96 7.0 50 70 5 3.91 0.3069
WVFGRD96 8.0 265 70 40 3.86 0.3104
WVFGRD96 9.0 270 70 45 3.88 0.3321
WVFGRD96 10.0 285 55 40 3.92 0.3614
WVFGRD96 11.0 290 50 45 3.95 0.3993
WVFGRD96 12.0 290 50 45 3.96 0.4379
WVFGRD96 13.0 295 45 50 3.99 0.4725
WVFGRD96 14.0 295 45 50 4.00 0.5030
WVFGRD96 15.0 295 45 50 4.01 0.5304
WVFGRD96 16.0 295 45 50 4.02 0.5527
WVFGRD96 17.0 295 45 50 4.03 0.5719
WVFGRD96 18.0 295 45 50 4.03 0.5886
WVFGRD96 19.0 295 45 50 4.04 0.6022
WVFGRD96 20.0 295 45 50 4.05 0.6145
WVFGRD96 21.0 295 45 50 4.06 0.6235
WVFGRD96 22.0 295 45 50 4.07 0.6312
WVFGRD96 23.0 295 45 50 4.08 0.6380
WVFGRD96 24.0 295 45 50 4.08 0.6422
WVFGRD96 25.0 290 50 45 4.09 0.6459
WVFGRD96 26.0 290 50 45 4.10 0.6476
WVFGRD96 27.0 290 50 45 4.11 0.6473
WVFGRD96 28.0 290 50 45 4.11 0.6461
WVFGRD96 29.0 290 50 45 4.12 0.6434
WVFGRD96 30.0 290 50 45 4.13 0.6394
WVFGRD96 31.0 290 50 45 4.13 0.6343
WVFGRD96 32.0 290 50 45 4.14 0.6278
WVFGRD96 33.0 290 50 45 4.15 0.6204
WVFGRD96 34.0 110 50 45 4.16 0.6138
WVFGRD96 35.0 110 50 45 4.17 0.6052
WVFGRD96 36.0 110 50 45 4.18 0.5965
WVFGRD96 37.0 110 50 45 4.19 0.5873
WVFGRD96 38.0 110 50 45 4.20 0.5763
WVFGRD96 39.0 110 50 45 4.21 0.5648
WVFGRD96 40.0 120 50 50 4.32 0.5697
WVFGRD96 41.0 120 50 50 4.33 0.5642
WVFGRD96 42.0 120 50 50 4.33 0.5566
WVFGRD96 43.0 120 50 55 4.33 0.5483
WVFGRD96 44.0 120 50 55 4.34 0.5394
WVFGRD96 45.0 120 50 55 4.35 0.5294
WVFGRD96 46.0 120 50 55 4.35 0.5188
WVFGRD96 47.0 120 55 55 4.36 0.5076
WVFGRD96 48.0 120 55 55 4.37 0.4967
WVFGRD96 49.0 125 55 65 4.37 0.4853
The best solution is
WVFGRD96 26.0 290 50 45 4.10 0.6476
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
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=Thu Dec 13 20:03:00 CST 2012