2012/11/27 19:06:21 40.787 19.661 18.8 4.45 Albania
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2012/11/27 19:06:21:0 40.79 19.66 18.8 4.4 Albania
Stations used:
HL.ITM HL.KEK HT.AGG HT.FNA HT.GRG HT.HORT HT.KNT HT.LIT
HT.LKD2 HT.SOH HT.SRS HT.THE MN.DIVS MN.PDG MN.TIR RO.BZS
RO.LOT SJ.BBLS SJ.FRGS
Filtering commands used:
hp c 0.02 n 3
lp c 0.06 n 3
Best Fitting Double Couple
Mo = 9.55e+21 dyne-cm
Mw = 3.92
Z = 21 km
Plane Strike Dip Rake
NP1 150 70 65
NP2 24 32 139
Principal Axes:
Axis Value Plunge Azimuth
T 9.55e+21 58 26
N 0.00e+00 23 159
P -9.55e+21 21 259
Moment Tensor: (dyne-cm)
Component Value
Mxx 1.89e+21
Mxy -5.13e+20
Mxz 4.51e+21
Myy -7.46e+21
Myz 5.05e+21
Mzz 5.56e+21
##############
-####################-
----#####################---
-----#######################--
-------#######################----
--------########################----
----------########### ##########----
-----------########### T ##########-----
------------########## ##########-----
--------------######################------
---------------#####################------
--- ----------####################------
--- P -----------##################-------
-- ------------#################------
------------------###############-------
------------------#############-------
-------------------##########-------
--------------------######--------
-------------------###--------
-------------------##-------
------------#########-
##############
Global CMT Convention Moment Tensor:
R T P
5.56e+21 4.51e+21 -5.05e+21
4.51e+21 1.89e+21 5.13e+20
-5.05e+21 5.13e+20 -7.46e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.EU/20121127190621/index.html
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STK = 150
DIP = 70
RAKE = 65
MW = 3.92
HS = 21.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2012/11/27 19:06:21:0 40.79 19.66 18.8 4.4 Albania
Stations used:
HL.ITM HL.KEK HT.AGG HT.FNA HT.GRG HT.HORT HT.KNT HT.LIT
HT.LKD2 HT.SOH HT.SRS HT.THE MN.DIVS MN.PDG MN.TIR RO.BZS
RO.LOT SJ.BBLS SJ.FRGS
Filtering commands used:
hp c 0.02 n 3
lp c 0.06 n 3
Best Fitting Double Couple
Mo = 9.55e+21 dyne-cm
Mw = 3.92
Z = 21 km
Plane Strike Dip Rake
NP1 150 70 65
NP2 24 32 139
Principal Axes:
Axis Value Plunge Azimuth
T 9.55e+21 58 26
N 0.00e+00 23 159
P -9.55e+21 21 259
Moment Tensor: (dyne-cm)
Component Value
Mxx 1.89e+21
Mxy -5.13e+20
Mxz 4.51e+21
Myy -7.46e+21
Myz 5.05e+21
Mzz 5.56e+21
##############
-####################-
----#####################---
-----#######################--
-------#######################----
--------########################----
----------########### ##########----
-----------########### T ##########-----
------------########## ##########-----
--------------######################------
---------------#####################------
--- ----------####################------
--- P -----------##################-------
-- ------------#################------
------------------###############-------
------------------#############-------
-------------------##########-------
--------------------######--------
-------------------###--------
-------------------##-------
------------#########-
##############
Global CMT Convention Moment Tensor:
R T P
5.56e+21 4.51e+21 -5.05e+21
4.51e+21 1.89e+21 5.13e+20
-5.05e+21 5.13e+20 -7.46e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.EU/20121127190621/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 0.5 320 60 5 3.50 0.2795
WVFGRD96 1.0 320 75 5 3.51 0.2995
WVFGRD96 2.0 320 70 10 3.62 0.3554
WVFGRD96 3.0 315 90 5 3.66 0.3724
WVFGRD96 4.0 315 90 10 3.70 0.3592
WVFGRD96 5.0 315 90 10 3.72 0.3345
WVFGRD96 6.0 140 60 15 3.75 0.3137
WVFGRD96 7.0 145 85 60 3.72 0.3182
WVFGRD96 8.0 150 80 70 3.80 0.3422
WVFGRD96 9.0 150 80 70 3.81 0.3742
WVFGRD96 10.0 150 80 75 3.81 0.4026
WVFGRD96 11.0 155 75 75 3.84 0.4287
WVFGRD96 12.0 150 75 75 3.83 0.4501
WVFGRD96 13.0 150 75 70 3.85 0.4712
WVFGRD96 14.0 150 75 70 3.85 0.4880
WVFGRD96 15.0 150 75 70 3.86 0.5011
WVFGRD96 16.0 150 75 70 3.87 0.5135
WVFGRD96 17.0 150 70 70 3.88 0.5215
WVFGRD96 18.0 150 70 70 3.88 0.5297
WVFGRD96 19.0 150 70 65 3.90 0.5344
WVFGRD96 20.0 150 70 65 3.90 0.5367
WVFGRD96 21.0 150 70 65 3.92 0.5410
WVFGRD96 22.0 150 70 60 3.93 0.5397
WVFGRD96 23.0 145 75 60 3.93 0.5390
WVFGRD96 24.0 145 75 60 3.93 0.5370
WVFGRD96 25.0 145 75 60 3.94 0.5335
WVFGRD96 26.0 150 70 55 3.96 0.5297
WVFGRD96 27.0 150 70 55 3.97 0.5242
WVFGRD96 28.0 150 70 55 3.97 0.5186
WVFGRD96 29.0 150 70 50 3.98 0.5122
The best solution is
WVFGRD96 21.0 150 70 65 3.92 0.5410
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=Tue Nov 27 16:33:34 CST 2012