2014/03/08 17:32:50 41.51 19.42 10.0 4.0 Albania
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2014/03/08 17:32:50:0 41.51 19.42 10.0 4.0 Albania
Stations used:
HT.ALN HT.GRG HT.KNT HT.LIT HT.SRS HT.THE MN.PDG MN.TIR
SJ.BBLS
Filtering commands used:
cut a -20 a 180
rtr
taper w 0.1
hp c 0.02 n 3
lp c 0.06 n 3
Best Fitting Double Couple
Mo = 6.76e+21 dyne-cm
Mw = 3.82
Z = 27 km
Plane Strike Dip Rake
NP1 145 60 85
NP2 335 30 99
Principal Axes:
Axis Value Plunge Azimuth
T 6.76e+21 74 42
N 0.00e+00 4 147
P -6.76e+21 15 239
Moment Tensor: (dyne-cm)
Component Value
Mxx -1.44e+21
Mxy -2.57e+21
Mxz 2.17e+21
Myy -4.39e+21
Myz 2.59e+21
Mzz 5.83e+21
--------------
############----------
--#################---------
---###################--------
-----#####################--------
------#######################-------
-------########################-------
---------########################-------
---------############ ##########------
-----------########### T ###########------
------------########## ###########------
-------------#######################------
--------------######################------
--------------#####################-----
--- ---------####################-----
-- P -----------##################----
- -------------###############----
------------------#############---
------------------##########--
---------------------#####--
---------------------#
--------------
Global CMT Convention Moment Tensor:
R T P
5.83e+21 2.17e+21 -2.59e+21
2.17e+21 -1.44e+21 2.57e+21
-2.59e+21 2.57e+21 -4.39e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.EU/20140308173250/index.html
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STK = 145
DIP = 60
RAKE = 85
MW = 3.82
HS = 27.0
The NDK file is 20140308173250.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2014/03/08 17:32:50:0 41.51 19.42 10.0 4.0 Albania
Stations used:
HT.ALN HT.GRG HT.KNT HT.LIT HT.SRS HT.THE MN.PDG MN.TIR
SJ.BBLS
Filtering commands used:
cut a -20 a 180
rtr
taper w 0.1
hp c 0.02 n 3
lp c 0.06 n 3
Best Fitting Double Couple
Mo = 6.76e+21 dyne-cm
Mw = 3.82
Z = 27 km
Plane Strike Dip Rake
NP1 145 60 85
NP2 335 30 99
Principal Axes:
Axis Value Plunge Azimuth
T 6.76e+21 74 42
N 0.00e+00 4 147
P -6.76e+21 15 239
Moment Tensor: (dyne-cm)
Component Value
Mxx -1.44e+21
Mxy -2.57e+21
Mxz 2.17e+21
Myy -4.39e+21
Myz 2.59e+21
Mzz 5.83e+21
--------------
############----------
--#################---------
---###################--------
-----#####################--------
------#######################-------
-------########################-------
---------########################-------
---------############ ##########------
-----------########### T ###########------
------------########## ###########------
-------------#######################------
--------------######################------
--------------#####################-----
--- ---------####################-----
-- P -----------##################----
- -------------###############----
------------------#############---
------------------##########--
---------------------#####--
---------------------#
--------------
Global CMT Convention Moment Tensor:
R T P
5.83e+21 2.17e+21 -2.59e+21
2.17e+21 -1.44e+21 2.57e+21
-2.59e+21 2.57e+21 -4.39e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.EU/20140308173250/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 a -20 a 180 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 50 90 10 3.28 0.1310
WVFGRD96 2.0 225 75 -25 3.42 0.1774
WVFGRD96 3.0 50 90 5 3.46 0.2010
WVFGRD96 4.0 50 85 0 3.50 0.2128
WVFGRD96 5.0 50 90 0 3.53 0.2153
WVFGRD96 6.0 230 90 5 3.55 0.2142
WVFGRD96 7.0 50 85 -5 3.57 0.2140
WVFGRD96 8.0 50 90 -15 3.61 0.2154
WVFGRD96 9.0 230 90 20 3.63 0.2158
WVFGRD96 10.0 50 90 -20 3.64 0.2163
WVFGRD96 11.0 10 65 -50 3.62 0.2244
WVFGRD96 12.0 10 60 -50 3.65 0.2299
WVFGRD96 13.0 10 60 -50 3.65 0.2342
WVFGRD96 14.0 10 60 -50 3.66 0.2377
WVFGRD96 15.0 240 60 45 3.73 0.2404
WVFGRD96 16.0 240 55 40 3.76 0.2476
WVFGRD96 17.0 240 55 40 3.77 0.2534
WVFGRD96 18.0 240 55 40 3.78 0.2585
WVFGRD96 19.0 240 55 40 3.79 0.2628
WVFGRD96 20.0 240 55 40 3.80 0.2664
WVFGRD96 21.0 240 60 45 3.79 0.2682
WVFGRD96 22.0 240 60 45 3.80 0.2705
WVFGRD96 23.0 140 60 75 3.79 0.2721
WVFGRD96 24.0 145 60 80 3.80 0.2742
WVFGRD96 25.0 145 60 85 3.81 0.2766
WVFGRD96 26.0 335 30 100 3.82 0.2777
WVFGRD96 27.0 145 60 85 3.82 0.2784
WVFGRD96 28.0 145 75 100 3.86 0.2781
WVFGRD96 29.0 145 75 100 3.87 0.2781
WVFGRD96 30.0 145 75 100 3.87 0.2774
WVFGRD96 31.0 290 20 55 3.88 0.2758
WVFGRD96 32.0 300 20 65 3.87 0.2730
WVFGRD96 33.0 300 20 65 3.88 0.2700
WVFGRD96 34.0 285 20 50 3.88 0.2672
WVFGRD96 35.0 275 20 40 3.88 0.2635
WVFGRD96 36.0 135 60 85 3.85 0.2620
WVFGRD96 37.0 320 30 95 3.86 0.2595
WVFGRD96 38.0 305 30 85 3.89 0.2566
WVFGRD96 39.0 305 30 85 3.89 0.2541
WVFGRD96 40.0 245 20 15 4.04 0.2455
WVFGRD96 41.0 245 20 15 4.05 0.2431
WVFGRD96 42.0 245 20 15 4.05 0.2399
WVFGRD96 43.0 250 20 15 4.03 0.2370
WVFGRD96 44.0 250 20 15 4.04 0.2341
WVFGRD96 45.0 125 65 95 4.02 0.2326
WVFGRD96 46.0 300 25 85 4.01 0.2305
WVFGRD96 47.0 130 65 90 4.00 0.2280
WVFGRD96 48.0 130 65 90 4.00 0.2259
WVFGRD96 49.0 130 65 90 4.00 0.2234
The best solution is
WVFGRD96 27.0 145 60 85 3.82 0.2784
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 a -20 a 180 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=Sat Mar 8 18:01:14 CST 2014