2013/05/15 15:02:42 41.41 19.44 10.0 3.80 Albania
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2013/05/15 15:02:42:0 41.41 19.44 10.0 3.8 Albania
Stations used:
HT.AGG HT.FNA HT.GRG HT.HORT HT.KNT HT.SOH HT.SRS HT.THE
MN.BLY MN.PDG MN.TIR MN.VTS RO.BZS SJ.BBLS SJ.FRGS
Filtering commands used:
hp c 0.02 n 3
lp c 0.06 n 3
Best Fitting Double Couple
Mo = 8.04e+21 dyne-cm
Mw = 3.87
Z = 25 km
Plane Strike Dip Rake
NP1 8 62 139
NP2 120 55 35
Principal Axes:
Axis Value Plunge Azimuth
T 8.04e+21 48 331
N 0.00e+00 42 159
P -8.04e+21 4 66
Moment Tensor: (dyne-cm)
Component Value
Mxx 1.42e+21
Mxy -4.57e+21
Mxz 3.25e+21
Myy -5.75e+21
Myz -2.48e+21
Mzz 4.33e+21
###########---
################------
####################--------
#####################---------
########## ###########----------
########### T ###########----------
-########### ###########---------- P
---########################----------
----#######################-------------
------######################--------------
-------#####################--------------
--------####################--------------
----------##################--------------
-----------###############--------------
--------------############--------------
----------------########--------------
-------------------####-------------
---------------------#############
------------------############
----------------############
-----------###########
-----#########
Global CMT Convention Moment Tensor:
R T P
4.33e+21 3.25e+21 2.48e+21
3.25e+21 1.42e+21 4.57e+21
2.48e+21 4.57e+21 -5.75e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.EU/20130515150242/index.html
|
STK = 120
DIP = 55
RAKE = 35
MW = 3.87
HS = 25.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2013/05/15 15:02:42:0 41.41 19.44 10.0 3.8 Albania
Stations used:
HT.AGG HT.FNA HT.GRG HT.HORT HT.KNT HT.SOH HT.SRS HT.THE
MN.BLY MN.PDG MN.TIR MN.VTS RO.BZS SJ.BBLS SJ.FRGS
Filtering commands used:
hp c 0.02 n 3
lp c 0.06 n 3
Best Fitting Double Couple
Mo = 8.04e+21 dyne-cm
Mw = 3.87
Z = 25 km
Plane Strike Dip Rake
NP1 8 62 139
NP2 120 55 35
Principal Axes:
Axis Value Plunge Azimuth
T 8.04e+21 48 331
N 0.00e+00 42 159
P -8.04e+21 4 66
Moment Tensor: (dyne-cm)
Component Value
Mxx 1.42e+21
Mxy -4.57e+21
Mxz 3.25e+21
Myy -5.75e+21
Myz -2.48e+21
Mzz 4.33e+21
###########---
################------
####################--------
#####################---------
########## ###########----------
########### T ###########----------
-########### ###########---------- P
---########################----------
----#######################-------------
------######################--------------
-------#####################--------------
--------####################--------------
----------##################--------------
-----------###############--------------
--------------############--------------
----------------########--------------
-------------------####-------------
---------------------#############
------------------############
----------------############
-----------###########
-----#########
Global CMT Convention Moment Tensor:
R T P
4.33e+21 3.25e+21 2.48e+21
3.25e+21 1.42e+21 4.57e+21
2.48e+21 4.57e+21 -5.75e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.EU/20130515150242/index.html
|
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.
|
|
|
|
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 45 40 -95 3.37 0.2580
WVFGRD96 1.0 130 90 5 3.41 0.2769
WVFGRD96 2.0 130 85 10 3.52 0.3682
WVFGRD96 3.0 310 90 -5 3.58 0.4243
WVFGRD96 4.0 130 85 5 3.62 0.4490
WVFGRD96 5.0 130 85 0 3.65 0.4529
WVFGRD96 6.0 125 85 0 3.66 0.4522
WVFGRD96 7.0 125 80 5 3.68 0.4566
WVFGRD96 8.0 125 75 5 3.71 0.4595
WVFGRD96 9.0 110 45 5 3.70 0.4735
WVFGRD96 10.0 110 45 10 3.71 0.4957
WVFGRD96 11.0 115 45 20 3.73 0.5171
WVFGRD96 12.0 115 45 25 3.74 0.5361
WVFGRD96 13.0 115 50 25 3.75 0.5540
WVFGRD96 14.0 115 50 25 3.76 0.5696
WVFGRD96 15.0 115 50 25 3.77 0.5817
WVFGRD96 16.0 120 50 35 3.80 0.5920
WVFGRD96 17.0 120 50 35 3.80 0.6021
WVFGRD96 18.0 120 50 35 3.81 0.6107
WVFGRD96 19.0 120 50 35 3.82 0.6163
WVFGRD96 20.0 120 55 35 3.84 0.6212
WVFGRD96 21.0 120 55 35 3.85 0.6262
WVFGRD96 22.0 120 55 35 3.85 0.6288
WVFGRD96 23.0 120 55 35 3.86 0.6321
WVFGRD96 24.0 120 55 35 3.86 0.6326
WVFGRD96 25.0 120 55 35 3.87 0.6339
WVFGRD96 26.0 120 55 30 3.88 0.6332
WVFGRD96 27.0 120 55 30 3.88 0.6332
WVFGRD96 28.0 120 55 30 3.89 0.6311
WVFGRD96 29.0 120 55 30 3.89 0.6295
WVFGRD96 30.0 120 60 35 3.90 0.6267
WVFGRD96 31.0 120 60 30 3.91 0.6266
WVFGRD96 32.0 120 60 30 3.92 0.6239
WVFGRD96 33.0 120 60 30 3.92 0.6219
WVFGRD96 34.0 120 60 30 3.93 0.6180
WVFGRD96 35.0 120 60 25 3.94 0.6134
WVFGRD96 36.0 120 60 25 3.94 0.6089
WVFGRD96 37.0 120 60 25 3.95 0.6019
WVFGRD96 38.0 120 65 25 3.97 0.5967
WVFGRD96 39.0 120 65 20 3.98 0.5928
WVFGRD96 40.0 125 60 35 4.06 0.6011
WVFGRD96 41.0 125 60 40 4.06 0.5998
WVFGRD96 42.0 125 60 35 4.07 0.5947
WVFGRD96 43.0 125 60 35 4.08 0.5917
WVFGRD96 44.0 125 60 35 4.08 0.5857
WVFGRD96 45.0 125 60 35 4.09 0.5815
WVFGRD96 46.0 125 60 35 4.09 0.5755
WVFGRD96 47.0 125 60 35 4.10 0.5702
WVFGRD96 48.0 125 60 35 4.10 0.5645
WVFGRD96 49.0 125 60 35 4.11 0.5580
The best solution is
WVFGRD96 25.0 120 55 35 3.87 0.6339
The mechanism correspond to the best fit is
|
|
|
The best fit as a function of depth is given in the following figure:
|
|
|
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
|
|
|
|
| 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 May 16 00:06:07 CDT 2013