Location
2012/11/12 23:18:42 42.558 19.021 14.0 4.60 Montenegro
Arrival Times (from USGS)
Arrival time list
Felt Map
USGS Felt map for this earthquake
USGS Felt reports archive
Focal Mechanism
USGS/SLU Moment Tensor Solution
ENS 2012/11/12 23:18:42:5 42.56 19.02 14.0 4.6 Montenegro
Stations used:
HT.AGG HT.FNA HT.GRG HU.BUD MN.BLY MN.DIVS MN.PDG MN.TIR
MN.TRI MN.VTS RO.BZS RO.DEV RO.VOIR SJ.BBLS SJ.FRGS
Filtering commands used:
hp c 0.02 n 3
lp c 0.06 n 3
Best Fitting Double Couple
Mo = 5.37e+22 dyne-cm
Mw = 4.42
Z = 26 km
Plane Strike Dip Rake
NP1 109 55 87
NP2 295 35 95
Principal Axes:
Axis Value Plunge Azimuth
T 5.37e+22 80 5
N 0.00e+00 3 111
P -5.37e+22 10 201
Moment Tensor: (dyne-cm)
Component Value
Mxx -4.33e+22
Mxy -1.75e+22
Mxz 1.82e+22
Myy -6.92e+21
Myz 4.26e+21
Mzz 5.03e+22
--------------
----------------------
----------------------------
-----###########--------------
--#####################-----------
-##########################---------
###############################-------
##################################------
-################## #############-----
---################# T ##############-----
----################ ###############----
------#################################---
--------###############################---
----------#############################-
-------------##########################-
----------------####################--
------------------------------------
----------------------------------
------------------------------
------ -------------------
--- P ----------------
------------
Global CMT Convention Moment Tensor:
R T P
5.03e+22 1.82e+22 -4.26e+21
1.82e+22 -4.33e+22 1.75e+22
-4.26e+21 1.75e+22 -6.92e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.EU/20121112231842/index.html
|
Preferred Solution
The preferred solution from an analysis of the surface-wave spectral amplitude radiation pattern, waveform inversion and first motion observations is
STK = 295
DIP = 35
RAKE = 95
MW = 4.42
HS = 26.0
The waveform inversion is preferred.
Moment Tensor Comparison
The following compares this source inversion to others
| SLU |
USGSMT |
USGS/SLU Moment Tensor Solution
ENS 2012/11/12 23:18:42:5 42.56 19.02 14.0 4.6 Montenegro
Stations used:
HT.AGG HT.FNA HT.GRG HU.BUD MN.BLY MN.DIVS MN.PDG MN.TIR
MN.TRI MN.VTS RO.BZS RO.DEV RO.VOIR SJ.BBLS SJ.FRGS
Filtering commands used:
hp c 0.02 n 3
lp c 0.06 n 3
Best Fitting Double Couple
Mo = 5.37e+22 dyne-cm
Mw = 4.42
Z = 26 km
Plane Strike Dip Rake
NP1 109 55 87
NP2 295 35 95
Principal Axes:
Axis Value Plunge Azimuth
T 5.37e+22 80 5
N 0.00e+00 3 111
P -5.37e+22 10 201
Moment Tensor: (dyne-cm)
Component Value
Mxx -4.33e+22
Mxy -1.75e+22
Mxz 1.82e+22
Myy -6.92e+21
Myz 4.26e+21
Mzz 5.03e+22
--------------
----------------------
----------------------------
-----###########--------------
--#####################-----------
-##########################---------
###############################-------
##################################------
-################## #############-----
---################# T ##############-----
----################ ###############----
------#################################---
--------###############################---
----------#############################-
-------------##########################-
----------------####################--
------------------------------------
----------------------------------
------------------------------
------ -------------------
--- P ----------------
------------
Global CMT Convention Moment Tensor:
R T P
5.03e+22 1.82e+22 -4.26e+21
1.82e+22 -4.33e+22 1.75e+22
-4.26e+21 1.75e+22 -6.92e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.EU/20121112231842/index.html
|
USGS/SLU Regional Moment Solution
MONTENEGRO
12/11/12 23:18:42.63
Epicenter: 42.587 19.018
MW 4.4
USGS/SLU REGIONAL MOMENT TENSOR
Depth 25 No. of sta: 19
Moment Tensor; Scale 10**15 Nm
Mrr= 5.70 Mtt=-4.76
Mpp=-0.93 Mrt= 0.63
Mrp=-1.20 Mtp= 2.13
Principal axes:
T Val= 5.91 Plg=80 Azm= 81
N -0.10 8 296
P -5.81 5 205
Best Double Couple:Mo=5.9*10**15
NP1:Strike=286 Dip=40 Slip= 78
NP2: 122 51 100
|
Waveform Inversion
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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Location of broadband stations used for waveform inversion
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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 3
The results of this grid search from 0.5 to 19 km depth are as follow:
DEPTH STK DIP RAKE MW FIT
WVFGRD96 0.5 290 45 -90 4.03 0.3185
WVFGRD96 1.0 110 45 -90 4.06 0.3047
WVFGRD96 2.0 110 50 -90 4.17 0.3810
WVFGRD96 3.0 280 40 -85 4.21 0.3597
WVFGRD96 4.0 275 40 -90 4.22 0.2883
WVFGRD96 5.0 155 40 -10 4.15 0.2690
WVFGRD96 6.0 160 40 5 4.15 0.2876
WVFGRD96 7.0 165 40 15 4.16 0.3105
WVFGRD96 8.0 160 30 0 4.23 0.3253
WVFGRD96 9.0 165 30 10 4.23 0.3497
WVFGRD96 10.0 85 75 70 4.27 0.3864
WVFGRD96 11.0 90 70 70 4.30 0.4277
WVFGRD96 12.0 90 70 70 4.30 0.4678
WVFGRD96 13.0 95 65 75 4.33 0.5062
WVFGRD96 14.0 95 60 70 4.35 0.5396
WVFGRD96 15.0 95 60 70 4.35 0.5702
WVFGRD96 16.0 100 60 75 4.36 0.5956
WVFGRD96 17.0 100 60 75 4.37 0.6161
WVFGRD96 18.0 100 60 75 4.37 0.6324
WVFGRD96 19.0 100 55 75 4.38 0.6459
WVFGRD96 20.0 100 55 75 4.39 0.6568
WVFGRD96 21.0 105 55 80 4.40 0.6644
WVFGRD96 22.0 105 55 80 4.41 0.6703
WVFGRD96 23.0 105 55 80 4.41 0.6750
WVFGRD96 24.0 105 55 80 4.41 0.6776
WVFGRD96 25.0 105 55 85 4.41 0.6789
WVFGRD96 26.0 295 35 95 4.42 0.6790
WVFGRD96 27.0 110 55 90 4.43 0.6778
WVFGRD96 28.0 110 50 90 4.43 0.6761
WVFGRD96 29.0 110 50 90 4.44 0.6737
WVFGRD96 30.0 115 50 95 4.45 0.6698
WVFGRD96 31.0 290 40 85 4.46 0.6654
WVFGRD96 32.0 115 50 95 4.46 0.6598
WVFGRD96 33.0 115 50 95 4.47 0.6538
WVFGRD96 34.0 285 40 80 4.48 0.6467
WVFGRD96 35.0 285 40 80 4.49 0.6394
WVFGRD96 36.0 285 40 80 4.50 0.6308
WVFGRD96 37.0 285 40 80 4.51 0.6224
WVFGRD96 38.0 285 40 75 4.53 0.6131
WVFGRD96 39.0 285 40 75 4.55 0.6034
The best solution is
WVFGRD96 26.0 295 35 95 4.42 0.6790
The mechanism correspond to the best fit is
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Figure 1. Waveform inversion focal mechanism
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The best fit as a function of depth is given in the following figure:
|
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Figure 2. Depth sensitivity for waveform mechanism
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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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Figure 3. Waveform comparison for selected depth
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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.
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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:
- The origin time and epicentral distance are incorrect
- The velocity model used for the inversion is incorrect
- The velocity model used to define the P-arrival time is not the
same as the velocity model used for the waveform inversion
(assuming that the initial trace alignment is based on the
P arrival time)
Assuming only a mislocation, the time shifts are fit to a functional form:
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.
Discussion
The Future
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.
Acknowledgements
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.
Velocity Model
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
Quality Control
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 13 07:42:58 CST 2012
Last Changed 2012/11/12