Location
2012/07/27 23:12:22 44.20 17.92 2.0 4.70 Boznia-Herzegovina
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 2012/07/27 23:12:22:0 44.20 17.92 2.0 4.7 Boznia-Herzegovina
Stations used:
HT.ALN HT.FNA HT.GRG HT.HORT HT.LIT HT.SOH HT.SRS HT.THE
HU.BUD HU.SOP II.BFO MN.PDG MN.TRI MN.VTS RO.ARR RO.BZS
RO.IAS RO.TESR RO.VOIR RO.VRI SL.BOJS SL.CADS SL.CEY
SL.CRES SL.GBAS SL.LJU SL.ROBS SL.SKDS SL.VISS
Filtering commands used:
hp c 0.02 n 3
lp c 0.05 n 3
Best Fitting Double Couple
Mo = 5.56e+22 dyne-cm
Mw = 4.43
Z = 16 km
Plane Strike Dip Rake
NP1 250 70 30
NP2 149 62 157
Principal Axes:
Axis Value Plunge Azimuth
T 5.56e+22 35 112
N 0.00e+00 54 281
P -5.56e+22 5 18
Moment Tensor: (dyne-cm)
Component Value
Mxx -4.49e+22
Mxy -2.89e+22
Mxz -1.44e+22
Myy 2.70e+22
Myz 2.28e+22
Mzz 1.79e+22
----------- P
--------------- ----
###-------------------------
####--------------------------
######----------------------------
#######-----------------------------
########------------------------------
##########--------------################
##########--------######################
############--############################
###########--#############################
########-----#############################
######--------################## #######
###------------################ T ######
#---------------############### ######
----------------######################
-----------------###################
------------------################
------------------############
--------------------########
---------------------#
--------------
Global CMT Convention Moment Tensor:
R T P
1.79e+22 -1.44e+22 -2.28e+22
-1.44e+22 -4.49e+22 2.89e+22
-2.28e+22 2.89e+22 2.70e+22
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.EU/20120727231222/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 = 250
DIP = 70
RAKE = 30
MW = 4.43
HS = 16.0
The waveform inversion is preferred.
Moment Tensor Comparison
The following compares this source inversion to others
| SLU |
USGSMT |
USGS/SLU Moment Tensor Solution
ENS 2012/07/27 23:12:22:0 44.20 17.92 2.0 4.7 Boznia-Herzegovina
Stations used:
HT.ALN HT.FNA HT.GRG HT.HORT HT.LIT HT.SOH HT.SRS HT.THE
HU.BUD HU.SOP II.BFO MN.PDG MN.TRI MN.VTS RO.ARR RO.BZS
RO.IAS RO.TESR RO.VOIR RO.VRI SL.BOJS SL.CADS SL.CEY
SL.CRES SL.GBAS SL.LJU SL.ROBS SL.SKDS SL.VISS
Filtering commands used:
hp c 0.02 n 3
lp c 0.05 n 3
Best Fitting Double Couple
Mo = 5.56e+22 dyne-cm
Mw = 4.43
Z = 16 km
Plane Strike Dip Rake
NP1 250 70 30
NP2 149 62 157
Principal Axes:
Axis Value Plunge Azimuth
T 5.56e+22 35 112
N 0.00e+00 54 281
P -5.56e+22 5 18
Moment Tensor: (dyne-cm)
Component Value
Mxx -4.49e+22
Mxy -2.89e+22
Mxz -1.44e+22
Myy 2.70e+22
Myz 2.28e+22
Mzz 1.79e+22
----------- P
--------------- ----
###-------------------------
####--------------------------
######----------------------------
#######-----------------------------
########------------------------------
##########--------------################
##########--------######################
############--############################
###########--#############################
########-----#############################
######--------################## #######
###------------################ T ######
#---------------############### ######
----------------######################
-----------------###################
------------------################
------------------############
--------------------########
---------------------#
--------------
Global CMT Convention Moment Tensor:
R T P
1.79e+22 -1.44e+22 -2.28e+22
-1.44e+22 -4.49e+22 2.89e+22
-2.28e+22 2.89e+22 2.70e+22
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.EU/20120727231222/index.html
|
USGS/SLU Regional Moment Solution
BOSNIA AND HERZEGOVINA
12/07/27 23:12:23.32
Epicenter: 44.182 17.903
MW 4.5
USGS/SLU REGIONAL MOMENT TENSOR
Depth 14 No. of sta: 19
Moment Tensor; Scale 10**15 Nm
Mrr=-0.23 Mtt=-3.93
Mpp= 4.15 Mrt=-2.39
Mrp=-0.87 Mtp= 3.88
Principal axes:
T Val= 6.19 Plg=16 Azm=114
N -0.07 65 242
P -6.12 18 19
Best Double Couple:Mo=6.2*10**15
NP1:Strike=157 Dip=66 Slip=-178
NP2: 66 88 -24
|
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 0.05 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 0.5 245 80 -10 4.10 0.4062
WVFGRD96 1.0 65 80 -10 4.13 0.4273
WVFGRD96 2.0 65 75 -10 4.20 0.4821
WVFGRD96 3.0 65 75 -15 4.24 0.5087
WVFGRD96 4.0 250 90 -5 4.28 0.5199
WVFGRD96 5.0 70 85 15 4.31 0.5235
WVFGRD96 6.0 70 80 15 4.33 0.5308
WVFGRD96 7.0 70 75 15 4.35 0.5432
WVFGRD96 8.0 70 80 25 4.37 0.5534
WVFGRD96 9.0 255 65 30 4.40 0.5681
WVFGRD96 10.0 255 65 30 4.41 0.5804
WVFGRD96 11.0 255 65 30 4.42 0.5893
WVFGRD96 12.0 255 65 30 4.42 0.5957
WVFGRD96 13.0 250 70 30 4.41 0.6010
WVFGRD96 14.0 250 70 30 4.42 0.6052
WVFGRD96 15.0 250 70 30 4.42 0.6084
WVFGRD96 16.0 250 70 30 4.43 0.6099
WVFGRD96 17.0 250 70 25 4.44 0.6098
WVFGRD96 18.0 250 70 25 4.45 0.6091
WVFGRD96 19.0 250 70 25 4.46 0.6077
WVFGRD96 20.0 250 70 25 4.46 0.6046
WVFGRD96 21.0 250 70 25 4.47 0.6019
WVFGRD96 22.0 250 70 25 4.48 0.5968
WVFGRD96 23.0 250 70 25 4.48 0.5907
WVFGRD96 24.0 250 70 20 4.50 0.5854
WVFGRD96 25.0 250 70 20 4.51 0.5785
WVFGRD96 26.0 250 70 20 4.51 0.5707
WVFGRD96 27.0 250 70 20 4.52 0.5633
WVFGRD96 28.0 245 75 20 4.51 0.5553
WVFGRD96 29.0 245 75 20 4.51 0.5474
The best solution is
WVFGRD96 16.0 250 70 30 4.43 0.6099
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 0.05 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=Sat Jul 28 12:00:35 CDT 2012
Last Changed 2012/07/27