2011/04/28 23:30:45 44.814 17.322 10.0 4.30 Boznia and Herzegovina
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution ENS 2011/04/28 23:30:45:3 44.81 17.32 10.0 4.3 Boznia and Herzegovina Stations used: CH.FUORN CH.SENIN CZ.KRUC CZ.PVCC GE.PSZ GE.STU GR.ASSE GR.BRG GR.CLL GR.CLZ GR.FUR GR.GRA1 GR.GRA2 GR.GRB2 GR.GRB4 GR.MOX GR.TNS GR.WET HU.PKSM HU.SOP II.BFO IU.GRFO MN.PDG MN.TIR MN.TRI MN.TUE OE.ABTA OE.ARSA OE.CONA OE.CSNA OE.DAVA OE.FETA OE.KBA OE.MOA OE.MYKA OE.OBKA OE.RETA OE.SOKA RO.BUR31 RO.BZS RO.DRGR RO.LOT RO.VOIR RO.VRI SL.CRES SL.LJU SL.PERS SL.VISS Filtering commands used: hp c 0.02 n 3 lp c 0.05 n 3 Best Fitting Double Couple Mo = 3.80e+22 dyne-cm Mw = 4.32 Z = 16 km Plane Strike Dip Rake NP1 136 60 145 NP2 245 60 35 Principal Axes: Axis Value Plunge Azimuth T 3.80e+22 45 100 N 0.00e+00 45 281 P -3.80e+22 0 190 Moment Tensor: (dyne-cm) Component Value Mxx -3.62e+22 Mxy -1.01e+22 Mxz -3.30e+21 Myy 1.73e+22 Myz 1.87e+22 Mzz 1.89e+22 -------------- ---------------------- ---------------------------- ------------------------------ ###------------------------------- ####-----------------------####----- #####--------------################### #######---------######################## ########-----########################### ##########-############################### #########--############################### #######-----################### ######## #####--------################## T ######## ###-----------################ ####### ##--------------######################## -----------------##################### ------------------################## --------------------############## -----------------------####### ---------------------------- ------ ------------- -- P --------- Global CMT Convention Moment Tensor: R T P 1.89e+22 -3.30e+21 -1.87e+22 -3.30e+21 -3.62e+22 1.01e+22 -1.87e+22 1.01e+22 1.73e+22 Details of the solution is found at http://www.eas.slu.edu/Earthquake_Center/MECH.NA/20110428233045/index.html |
STK = 245 DIP = 60 RAKE = 35 MW = 4.32 HS = 16.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution ENS 2011/04/28 23:30:45:3 44.81 17.32 10.0 4.3 Boznia and Herzegovina Stations used: CH.FUORN CH.SENIN CZ.KRUC CZ.PVCC GE.PSZ GE.STU GR.ASSE GR.BRG GR.CLL GR.CLZ GR.FUR GR.GRA1 GR.GRA2 GR.GRB2 GR.GRB4 GR.MOX GR.TNS GR.WET HU.PKSM HU.SOP II.BFO IU.GRFO MN.PDG MN.TIR MN.TRI MN.TUE OE.ABTA OE.ARSA OE.CONA OE.CSNA OE.DAVA OE.FETA OE.KBA OE.MOA OE.MYKA OE.OBKA OE.RETA OE.SOKA RO.BUR31 RO.BZS RO.DRGR RO.LOT RO.VOIR RO.VRI SL.CRES SL.LJU SL.PERS SL.VISS Filtering commands used: hp c 0.02 n 3 lp c 0.05 n 3 Best Fitting Double Couple Mo = 3.80e+22 dyne-cm Mw = 4.32 Z = 16 km Plane Strike Dip Rake NP1 136 60 145 NP2 245 60 35 Principal Axes: Axis Value Plunge Azimuth T 3.80e+22 45 100 N 0.00e+00 45 281 P -3.80e+22 0 190 Moment Tensor: (dyne-cm) Component Value Mxx -3.62e+22 Mxy -1.01e+22 Mxz -3.30e+21 Myy 1.73e+22 Myz 1.87e+22 Mzz 1.89e+22 -------------- ---------------------- ---------------------------- ------------------------------ ###------------------------------- ####-----------------------####----- #####--------------################### #######---------######################## ########-----########################### ##########-############################### #########--############################### #######-----################### ######## #####--------################## T ######## ###-----------################ ####### ##--------------######################## -----------------##################### ------------------################## --------------------############## -----------------------####### ---------------------------- ------ ------------- -- P --------- Global CMT Convention Moment Tensor: R T P 1.89e+22 -3.30e+21 -1.87e+22 -3.30e+21 -3.62e+22 1.01e+22 -1.87e+22 1.01e+22 1.73e+22 Details of the solution is found at http://www.eas.slu.edu/Earthquake_Center/MECH.NA/20110428233045/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.
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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 3The results of this grid search from 0.5 to 19 km depth are as follow:
DEPTH STK DIP RAKE MW FIT WVFGRD96 0.5 240 80 -25 4.04 0.4192 WVFGRD96 1.0 240 75 -20 4.06 0.4361 WVFGRD96 2.0 235 75 -35 4.14 0.4899 WVFGRD96 3.0 235 70 -30 4.16 0.4996 WVFGRD96 4.0 240 80 -30 4.18 0.4968 WVFGRD96 5.0 60 90 30 4.19 0.4949 WVFGRD96 6.0 65 65 15 4.22 0.5044 WVFGRD96 7.0 65 60 15 4.24 0.5178 WVFGRD96 8.0 70 55 20 4.29 0.5189 WVFGRD96 9.0 70 50 20 4.31 0.5265 WVFGRD96 10.0 70 50 20 4.31 0.5321 WVFGRD96 11.0 70 50 20 4.32 0.5351 WVFGRD96 12.0 70 50 25 4.33 0.5370 WVFGRD96 13.0 70 50 25 4.33 0.5372 WVFGRD96 14.0 245 60 35 4.31 0.5392 WVFGRD96 15.0 245 60 35 4.32 0.5417 WVFGRD96 16.0 245 60 35 4.32 0.5419 WVFGRD96 17.0 245 60 35 4.33 0.5409 WVFGRD96 18.0 245 60 35 4.33 0.5390 WVFGRD96 19.0 245 60 35 4.34 0.5360 WVFGRD96 20.0 245 60 30 4.35 0.5322 WVFGRD96 21.0 245 60 30 4.36 0.5264 WVFGRD96 22.0 245 60 30 4.36 0.5209 WVFGRD96 23.0 245 60 30 4.37 0.5146 WVFGRD96 24.0 245 60 30 4.37 0.5077 WVFGRD96 25.0 245 60 30 4.38 0.5002 WVFGRD96 26.0 245 65 25 4.39 0.4928 WVFGRD96 27.0 240 70 25 4.38 0.4855 WVFGRD96 28.0 240 70 25 4.39 0.4779 WVFGRD96 29.0 240 75 25 4.39 0.4699 WVFGRD96 30.0 240 75 25 4.40 0.4621 WVFGRD96 31.0 240 75 25 4.41 0.4539 WVFGRD96 32.0 55 70 -20 4.43 0.4506 WVFGRD96 33.0 55 70 -20 4.43 0.4448 WVFGRD96 34.0 65 55 20 4.46 0.4382 WVFGRD96 35.0 65 55 20 4.47 0.4347 WVFGRD96 36.0 65 55 20 4.48 0.4317 WVFGRD96 37.0 65 55 20 4.48 0.4294 WVFGRD96 38.0 65 55 20 4.49 0.4273 WVFGRD96 39.0 65 55 20 4.50 0.4253
The best solution is
WVFGRD96 16.0 245 60 35 4.32 0.5419
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 0.05 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=Thu Apr 28 21:08:01 MDT 2011