Location

Location ANSS

Focal Mechanism

USGS/SLU Moment Tensor Solution ENS 2022/04/22 21:07:50:0 43.04 18.19 19.2 5.6 Bosnia-Herzegovina Stations used: AC.BCI AC.KBN AC.PHP BS.BLKB CR.ZAG HL.PENT HT.FNA1 HT.FNA5 HT.GRG HT.KPRO HT.LIT HT.NEST HT.THE HU.AMBH HU.BEHE HU.CSKK HU.EGYH HU.KOVH HU.MORH HU.MPLH HU.TIH MN.BLY MN.PDG MN.TIR MN.TRI OE.OBKA OE.SOKA RO.BAIL RO.BZS RO.DEV RO.GZR RO.HERR RO.MDVR RO.PUNG RO.SIRR SJ.BBLS SJ.FRGS SL.BOJS SL.CEY SL.CRES SL.DOBS SL.GBAS SL.GBRS SL.GOLS SL.GROS SL.JAVS SL.KNDS SL.KOGS SL.LJU SL.MOZS SL.PDKS SL.PERS SL.SKDS SL.VISS SL.VNDS SL.VOJS Filtering commands used: cut o DIST/3.3 -30 o DIST/3.3 +70 rtr taper w 0.1 hp c 0.02 n 3 lp c 0.07 n 3 Best Fitting Double Couple Mo = 3.16e+24 dyne-cm Mw = 5.60 Z = 24 km Plane Strike Dip Rake NP1 116 65 95 NP2 285 25 80 Principal Axes: Axis Value Plunge Azimuth T 3.16e+24 69 35 N 0.00e+00 4 294 P -3.16e+24 20 203 Moment Tensor: (dyne-cm) Component Value Mxx -2.11e+24 Mxy -7.97e+23 Mxz 1.80e+24 Myy -2.76e+23 Myz 9.99e+23 Mzz 2.39e+24 -------------- ---------------------- ---------#######------------ ----###################------- ---#########################------ --#############################----- ##################################---- #--################### ############--- ----################## T #############-- -------################ ##############-- --------################################-- -----------##############################- -------------############################- ---------------######################### -------------------##################### -----------------------############### ------------------------------------ ---------------------------------- ------- -------------------- ------ P ------------------- --- ---------------- -------------- Global CMT Convention Moment Tensor: R T P 2.39e+24 1.80e+24 -9.99e+23 1.80e+24 -2.11e+24 7.97e+23 -9.99e+23 7.97e+23 -2.76e+23 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20220422210750/index.html

Preferred Solution

      STK = 285
      DIP = 25
     RAKE = 80
       MW = 5.60
       HS = 24.0

The NDK file is 20220422210750.ndk The waveform inversion is preferred.

Moment Tensor Comparison

The following compares this source inversion to others

SLU	USGSW	OTHER
USGS/SLU Moment Tensor Solution ENS 2022/04/22 21:07:50:0 43.04 18.19 19.2 5.6 Bosnia-Herzegovina Stations used: AC.BCI AC.KBN AC.PHP BS.BLKB CR.ZAG HL.PENT HT.FNA1 HT.FNA5 HT.GRG HT.KPRO HT.LIT HT.NEST HT.THE HU.AMBH HU.BEHE HU.CSKK HU.EGYH HU.KOVH HU.MORH HU.MPLH HU.TIH MN.BLY MN.PDG MN.TIR MN.TRI OE.OBKA OE.SOKA RO.BAIL RO.BZS RO.DEV RO.GZR RO.HERR RO.MDVR RO.PUNG RO.SIRR SJ.BBLS SJ.FRGS SL.BOJS SL.CEY SL.CRES SL.DOBS SL.GBAS SL.GBRS SL.GOLS SL.GROS SL.JAVS SL.KNDS SL.KOGS SL.LJU SL.MOZS SL.PDKS SL.PERS SL.SKDS SL.VISS SL.VNDS SL.VOJS Filtering commands used: cut o DIST/3.3 -30 o DIST/3.3 +70 rtr taper w 0.1 hp c 0.02 n 3 lp c 0.07 n 3 Best Fitting Double Couple Mo = 3.16e+24 dyne-cm Mw = 5.60 Z = 24 km Plane Strike Dip Rake NP1 116 65 95 NP2 285 25 80 Principal Axes: Axis Value Plunge Azimuth T 3.16e+24 69 35 N 0.00e+00 4 294 P -3.16e+24 20 203 Moment Tensor: (dyne-cm) Component Value Mxx -2.11e+24 Mxy -7.97e+23 Mxz 1.80e+24 Myy -2.76e+23 Myz 9.99e+23 Mzz 2.39e+24 -------------- ---------------------- ---------#######------------ ----###################------- ---#########################------ --#############################----- ##################################---- #--################### ############--- ----################## T #############-- -------################ ##############-- --------################################-- -----------##############################- -------------############################- ---------------######################### -------------------##################### -----------------------############### ------------------------------------ ---------------------------------- ------- -------------------- ------ P ------------------- --- ---------------- -------------- Global CMT Convention Moment Tensor: R T P 2.39e+24 1.80e+24 -9.99e+23 1.80e+24 -2.11e+24 7.97e+23 -9.99e+23 7.97e+23 -2.76e+23 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20220422210750/index.html	W-phase Moment Tensor (Mww) Moment 4.649e+17 N-m Magnitude 5.71 Mww Depth 17.5 km Percent DC 69% Half Duration 1.86 s Catalog US Data Source US 1 Contributor US 1 Nodal Planes Plane Strike Dip Rake NP1 298° 18° 94° NP2 114° 73° 89° Principal Axes Axis Value Plunge Azimuth T 4.215e+17 N-m 62° 22° N 0.771e+17 N-m 1° 114° P -4.986e+17 N-m 27° 205°	EMSC-CSEM

Magnitudes

ML Magnitude

(a) ML computed using the IASPEI formula for Horizontal components; (b) ML residuals computed using a modified IASPEI formula that accounts for path specific attenuation; the values used for the trimmed mean are indicated. The ML relation used for each figure is given at the bottom of each plot.

(a) ML computed using the IASPEI formula for Vertical components (research); (b) ML residuals computed using a modified IASPEI formula that accounts for path specific attenuation; the values used for the trimmed mean are indicated. The ML relation used for each figure is given at the bottom of each plot.

Context

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.

Location of broadband stations used for waveform inversion

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 o DIST/3.3 -30 o DIST/3.3 +70
rtr
taper w 0.1
hp c 0.02 n 3 
lp c 0.07 n 3 

           DEPTH  STK   DIP  RAKE   MW    FIT
WVFGRD96    1.0   110    45   -90   5.20 0.3048
WVFGRD96    2.0   110    45   -90   5.29 0.3696
WVFGRD96    3.0   120    50   -90   5.36 0.3261
WVFGRD96    4.0    85    80   -25   5.29 0.2944
WVFGRD96    5.0    85    85   -30   5.31 0.2911
WVFGRD96    6.0   265    90    35   5.32 0.2948
WVFGRD96    7.0   175    20   -20   5.33 0.3214
WVFGRD96    8.0   155    15   -40   5.41 0.3476
WVFGRD96    9.0   105    80    85   5.42 0.3806
WVFGRD96   10.0   300    15   100   5.44 0.4171
WVFGRD96   11.0   110    70    85   5.46 0.4525
WVFGRD96   12.0   295    20    95   5.47 0.4871
WVFGRD96   13.0   290    20    90   5.48 0.5169
WVFGRD96   14.0   110    65    90   5.50 0.5435
WVFGRD96   15.0   290    25    90   5.51 0.5680
WVFGRD96   16.0   290    25    90   5.52 0.5887
WVFGRD96   17.0   115    65    95   5.53 0.6059
WVFGRD96   18.0   115    65    95   5.54 0.6202
WVFGRD96   19.0   115    65    95   5.55 0.6315
WVFGRD96   20.0   115    65    95   5.56 0.6406
WVFGRD96   21.0   115    65    95   5.58 0.6472
WVFGRD96   22.0   285    25    80   5.59 0.6512
WVFGRD96   23.0   285    25    80   5.59 0.6534
WVFGRD96   24.0   285    25    80   5.60 0.6537
WVFGRD96   25.0   285    25    80   5.61 0.6528
WVFGRD96   26.0   285    25    80   5.62 0.6503
WVFGRD96   27.0   285    25    80   5.62 0.6461
WVFGRD96   28.0   285    25    80   5.63 0.6407
WVFGRD96   29.0   280    30    70   5.64 0.6338

The best solution is

WVFGRD96   24.0   285    25    80   5.60 0.6537

The mechanism correspond to the best fit is

Figure 1. Waveform inversion focal mechanism

The best fit as a function of depth is given in the following figure:

Figure 2. Depth sensitivity for waveform mechanism

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 o DIST/3.3 -30 o DIST/3.3 +70
rtr
taper w 0.1
hp c 0.02 n 3 
lp c 0.07 n 3 

Figure 3. Waveform comparison for selected depth

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:

• 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)

 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

Acknowledgements

Thanks also to the many seismic network operators whose dedication make this effort possible: University of Nevada Reno, University of Alaska, University of Washington, Oregon State University, University of Utah, Montana Bureas of Mines, UC Berkely, Caltech, UC San Diego, Saint Louis University, University of Memphis, Lamont Doherty Earth Observatory, the Iris stations and the Transportable Array of EarthScope.

Velocity Model

The WUS.model 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: