Location

2011/05/24 02:55:29 39.0990 28.9570 5.0 0.00 Turkey

Arrival Times (from USGS)

Felt Map

Focal Mechanism

USGS/SLU Moment Tensor Solution ENS 2011/05/24 02:55:29:5 39.10 28.96 5.0 0.0 Turkey Stations used: GE.APE GE.ISP KO.ADVT KO.ANTB KO.ARMT KO.BALB KO.BCK KO.BGKT KO.BNN KO.BODT KO.BZK KO.CTKS KO.EDC KO.EDRB KO.ERIK KO.EZN KO.GELI KO.GEMT KO.GULT KO.HRTX KO.ISK KO.KCTX KO.KDZE KO.KLYT KO.KONT KO.KRBG KO.LAP KO.LOD KO.MDNY KO.MDUB KO.MERS KO.RKY KO.SPNC KO.SVRH KO.YER Filtering commands used: hp c 0.02 n 3 lp c 0.05 n 3 Best Fitting Double Couple Mo = 2.11e+22 dyne-cm Mw = 4.15 Z = 14 km Plane Strike Dip Rake NP1 218 71 137 NP2 325 50 25 Principal Axes: Axis Value Plunge Azimuth T 2.11e+22 43 174 N 0.00e+00 44 19 P -2.11e+22 13 276 Moment Tensor: (dyne-cm) Component Value Mxx 1.09e+22 Mxy 8.86e+20 Mxz -1.10e+22 Myy -1.97e+22 Myz 5.79e+21 Mzz 8.80e+21 ############## ###################### ----------###############--- ---------------########------- -------------------###------------ ---------------------#-------------- --------------------#####------------- -------------------#########------------ ------------------###########----------- - -------------##############----------- - P ------------################---------- - ----------###################--------- -------------####################--------- -----------######################------- ----------#######################------- --------########################------ -------########### ##########----- -----############ T ##########---- --############# ##########-- -#########################-- ###################### ############## Global CMT Convention Moment Tensor: R T P 8.80e+21 -1.10e+22 -5.79e+21 -1.10e+22 1.09e+22 -8.86e+20 -5.79e+21 -8.86e+20 -1.97e+22 Details of the solution is found at http://www.eas.slu.edu/Earthquake_Center/MECH.NA/20110524025529/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 = 325
      DIP = 50
     RAKE = 25
       MW = 4.15
       HS = 14.0

The waveform inversion is preferred.

Moment Tensor Comparison

The following compares this source inversion to others

SLU

USGS/SLU Moment Tensor Solution ENS 2011/05/24 02:55:29:5 39.10 28.96 5.0 0.0 Turkey Stations used: GE.APE GE.ISP KO.ADVT KO.ANTB KO.ARMT KO.BALB KO.BCK KO.BGKT KO.BNN KO.BODT KO.BZK KO.CTKS KO.EDC KO.EDRB KO.ERIK KO.EZN KO.GELI KO.GEMT KO.GULT KO.HRTX KO.ISK KO.KCTX KO.KDZE KO.KLYT KO.KONT KO.KRBG KO.LAP KO.LOD KO.MDNY KO.MDUB KO.MERS KO.RKY KO.SPNC KO.SVRH KO.YER Filtering commands used: hp c 0.02 n 3 lp c 0.05 n 3 Best Fitting Double Couple Mo = 2.11e+22 dyne-cm Mw = 4.15 Z = 14 km Plane Strike Dip Rake NP1 218 71 137 NP2 325 50 25 Principal Axes: Axis Value Plunge Azimuth T 2.11e+22 43 174 N 0.00e+00 44 19 P -2.11e+22 13 276 Moment Tensor: (dyne-cm) Component Value Mxx 1.09e+22 Mxy 8.86e+20 Mxz -1.10e+22 Myy -1.97e+22 Myz 5.79e+21 Mzz 8.80e+21 ############## ###################### ----------###############--- ---------------########------- -------------------###------------ ---------------------#-------------- --------------------#####------------- -------------------#########------------ ------------------###########----------- - -------------##############----------- - P ------------################---------- - ----------###################--------- -------------####################--------- -----------######################------- ----------#######################------- --------########################------ -------########### ##########----- -----############ T ##########---- --############# ##########-- -#########################-- ###################### ############## Global CMT Convention Moment Tensor: R T P 8.80e+21 -1.10e+22 -5.79e+21 -1.10e+22 1.09e+22 -8.86e+20 -5.79e+21 -8.86e+20 -1.97e+22 Details of the solution is found at http://www.eas.slu.edu/Earthquake_Center/MECH.NA/20110524025529/index.html

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:

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   275    40   -65   3.88 0.4934
WVFGRD96    1.0   270    40   -75   3.92 0.4973
WVFGRD96    2.0   280    40   -60   3.99 0.5450
WVFGRD96    3.0   285    35   -55   4.06 0.5280
WVFGRD96    4.0   295    30   -40   4.09 0.5068
WVFGRD96    5.0   300    30   -30   4.09 0.5140
WVFGRD96    6.0   305    30   -25   4.09 0.5286
WVFGRD96    7.0   310    35   -20   4.08 0.5414
WVFGRD96    8.0   305    30   -30   4.14 0.5670
WVFGRD96    9.0   305    30   -30   4.14 0.5753
WVFGRD96   10.0   305    30   -30   4.14 0.5800
WVFGRD96   11.0   310    35   -20   4.13 0.5830
WVFGRD96   12.0   325    45    20   4.14 0.5883
WVFGRD96   13.0   325    50    25   4.15 0.5924
WVFGRD96   14.0   325    50    25   4.15 0.5947
WVFGRD96   15.0   325    50    25   4.16 0.5936
WVFGRD96   16.0   325    50    25   4.16 0.5902
WVFGRD96   17.0   325    50    25   4.17 0.5847
WVFGRD96   18.0   320    55    25   4.17 0.5780
WVFGRD96   19.0   320    55    25   4.18 0.5709
WVFGRD96   20.0   320    55    25   4.18 0.5626
WVFGRD96   21.0   320    55    25   4.19 0.5513
WVFGRD96   22.0   320    55    25   4.19 0.5417
WVFGRD96   23.0   320    55    25   4.20 0.5315
WVFGRD96   24.0   320    55    25   4.20 0.5209
WVFGRD96   25.0   320    55    25   4.20 0.5101
WVFGRD96   26.0   320    55    25   4.21 0.4991
WVFGRD96   27.0   320    55    25   4.21 0.4879
WVFGRD96   28.0   320    60    30   4.22 0.4765
WVFGRD96   29.0   320    60    30   4.23 0.4655

The best solution is

WVFGRD96   14.0   325    50    25   4.15 0.5947

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

hp c 0.02 n 3
lp c 0.05 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)

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

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 May 24 03:02:23 CDT 2011

Last Changed 2011/05/24