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Finite Fault Model of Mw 7.2 Eastern Turkey Earthquake,Oct 23, 2011

DATA Process and Inversion

It was used GSN broadband waveforms downloaded from the NEIC waveform server. It was analyzed 21 teleseismic broadband P waveforms, 6 broadband SH waveforms, and 27 long period surface waves selected based upon data quality and azimuthal distribution. Waveforms are first converted to displacement by removing the instrument response and then used to constrain the slip history based on a finite fault inverse algorithm (Ji et al., 2002). It was used the USGS hypocenter (Lon.=38.62 deg.; Lat.=43.48 deg.). The fault planes are defined using the rapid W-Phase moment tensor solution of the NEIC.

 

Result

After comparing the waveform fits based on two planes, it was found that both nodal planes fit the waveforms reasonaly well (NP1 strike=106.87 deg., dip=47.32 deg.; NP1 strike=239.26 deg., dip=53.83 deg.). The seismic moment release based upon these planes is 7.28e+26 dyne.cm (Mw7.17), and 8.24e+26 dyne.cm (Mw7.20) respectively, using a 1D crustal model interpolated from CRUST2.0 (Bassin et al., 2000).

 

Plane 1

Cross-section of slip distribution


Figure 1. Cross-section of slip distribution. The strike direction of the fault plane is indicated by the black arrow and the hypocenter location is denoted by the red star. The slip amplitude are showed in color and motion direction of the hanging wall relative to the footwall is indicated by black arrows. Contours show the rupture initiation time in seconds.

 

Moment Rate Function


Figure 2. Source time function, describing the rate of moment release with time after earthquake origin.
 

Comparison of data and synthetic seismograms


Figure 3. Comparison of teleseismic body waves. The data are shown in black and the synthetic seismograms are plotted in red. Both data and synthetic seismograms are aligned on the P or SH arrivals. The number at the end of each trace is the peak amplitude of the observation in micro-meters. The number above the beginning of each trace is the source azimuth and below is the epicentral distance. Shading describes relative weighting of the waveforms.

Figure 4.1. Comparison of long period surface waves. The data are shown in black and the synthetic seismograms are plotted in red. Both data and synthetic seismograms are aligned on the P or SH arrivals. The number at the end of each trace is the peak amplitude of the observation in micro-meter. The number above the beginning of each trace is the source azimuth and below is the epicentral distance. Shading describes relative weighting of the waveforms.
Figure 4.2. Comparison of long period surface waves. The data are shown in black and the synthetic seismograms are plotted in red. Both data and synthetic seismograms are aligned on the P or SH arrivals. The number at the end of each trace is the peak amplitude of the observation in micro-meter. The number above the beginning of each trace is the source azimuth and below is the epicentral distance. Shading describes relative weighting of the waveforms.
 

Plane 2

Cross-section of slip distribution


Figure 1. Cross-section of slip distribution. The strike direction of the fault plane is indicated by the black arrow and the hypocenter location is denoted by the red star. The slip amplitude are showed in color and motion direction of the hanging wall relative to the footwall is indicated by black arrows. Contours show the rupture initiation time in seconds.

 

Moment Rate Function


Figure 2. Source time function, describing the rate of moment release with time after earthquake origin.
 

Comparison of data and synthetic seismograms

Figure 3. Comparison of teleseismic body waves. The data are shown in black and the synthetic seismograms are plotted in red. Both data and synthetic seismograms are aligned on the P or SH arrivals. The number at the end of each trace is the peak amplitude of the observation in micro-meters. The number above the beginning of each trace is the source azimuth and below is the epicentral distance. Shading describes relative weighting of the waveforms.

Figure 4.1. Comparison of long period surface waves. The data are shown in black and the synthetic seismograms are plotted in red. Both data and synthetic seismograms are aligned on the P or SH arrivals. The number at the end of each trace is the peak amplitude of the observation in micro-meter. The number above the beginning of each trace is the source azimuth and below is the epicentral distance. Shading describes relative weighting of the waveforms.

Figure 4.2. Comparison of long period surface waves. The data are shown in black and the synthetic seismograms are plotted in red. Both data and synthetic seismograms are aligned on the P or SH arrivals. The number at the end of each trace is the peak amplitude of the observation in micro-meter. The number above the beginning of each trace is the source azimuth and below is the epicentral distance. Shading describes relative weighting of the waveforms.
 

Gavin's Comments:

Late slip in each model seems fairly unresoved, though it contributes to the total moment. The main slip patch, just to the west of the hypocenter in both models, is quite compact and simple, approximately 20 km along strike. In the second (north-dipping) model, slip may reach close to the surface. The potential for location bias in the NEIC teleseismic hypocenter solution means these models may shift ~10 km further north-northwest. Aftershock data from Turkey seem to favor a NE-SW distribution, more closely aligning with plane 2.

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