Bayesian modeling of co-seismic slip using GNSS data: 2002 Çay earthquake

In southwestern Turkey, in the Afyon-Sultandağı region, a mainshock of magnitude Mw 6.5 occurred at 07:11:28 (GMT) and was followed approximately two hours later at 09:26:49 (GMT) by an aftershock of magnitude Mw 5.8. The mainshock took place south of Eber Lake, causing surface discontinuities and significant surface deformation. Numerous researchers have studied the earthquake's source parameters using traditional teleseismic and geodetic data. However, to better visualize the co-seismic deformation and more accurately determine the geometry and slip distribution of the seismogenic fault, a Bayesian approach was adopted in this study. The Bayesian approach creates a posterior probability density function (PDF) that encompasses all possible values of model parameters by incorporating observations, prior physical knowledge of the source model, and the distribution of differences between forward model predictions and observations. In this study, geodetic datasets were utilized for both the rectangular source model and finite fault modeling. The results confirm that the 2002 Çay Earthquake predominantly involved a normal faulting mechanism with a significant left-lateral strike-slip component. The fault geometry, characterized by a strike angle of 277°, a dip angle of 43°, and a rake angle of -56°, aligns well with the regional tectonic framework. The uniform slip model, validated by the Bayesian method, effectively captured surface deformation patterns and achieved a variance reduction of 92%. This finding highlights the power of Bayesian methods in accurately modeling fault dynamics, particularly in regions with limited seismic data.