Tectonophysical Zoning of Seismogenic Faults in Eastern Anatolia and February 6, 2023 Kahramanmaraş Earthquakes

Abstract

—The results of the tectonophysical reconstruction of stresses in the crust of Eastern Anatolia, obtained from the analysis of data on earthquake focal mechanisms, have shown that a significant restructuring of the stress state has occurred here in the last 20 years. It was largely confined to the southern and southwestern sectors of the region, covering hundreds of kilometers along the East Anatolian Fault. The data obtained from tectonophysical monitoring not only on the orientation of principal stresses, but also on their normalized values made it possible to calculate Coulomb stresses on faults. The results of fault zoning by intensity and sign of these stresses helped identify both hazardous sections close to the limit state and safe sections with negative Coulomb stress values. It has been established that in the region of the source of the first strong Pazarcık earthquake, which had a complex structure (three segments), there were extended sections with a critically high Coulomb stress level, separated by zones with low and even negative values of these stresses. The epicenter of this earthquake was located on the echelon fault within a section (first segment) with a high Coulomb stress level. The source of the second strong Elbistan earthquake was located on a fault with negative Coulomb stresses. The conducted analysis shows that this second Turkey earthquake may have been caused by stress changes that occurred in the crust of the region after the first strong earthquake. The research results show that Coulomb stresses in systems of closely located and differently oriented faults may be prone to sudden changes during the development of the earthquake on one of hazardous sections.