Investigation of Earthquake Sequence and Stress Transfer in the Eastern Anatolia Fault Zone by Coulomb Stress Analysis

Abstract

A devastating earthquake with a magnitude of (M-w = 7.7) occurred on February 06, 2023, in the Pazarcik segment of the Eastern Anatolian Fault Zone, which has not shown major earthquake activity for a long time. On the same day, another earthquake with a magnitude of (M-w = 7.6) occurred in Ekinozu-Elbistan (Kahramanmaras) in the northwest. Three more earthquakes with magnitudes of M-w = 6.6, M-w = 5.9, and ML = 5.7 occurred on the same day, and significant damage, loss of life, and property occurred in 11 provinces and districts. A sixth earthquake occurred with M-w = 6.4 magnitude in Defne-Hatay on February 20, 2023. In addition, more than 32,000 aftershocks were recorded while this study was in progress. The interconnection of these earthquakes was investigated by Coulomb stress analysis. It showed compatibility with the distribution of both these six earthquakes and small aftershocks, in which earthquakes transfer stress to each other during their formation phases. By calculating Coulomb stress changes, mainshock ruptures have played an important role in transferring stresses between Elazig and Malatya in the northeast, Kahramanmaras-Goksun in the west, and Hatay and Syria in the south. Also, our calculations showed that shallow depths in and around source zones received positive stress changes (similar to 1.0 bar) due to the focal depths of mainshocks with their aftershocks. Finally, it has been better understood with these earthquakes that the stress transfer time of high-energy earthquakes can be shortened considerably.