Stress accumulation on the Karlıova (Bingöl) Triple Junction after two big earthquakes (Pazarcık-Ekinözü) in Turkey in 2023

Abstract

Active fault zones primarily influence earthquakes in the Karl & imath;ova (Bing & ouml;l) region. The mentioned region is in Turkey's first and second seismic hazard zones; however, it also includes certain areas in the third and fourth seismic hazard zones. In this study, we investigated the earthquake activities using data collected from various global navigation satellite system (GNSS) surveys of continuously operating reference stations in Turkey (CORS-TR). We also analysed the Coulomb stress change caused by the 15 local earthquakes surrounding the Karl & imath;ova Triple Junction. Additionally, we investigated the relationship between Coulomb stress change and horizontal displacements from GNSS survey results, focusing on horizontal displacement vectors. Besides, gravity data were used to infer the fault geometries and shallow crustal structures. The largest horizontal movement was observed at the BIN1 station, the intersection point of the North Anatolian Fault Zone (NAFZ) and the East Anatolian Fault Zone (EAFZ). At the CORS-TR point on the Karl & imath;ova segment of the EAFZ, the horizontal displacement was calculated to be approximately 10.1 cm in the north-eastern direction. The observations of Coulomb stress change reveal that positive stress variations were observed in the NW-SE and SW-NE directions along the main fault line at a depth of approximately 30 km, in accordance with the tilt transformation of gravity anomalies.