The RTL Anomaly of Seismicity before the February 6, 2023 Earthquake in Turkey

Abstract—Based on the data from the regional Turkey earthquake catalog and the ANSS Comprehensive Earthquake Catalog for Turkey and a part of Iran, a posteriori analysis of RTL anomalies of seismicity before the damaging M_w 7.8 Pazarcik earthquake in Turkey of February 6, 2023 and, for comparison, before the M_w 7.1 earthquake of October 23, 2011 (Eastern Turkey), the M_w 7.3 earthquake of November 12, 2017 (Iran), and the М 6.7 earthquake of January 24, 2020 (the East Anatolian Fault), was made. Distinctly observable before the Pazarcik earthquake is an RTL anomaly with well-marked stages of a seismic quiescence and subsequent activation near the epicenter of the future earthquake. Spatially, the anomaly is one-and-a-half times smaller than the source of the Pazarcik earthquake, and one-and-a-half—two times smaller than RTL anomalies before other regional earthquakes with a magnitude above 7. By size, it corresponds to the anomaly before the M_w 6.7 earthquake that occurred on the same fault. As a hypothesis to explain why the size of the anomaly before the M_w 7.8 Pazarcik earthquake does not match the sizes of the anomalies characteristic of M7+ earthquakes, it was assumed that the detected RTL anomaly reflects the formation only of the first, relatively small segment of the source of the Pazarcik earthquake.