Features of the seismic process prior to a catastrophic earthquake in the area of the East Anatolian fault (February 6, 2023, MW = 7.8)

Abstract

Research subject. The seismic process in the area of the East Anatolian Fault (EAF), where two catastrophic earthquakes (doublet) occurred in February 2023.

Aim. Identification of specific features of the seismic process, which might indicate a connection (or a lack thereof) between the two earthquakes from the doublet, as well as the presence of any predictive signs before seismic events (medium- or short-term).

Materials and methods. An analysis of seismic activity graphs constructed by summing periods between earthquakes based on a local seismic catalog.

Results. Activity graphs were plotted for six regions at the epicenter of the first earthquake. Characteristic periods with a constant velocity of the seismic process and transition points were established. Local activations were detected in 2012 and 2022, which are confined to the epicenters of the doublet and are dominant for the EAF as a whole (for at least 300 km). All activations were timed to the same area slightly east of the epicenter of the February earthquake. It is shown that these activations do not correspond to the standard scheme of operation of a seismic center, i.e., they do not have an unambiguously determined main event and a characteristic aftershock process.

Conclusions. According to the distribution of earthquake epicenters, the local activation of 2012 was probably the initial stage in the development of the process, which was continued in 2022. The abrupt process of activity in 2022 ended 40 days prior to the earthquake doublet, and can be considered as a short-term predictive sign. The main characteristics of such a short-term anomaly in seismic activity are a reduction in the duration of each subsequent activation and a decrease in the time between them.