Coastal effects, tsunami and seiching associated with the kahramanmaraş turkey-syria twin earthquakes and aftershock sequence of february 2023

A strong M7.8 earthquake (02/06/2023; 01:17:36.1 UTC) followed by a second event (M7.5) on the same day (10:24:49 UTC) in Central Turkey caused extensive damage and fatalities (>> 50,000 in Turkey and Syria). Ground shaking exceeding 1.0 g in some locations (USGS, EMSC), structural damage, and multiple secondary effects were documented by Turkish and Greek reconnaissance teams in preliminary reports (e.g., (Lekkas, et al., 2023), reports to the EMSC). The M7+ earthquakes were widely felt in Turkey and in neighboring countries, such as Greece, the Balkan region, and Italy, as far as 1200 km and beyond. Flooding was also reported in few locations, including the bay of Alexandretta and in Salqin, Idlib, Syria. Sea level stations recorded a small tsunami, and tsunami runup was observed in Cyprus and Turkey. Through security cameras and personal cellphone footage, seismic seiches were recorded across Turkey and Cyprus. Some localities even reported multiple incidences of seiches over the course of the earthquake sequence in the same body of water. Observations of seiches are rare in the Eastern Mediterranean and are therefore especially valuable to document. Most importantly, the set of observations collected here is one-of-a-kind dataset (the most extensive dataset in Turkey and a unique dataset of seiche observations for Cyprus). Spatial analysis of seiche observations may also be valuable in documenting areas prone to liquefaction and vice versa, with particular use in the study of older or historical earthquakes. In this paper, we document the coastal effects of the Kahramanmaras Turkey earthquakes, followed by a first-order analysis. Satellite images were also processed to showcase the extent of flooding that followed the large twin earthquakes and lasted at least 3 days around the bay of Alexandretta. The source of flooding likely is a combination of subsidence, liquefaction and the tsunami that ensued. Tsunami amplitudes were small but clearly recorded in few stations; the tsunami’s genesis mechanism is in debate.