Seismotectonic Position of the Source of the July 13, 2023, Earthquake in the Eastern Laptev Sea Shelf from Surface Wave Data

In this study, we consider in detail the July 13, 2023, earthquake that occurred on the shelf of the eastern Laptev Sea (Belkov–Svyatoi Nos rift). On the one hand, our interest in this event is due to the location of its epicenter, to the east of which there is a sharp decrease in seismic activity. Conversely, detailed common depth point (CDP) data on the structure of the upper crust are available for its epicentral zone, making it possible to analyze the seismotectonic position of the earthquake source. Focal parameters in the instantaneous point source approximation are calculated from surface waves recorded at teleseismic distances. As a result, we have obtained a scalar seismic moment (M₀ = 9.8 × 10¹⁶ N m), corresponding moment magnitude (M_w = 5.3), source depth (h = 8 km), and focal mechanism (a normal fault along a gently dipping nodal plane with a NW–SE strike). Our results are compared with data from seismological agencies. It has been shown that differences between them are most likely caused by various initial data, including their different frequency ranges. Our estimates agree better with the available geological and geophysical information on the tectonics of the study area. Taking into account the data on strike, dip, and penetration depth of faults and our source parameter values, we have concluded that the July 13, 2023, earthquake could have been associated with a major listric normal fault on the western slope of the Belkov–Svyatoi Nos rift.