Problems of Engineering Seismology: article

Аnnotation: We study in detail the January 20, 2013 Ulakhan-Chistay earthquake (MW = 5.6) which occurred at the north-east of Yakutia in the Chersky seismotectonic zone. This seismic event is of interest due to its connection with the Ulakhan fault, which is the largest rupture at the north-east of Russia and is accepted to be a boundary between the North-America, Eurasia, and Okhotsk lithospheric plates. Source parameters of the study earthquake were calculated from amplitude spectra of surface waves, registered at teleseismic distances. Firstly, the source was modeled in an instant point source approximation. As a result, we obtained a scalar seismic moment (M0 = 2.7·1017 N·m), corresponding moment magnitude (MW = 5.6), source depth (h = 18 km), and focal mechanism representing itself a left-lateral strike-slip with a thrust fault component. Then, we considered the source in a plane fault approximation. Our calculations of integral source parameters, characterizing fault geometry and time development, along with independent geological data allowed us to identify the fault plane (strike 131°, dip 53°, slip 25°). For this plane, the integral source duration is 0–2 s, and the lengths of the major and minor axes of the source ellipse are 15–20 and 0–10 km, respectively. It is worth noting that for earthquakes in Yakutia the estimates of the fault sizes, based directly on seismic wave records, have been obtained for the first time.