Палеосейсмогенные смещения в районе мыса Рытого на северо-западном побережье озера Байкал

Abstract

In connection with a series of sensible earthquakes in the Baikal-Mongolian region at the end of 2020 – beginning of 2021, the population of the area has increased interest in the zones of possible earthquake sources and their seismic potential. In this regard, we carried out a detailed mapping of paleoseismogenic deformations within one of the most mysterious places on Lake Baikal – Cape Rytyi and its vicinity crossed by the zone of the Kocherikovsky active fault. Along the ruptures in the rear part of the Rita river delta, based on displacement measurements of the original surfaces on the hypsometric profiles, the vertical displacements are reconstructed and compared with ground penetrating radar data. It has been established that the deformations in the studied area are associated with at least two paleoearthquakes. The maximum movement at the first one was 7,9 m, at the second one – 5,0 m. The magnitude estimates calculated from the known equations using these displacements were: <math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>M</mi><mi>W</mi></msub></math> of the earlier event 7,3, <math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>M</mi><mi>S</mi></msub></math> = 7,4; <math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>M</mi><mi>W</mi></msub></math> of the later event is 7,1, <math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>M</mi><mi>S</mi></msub></math> = 7,3. It is noted that the preservation of seismogenic scarps, their dip angles and the degree of burial strongly depend on the initial landscape and can differ even within a few hundred meters for a single rupture. This fact must be taken into account when conducting paleoearthquake studies and determining the rupture parameters.