Abstract

—Ground Penetrating Radar (GPR) surveys in the area between Sherashevo and Inkino villages provide insights into the structure of the Delta Fault and allow estimating the amount of vertical slip caused by the M = 7.5 Tsagan earthquake of 12 January 1862. The surveys with shielded AB-90 and AB 250-M antennas of an OKO-2 georadar along five profiles spaced at 25 m reveal normal slip from 2.6 to 4.5 m in different segments of the main seismogenic fault. The surface rupture caused by the 1862 event is traceable in interpreted radar images together with subsidiary faults; some possibly resulted from the 1959 Middle Baikal earthquake (M = 6.8). The GPR data are used to construct a 3D model of the area, which illustrates the evolution of the Delta Fault scarp since the Tsagan earthquake. Much of surface rupture during the Tsagan event is due to gravity sliding, judging by the amount of displacement estimated from GPR, structural, and field data of different years. Comprehensive understanding of the displacement pattern along the seismogenic fault requires further study extended to other segments of the fault zone.

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