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Russian Geology and Geophysics

2002 year, number 5

THE 25.02.1999 SOUTH BAIKAL EARTHQUAKE: SEISMOTECTONICS AND REGIONAL GEODYNAMICS

V. V. Ruzhich, R. M. Semenov, A. M. Alakshin, B. I. Mel'nikova, A. V. Chpizubov, S. G. Arzhannikov, O. P. Smekalin, I. A. Emel'yanova, M .G. Dem'yanovich, and N. A. Radziminovich
Keywords: keywords_eng||Epicentre, earthquake focus, aftershock, fault node, focal mechanism, active fault, earthquake energy, intensity
Pages: 470-483

Abstract

The South Baikal earthquake of 25 February, 1999 had the main shock in the south-western part of Lake Baikal with the normal-slip focus at the intersection of the Obruchev (Primorsky) and Angara faults. This was the strongest shock (MPSP = 6.0) in the southern Baikal region over the last 40 years after the MLH = 6.8 Central Baikal earthquake of 1959. The intensity attained 7-8 in the epicentre, 6-7 in villages 15 to 30 km away on the north-western and south-eastern sides of Baikal, and 4-6 in neighbouring cities of Irkutsk, Angarsk, and Ulan-Ude. The main shock was followed by a long series of aftershocks with different focal mechanisms. This event occurred in a region for which pending seismic risk in the nearest 15 years was predicted in 1994.