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Russian Geology and Geophysics

2010 year, number 4

ACTIVITY RATING OF PLIOCENE–QUATERNARY FAULTS: A FORMALIZED APPROACH ( example of the Baikal Rift system )

O.V. Lunina
Institute of the Earth’s Crust, Siberian Branch of the Russian Academy of Sciences, 128 ul. Lermontova, Irkutsk, 664033, Russia
Keywords: Faults, activity rating, database, seismic hazard
Pages: 412-422

Abstract

It is suggested to estimate the Pliocene–Quaternary fault activity in a formalized way from synthesis of different data. The respective database consists of two main sections: general information and basic fault parameters and geomorphic, structural, paleoseismic, seismological, geophysical, geodetic, engineering-geological, hydrological, and meteorological data. The fault characteristics are scored according to their significance, and the cumulative score measures the fault activity. With this approach, the faults in the Barguzin and Tunka rift basins and in the northeastern flank of the Baikal Rift system have been divided into five activity classes (low, medium, relatively high, high, and very high activity) and mapped correspondingly. It has been recommended that the concept of a hazardous fault, as updated with regard to the activity rating, refer to faults of relatively high, high, and very high activity. Thus identified hazardous faults within the study area are quite few (4–8 %), though this percent may increase slightly as more input data become available. The underestimation cannot be dramatic because all known seismological and structural characteristics of faults essential for the activity rating have been already taken into account. The new approach may be useful in seismic risk assessment and in choice of sites for instrumental monitoring of seismicity.