Southern East Siberia Pliocene–Quaternary faults: Database, analysis and inference

This paper presents the first release of an Informational System (IS) devoted to the systematic collection of all available data relating to PlioceneeQuaternary faults in southern East Siberia, their critical analysis and their seismotectonic parameterization. The final goal of this project is to form a new base for improving the assessment of seismic hazard and other natural processes associated with crustal deformation. The presented IS has been exploited to create a relational database of active and conditionally active faults in southern East Siberia (between 100e114 E and 50e57 N) whose central sector is characterized by the highly seismic Baikal rift zone. The information within the database for each fault segment is organized as distinct but intercorrelated sections (tables, texts and pictures, etc.) and can be easily visualized as HTML pages in offline browsing. The preliminary version of the database distributed free on disk already highlights the general fault pattern showing that the Holocene and historical activity is quite uniform and dominated by NEeSW and nearly EeWtrending faults; the former with a prevailing dip-slip normal kinematics, while the latter structures are left-lateral strike-slip and oblique-slip (with different proportion of left-lateral and normal fault slip components). These faults are mainly concentrated along the borders of the rift basins and are the main sources of moderate-to-strong (M 5.5) earthquakes on the southern sectors of East Siberia in recent times. As a whole, based on analyzing the diverse fault kinematics and their variable spatial distribution with respect to the overall pattern of the tectonic structures formed and/or activated during the late PlioceneeQuaternary, we conclude they were generated under a regional stress field mainly characterized by a relatively uniform NWeSE tension, but strongly influenced by the irregular hard boundary of the old Siberian craton. The obtained inferences are in an agreement with the existing models of the development of the Baikal region