Study of active faults: Theoretical and applied implications

Abstract

Theoretical and applied implications of the study of active faults and their identification and parametrization are discussed. The term active fault is defined as a fault with displacements that occurred in the late Pleistocene and Holocene and are expected to resume in the future. The displaced young landforms, late Quaternary sediments, and man-made constructions are the main reference marks to recognize active faults and estimate their kinematics and intensity. Since the structural pattern and parameters of all active faults are referred to the same, geologically short time interval, they are important for the study of recent geodynamics and young tectogenesis on the global, regional, and local scales. The opportunities that are opened for such investigations are illustrated by verification of the real existence of the Okhotsk and Bering minor plates. With allowance for active faults, it is possible to make tectonic and geodynamic reconstructions of the past events more plausible. Natural hazards, primarily, earthquakes, are related to active faults. The geological and geomorphic assessment of the seismic potential of active fault zones is discussed with emphasis on the maximum possible magnitude of earthquakes (Mmax) estimated from the segmentation of the active zones, the length of particular segments (L), the empirical relationships Mmax/L for strong recent earthquakes, as well as the resumption periods of strong earthquakes and measurement of particular seismogenic offsets by trenching and other techniques, including archeoseismological methods. A question is posed about possible perennial variations in the stress-and-strain state of active zones, which are expressed on the scale of large seismoactive regions in oscillations of released seismic energy and should be taken into account by assessment of the seismic hazard.