Geotectonics

Volume 28, Number 3, December 1994
Russian Edition May -June 1994


Relict seismicity in the Alpine belt of Eurasia: Mode of occurrence

V. E. Khain

Institute of the Lithosphere, Russian Academy of Sciences, Moscow

L. I. Lobkovskiy

Institute of Oceanology, Russian Academy of Sciences, Moscow


Abstract

Specific features of the distribution of mantle earthquake foci in the Alpine-Himalaya belt have been analyzed and interpreted using the concepts of two-layer plate tectonic and intracontinental (C type) subduction. The discontinuous spatial distribution of seismic events and their confinement to transverse or diagonal fault zones depends on two basic factors. First, dissipative heating of the subcrustal parts of the plates, during subduction creates aseismic conditions and is responsible for the lack of a continuous belt of mantle seismicity. Secondly, water and other fluids simultaneously penetrate the zones of transcrustal faults from above and permeate plastic material of the subcrustal lithosphere so that intrapore pressure offsets the lithostatic pressure. As a result, the mantle rock acquires brittle properties near the zones of higher crustal permeability, i.e., near fracture zones.

Figures 4, Tables 0, References 35, Pages 192- 198
Received March 4, 1993

© Copyright 1995 by the American Geophysical Union.
CCC code: 0016-8521/95/2803-0002$18.00/1


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