ALGORITHM FOR CONSTRAINING EARTHQUAKE SOURCE DOMAINS AND ESTIMATING THEIR POTENTIAL MAGNITUDES FROM GEOPHYSICAL DATA

Abstract

A two-stage algorithm for constraining earthquake source domains and estimating expected magnitudes of the potential earthquakes is suggested. Constraining of the EQ source domains in the crystalline crust of the study area is carried out by means of geophysical proxies derived from comparison of physical and mechanical properties of rocks in the hypocenters of past earthquakes and in the nodes of 3D grid covering appropriate models. At the second stage forecasting of the expected EQ magnitudes in the constrained source domains is fulfilled using artificial neural network taught by correspondence of the shear modulus determined in the hypocenters of past earthquakes and EQ magnitudes. Application of this algorithm to the Altai-Sayan seismically active area enabled to delineate earthquake source domains at different depths. Two of them were previously guessed from the surface seismicity data and interpreted in terms of the fault tectonics, whereas others have been constrained for the first time. The results of research indirectly support the hypothesis that rheological weakness of rocks is likely to be responsible for common physical and mechanical conditions controlling the occurrence of the earthquakes and evolution of the faults. Another important inference is that neither the statistical information on past seismicity alone nor speculations on fault tectonics are sufficient to constrain the ESDs in the Earth’s crust.