GEOPHYSICAL RESEARCH, 2018, vol. 19, no. 2, pp. 34-56. https://doi.org/10.21455/gr2018.2-2

UDC 550.343.6

Abstract  References   Full text (in Russian)  Full text (in English)

ESTIMATING AFTERSHOCK AREA BASED ON THE MAINSHOCK INFORMATION 

S.V. Baranov(1), P.N. Shebalin(2)

(1) Kola Branch of Federal Research Center Unified Geophysical Survey, RAS, Apatity, Russia

(2) Institute of Earthquake Prediction Theory and Mathematical Geophysics, RAS, Moscow, Russia

Abstract. The paper considers the task of quick estimating an area where aftershocks are expected after a strong earthquake using information about its mainshock. The suggested approach is based on the hypotheses by Y. Kagan that geometrical parameters of earthquake focal zones are self-similar. This hypothesis allows one to extend scaling relation connecting an earthquake magnitude and its fault size to the aftershock area size. The research data are ANSS Comprehensive Catalog (ComCat) provided by USGS and GCMT catalog that contains seismic moment tensors and fault plane solutions of earthquakes. We used data for 1975–2016 covering the whole Earth. It is shown that scaling relation Rµ100.5Mm (Mm is a mainshock magnitude, R is a distance from the mainshock to the most remote aftershock) is satisfied independently on time after the mainshock and the type of its focal mechanism. This relation allows modeling an aftershock area by a circle centered at the mainshock epicenter and radius that depends on the mainshock magnitude. The radiuses of circles, where aftershocks with magnitudes exceeding given values are expected with probabilities of 95 and 99%, are estimated for different time intervals after the mainshock and types of its focal mechanism. It is also proposed the way to evaluate the aftershock activity area, if the mainshock fault plane is known. In this case, the shape reminds a “stadium” being an area of the points equally-spaced from the line segment. The results obtained can be used in practice for estimating an area, where strong repeated shocks are expected after a strong earthquake.

Keywords: mainshock, aftershocks, scaling relation, fault plane solution, aftershock area.

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