A time- and magnitude-predictable model for generation of shallow earthquakes in the Aegean area

Abstract

Repeat times of strong shallow mainshocks have been determined by the use of instrumental and historical data for 68 seismogenic sources in the Aegean and surrounding area (34°N–43°N, 18°E–30°E). For 49 of these sources at least two interevent times (three mainshocks) are available for each source. By using the repeat times for these 49 sources the following relation has been determined:

$$\log T_t = 0.36M_{\min } + 0.35M_p + a$$

whereT _t is the repeat time, measured in years,M _p the surface wave magnitude of the preceding mainshock,M _min the magnitude of the smallest earthquake considered and “a” parameter which varies from source to source. A multilinear correlation coefficient equal to 0.89 was determined for this relation.

By using the same repeat times for the 49 seismogenic sources, the following relation has been determined between the magnitude,M _f , of the following mainshock andM _min andM _p .

$$M_f = 0.95M_{\min } - 0.49M_p + m$$

wherem is a constant which varies from source to source. A multilinear correlation coefficient equal to 0.80 was found for this relation.

The model expressed by these two relations is represented by a scheme of a time variation of stress under constant tectonic loading. In this scheme, the maximum stress values during the different seismic cycles fluctuate around a value, τ₁, in a relatively narrow stress interval, expressing the high correlation coefficient of the relation between LogT andM _p . On the contrary, the minimum stress values fluctuate around a value, τ₂, in a much broader stress interval. However, each of these minimum stress values becomes lower or higher than τ₂ if the previous one is higher or lower than τ₂, respectively, expressing the negative correlation betweenM _f andM _p .