Relative stress evolution of the Straits of Messina area in the period 1950–1980 as determined from seismicity

Summary

Geodetic measurements recently completed in the Straits of Messina area have shown that both horizontal and vertical deformations of a few centimeters have taken place in the immediate surroundings of the fault system which originated the December 28, 1908M=7.0 eartquake in the last decade. This deformation can be ascribed to either aseismic slip or tectonic strain accumulation on a locked fault. Theb value relation to critical stress has been used to discriminate between the two alternatives. We used the data of Messina seismographic station in the period 1950–1979 comparing also with catalog data for the period 1910–1950. No clear trend in theb value is found and it is therefore concluded that the area did not undergo significant stress changes, implying an aseismic slip origin for the measured deformation. A modification of the Aki-Utsu maximum-likelihood method accounting for indeterminacy in the threshold magnitudeM ₀ is used in theb value estimate.