Long-term earthquake triggering in the Southern and Northern Apennines

Abstract

We argue that the study of long-range interaction between seismic sources in the peri-Adriatic regions may significantly contribute to estimating seismic hazard in Italy. This hypothesis is supported by the reconstruction of the geodynamic and tectonic settings in the Central Mediterranean region, the space–time distribution of major past earthquakes, and the quantification of post-seismic relaxation. The most significant evidence of long-distance interaction is recognized for the Southern Apennines, whose major earthquakes have almost regularly followed within a few years the largest events in the Montenegro-Albania zone since 1850. Statistical analyses of the post-1850 earthquake catalogues give a probability of about 10% that a major event in the Southern Apennines is not preceded by the occurrence of a strong event in the Southern Dinarides–Albanides within 3–5 years. Conversely, the probability of false alarms is relevant (50% within 3 years, 33% within 5 years). Northward, the tectonic setting and some patterns of regularity seen in major events suggest that the seismic activation of the main transtensional decoupling shear zones in the Central Apennines should influence the probability of major earthquakes in the Northern Apennines.