The Holocene paleoearthquakes on the 1915 Avezzano earthquake faults (central Italy): implications for active tectonics in the central Apennines

Extensive paleoseismological research was conducted in the Fucino Plain (central Italy) in order to better understand the seismogenic characteristics of the fault responsible for the 1915 Avezzano earthquake (M-s = 7.0) and improve the general knowledge regarding active tectonics in the central Apennines. Evidence for Late Pleistocene-Holocene surface faulting events was obtained through the study of thirteen sites across four different fault branches. The paleoseismological analysis outlined the occurrence of ten surface faulting events in the past 33,000 years, seven of which occurred during the Holocene. Radiocarbon, thermoluminescence and archaeological dating permitted the definition of an event chronology and the estimation of a recurrence interval for surface faulting events ranging between 1400 and 2600 years. On the basis of the observed offsets it was possible to calculate vertical slip rates for the individual fault branches, ranging between 0.24 mm yr(-1) and 0.5 mm yr(-1) and an extension rate across the Fucino Plain ranging between 0.6 and 1 mm yr(-1). The chronology of surface faulting events appears linearly distributed in time, and the observed recurrence times are similar to those inferred by other paleoseismological studies along different active Apennine faults. The general consequence of the large time span between strong earthquakes is that even a 2000 year long historical record, such as the Italian earthquake catalogue, does not cover the entire seismic cycle of all the active Apennine faults. A comparison of the extension rate across the Fucino Plain with that across the entire central Apennines (as inferred from the sum of seismic moments of earthquakes which occurred in the interval 1000-1992) shows a seismicity 'deficit' in the period indicated. This confirms that a number of seismogenic faults were not active during the past 1000 years. (C) 1999 Elsevier Science B.V. All rights reserved.