Palaeoseismologic and geomorphic investigations along the middle portion of the Ovindoli-Pezza Fault (Central Italy)

Abstract

his paper presents the results of a detailed investigation performed along the central part of the Ovindoli- Pezza Fault with the aim of improving our understanding of the seismic behaviour of this fault within Central Italy seismogenesis. Results of the trenching investigations we performed across the central part of the fault confirm and strengthen the results obtained at other sites located in the northern part. There is clear evidence that the two most recent surface faulting events occurred within the same interval of time at the different trench sites and thus, at least during these two events, the fault was activated for its entire length. The most recent surface faulting event occurred between 860 and 1300 A.D. Geomorphic and microtopographic investigations indicate that although the trace of the fault shows an important bend, the kinematics of the fault seem to be prevalently normal, consistent with the other seismogenic faults that accommodate the NE-SW extension in this part of the Apennines. The maximum horizontal movement derived using geomorphic methods along the central part of the Ovindoli-Pezza Fault did not exceed 30% of the vertical movement. Slip rate and average recurrence interval were obtained using data both from trenching and Late Pleistocene-Holocene geomorphology. Resulting slip rate ranges between 0.7 and 1.2 mm/year whereas the average recurrence time varies between 1000 and 3000 years.