ANALISI ARCHEOSISMOLOGICHE NEL SANTUARIO DI ERCOLE DI CAMPOCHIARO (MATESE). EVIDENZE DI UN TERREMOTO DISTRUTTIVO SCONOSCIUTO ED IMPLICAZIONI SISMOTETTONICHE

Abstract

Archaeoseismological analyses in the Hercules’s sanctuary of Campochiaro (Matese, central-southern Apennine, Italy). Evidence of an
unknown disruptive earthquake and seismotectonic implication. Starting from the 6th cent. BC, a vast region of central-southern Italy
(Samnium) was inhabited and dominated by the daring nation of Samnites. Between the 4th and 3rd cent. BC Samnites and Romans
disputed for the hegemony of central Italy, but in 290 BC the former was finally subdued by the latter. Samnites raised many important
sanctuaries in their land, also after the Roman conquest, which remained in use until the decadence of the Empire. The sanctuary of
Hercules near Campochiaro is one of these; it was built in the 4th cent. BC, being frequented until the 4th-5th cent. AD (Fig. 10). It is
located close to the Campochiaro fault, a roughly E-W strand of the N-Matese massif structure, which borders and controls the formerlacustrine Bojano basin (Figg. 1, 7-8). Archaeoseismological analyses performed within the sanctuary area, supported by paleoseismological trenching (Figg. 11-12), geomorphological and geological surveys, allowed the identification of surface faulting of the archeological relics. Buildings of the primitive phase have been displaced by a first event in the middle of the 3rd cent. BC (Figg. 9, 13-15), whereas the following structures (built up over the faulted ruins of the former) show a subsequent offset, which we relate to the cumulated motion of the M=6.5~7 earthquakes of 1456 and 1805 (although we do not exclude other unknown High Middle Age events or the 346 AD earthquake). While the 3rd cent. BC earthquake is unknown to the Italian historical catalogues, the 1456 and 1805 events are well characterized in terms of intensity datapoint distribution (Figg. 5-6), and could both be related to the N-Matese massif seismogenetic structure (faults of Mt. Patalecchia-Bojano-Campochiaro; Fig. 1). According to our interpretation, the seismogenetic behaviour of the NMatese massif structure is rather complex, and does not follow the recurrence interval showed by other Apenninic faults (2000±500 yr; see Galadini and Galli, 2000); on the other hand, its slip-rate (0.9 mm/yr) would be one of the highest in Italy. These results sugges that the use of a Poisson approach (which requires stationarity in earthquake occurrence) in seismic hazard evaluation studies could be misleading in this sector of the Apenninic chain.