Low Energy Sequences in Areas with High Seismic Potential: Benevento (Southern Apennines), April 1990

In the southern sector of the Apennines chain (Italy), destructive earthquakes with medium-high magnitude occurred within a narrow belt along the axis of the chain. Low-energy seismic swarms have frequently been observed.The Sannio area and particularly the Benevento province, was hit by strongly destructive events of I ≥ IX MCS (1456, 1688, 1702, 1732, 1930, 1962), as well as by seismic swarms (1885, 1903, 1905).A seismic sequence started in April 1990 near the town of Benevento. This sequence was studied in detail through the analysis of data recorded by temporary seismic networks installed in the area and operating for about two months. Over 300 microearthquakes were located in a small area of about 100 km2, close to the town of Benevento. Cross sections of hypocenters indicate that the depths of the events were concentrated within the first 15 km of the crust.The maximum seismic energy was released at the beginning of the sequence, with the highest magnitude M_L = 3.6. Most events were felt by the population, but they caused no damage.Fault plane solutions calculated for a selected number of events show that most of the mechanisms have T axes oriented in an anti-apenninic direction (NE-SW).In this paper a small sequence is analyzed in order to evaluate its relations with the strongest earthquakes and the tectonic lineaments associated with them, for seismic hazard assessment.