Ground Effects during the 9 September 1998, Mw = 5.6 Lauria Earthquake and the Seismic Potential of the "Aseismic" Pollino Region in Southern Italy

Abstract

On 9 September 1998, at 13:28 local time (11:28 UTC), a moderate earthquake of Mw = 5.6 struck the Southern Apennines at the northwest margin of the Pollino Massif (the highest mountain range of the region, reaching elevations above 2,000 m a.s.l.; Figures 1 and 2). The macroseismic epicenter is located about 3 km southeast of Lauria, with a maximum intensity of VIII on the MCS scale (or MM or MSK; see below for a correlation among macroseismic scales); thus we refer to this event as the Lauria earthquake. Historical towns—such as Lagonegro, Lauria, and Castelluccio—suffered significant damage, in particular that of Rivello, which is a remarkable local artistic site. Several ground effects followed the shock, and a rockfall on the road between Cersuta and Acquafredda (site 9a in Figure 3) claimed one life. A moderate magnitude event, the Lauria earthquake, together with the 5 May 1990 Potenza earthquake ( Ms = 5.4), was the largest earthquake in southern Italy since the destructive 23 November 1980 Irpinia earthquake (Alessio et al., 1995, cum bib.; Table 1 and Figure 2A). The day after the shock we initiated a reconnaissance survey of the epicentral area in order to record the geological and environmental changes induced by the earthquake. Among many other effects, we observed the rejuvenation of a bedrock fault scarp. In this paper we focus on this evidence of tectonic surface rupture because it has significant implications for the seismic hazard assessment both in (a) this sector of the Apennines and (b) other parts of the world. 1. This is the first modern observation of earthquake surface rupture in the apparently “aseismic” Pollino region. Figure 2 shows that according to the historical seismic catalogs only a few moderate to small local earthquakes (I ≤ VIII MCS) affected this area, in …