Shallow subsurface geology and seismic microzonation in a deep continental basin. The Avezzano Town, Fucino basin (central Italy)

Abstract. We present detailed geological investigations aimed at the reconstruction of the shallow subsurface geology, and associated local seismic hazard, of the Avezzano town in the Quaternary Fucino basin (central Apennines). This work shows a basic (Level 1) seismic microzonation (SM) of the Avezzano town, focusing the attention on geologic constraints. We also discuss some methodological procedures of SM.

Level 1 SM involves a reconstruction of the subsurface geological model achieved by a multidisciplinary approach synthesized in two main thematic maps and geologic sections. The first map, containing essential geologic information, is formed by overlapping layers (geological units, litho-technical units, and geomorphological/structural features). The second map is a summary map, easily accessible to non-geologist earthquake scientists/technicians, which synthesizes surface geology, subsurface data and resonance frequencies into homogeneous microzones. The two maps are tools for land and urban planning.

The Avezzano area provides a case study of shallow subsurface geology and site effects in a deep continental basin environment, and is of potential interest for similar geologic contexts worldwide. Within the investigated area, almost all the possible earthquake-induced effects can occur, such as (a) stratigraphic amplifications in a wide range of resonance frequencies (from 0.4 to > 10 Hz); (b) liquefaction; (c) coseismic surface faulting; (d) basin-edge effects; and (e) slope instability.