Capable Faults of the Eastern Etna Region and Reduction of their Environmental Hazard: An Application of the ITHACA database
by
Luca Ferreli
APAT (Italian Agency for Environment Protection and Technical Services), via Vitaliano Brancati 48, 00144 Roma
Coauthors: D. Bella, A.M. Blumetti, P. Di Manna, F. Filetti, D. Fiorenza, G. Luberti, G. Masella, R. Serafini, E. Vittori

We present the new map of capable faults of the Etna volcano region (Eastern Sicily), compiled within the frame of the ITHACA (Italy Hazard from Capable Faults) project. This project, carried out by APAT-Geological Survey of Italy, aims at building up an updated database and GIS of capable faults (i.e., active faults able to produce significant deformation at or near the ground surface) affecting the Italian territory, analyzed in terms of their seismic and environmental hazard potential.

The eastern flank of the Etna volcano is characterised by frequent, low magnitude and very shallow seismic events. Common hypocentral depths are shallower than 1-2 km, hence within the volcanic blanket, which rests on a relatively shallow clay basement. Therefore, notwithstanding the small magnitude, this seismic activity is able to induce noteworthy ground surface effects. At the same time, frequent creep phenomena take place along well-defined structures, either or not associated to seismic events and/or volcanic eruptions.

Consequently, these surface deformations are commonly interpreted as the result of the interaction between regional tectonics (along the Ibleo-Maltese and Messina-Fiumefreddo fault systems) and local volcano-tectonic and gravitational processes.

The area affected by surface ruptures is bounded to the north by an east-west trending fault system (Pernicana and Fiumefreddo faults) and to the south, in a more subdued way, by the Tre Castagni and Tre Mestieri--Nicolosi fault systems. Such region is slowly sliding toward the Ionian basin (lateral spreading), probably in response both to fault movements along the Ibleo-Maltese fault system and to the periodic pulses of the Etna magmatic chamber.

This sector of the volcano apparatus is sharply characterized by NNW-SSE trending tectonic terraces, tens to hundreds of meters high, generated by normal to normal-dextral faults belonging to the so-called Timpe system. Being these faults well-aligned with the northern projection of the Ibleo-Maltese fault system, many authors, ourselves included, consider them as part of it. This has relevant implications in terms of the local seismic hazard, considering that the Ibleo-Maltese fault system is the suspected source of the 1693 M 7.4 earthquake, giving the possibility for much deeper and energetic seismic events in the Etna region, as indicated also by the 1818 M 6 earthquake.

Coseismic surface faulting events and creep phenomena (not always clearly understood by local administrations) are responsible for heavy effects on human structures, such as buildings, roads, railways and lifelines. For example, the survey of the ground effects caused by the 2002 volcano-tectonic events, jointly performed by APAT and the Sicilian environmental agency (ARPA) has pointed out many damages to the water supply network.

To provide a useful tool for the reduction of the environmental effects of faulting, APAT is now compiling a georeferenced database, where capable faults and water supply as well as other environmentally-sensible networks can be overlapped and intersections (zones of expected peak damage and failure) easily evidenced.

Date received: July 22, 2005

Copyright © 2005 by the author(s). The author(s) of this document and the organizers of the conference have granted their consent to include this abstract in Atlas Conferences Inc. Document # caqy-49.