GPS surveys in the foreland-foredeep tectonic system of Southeastern Sicily:first results

M Anzidei M Anzidei,B Puglisi B Puglisi,M Mattia M Mattia,G Casula G Casula,S Gresta S Gresta,G Puglisi G Puglisi,A Pesci A Pesci,A Galvani A Galvani,O Campisi O Campisi,A Bonforte A Bonforte

doi:10.4401/ag-3533

Abstract

The Hyblean plateau (Southeastern Sicily) is characterised by three main tectonic structural trends: the first, NNW-SSE striking, runs on the easternmost part of the plateau and is linked to the Hyblean-Maltese fault system; the second runs along the western part of the plateau with a NNE-SSW direction and is characterised by a sinistral strike slip motion, like the Scicli fault; the third ENE-WSW striking, characterises the northernmost part of the area, including the Scordia-Lentini graben. We analysed GPS data collected in a dense network located in the northern area of the Hyblean plateau during 1998 and 2000, between the towns of Catania and Syracuse. Data from Noto, Matera and Cagliari IGS stations, were included in the processing to connect this network to the International Terrestrial Reference Frame (ITRF). The comparison between 1998 and 2000 data sets shows an average northward motion of the GPS stations located south of the Gela-Catania foredeep. Site velocities decrease from south to north and show a weak internal deformation of the northernmost part of the Hyblean plateau.

Highlights

The main geological structures of Eastern Sicily are represented by: i) the crystalline units of the Calabrian arc, which belong to the innermost unit of the chain; ii) the MaghrebianThe Hyblean plateau belongs to the northernmost part of the Pelagian block which extends southward to the Malta islands (Ben Avraham et al, 1990)
Seismicity is characterised by lower magnitudes (M < 5) on the western side of the Hyblean plateau with respect to its northern (M ≈ 6) and eastern (M ≈ 7) areas, where destructive earthquakes occurred in 1169 and 1693
It is worth noting that the latter was proceeded by a strong foreshock of M ≈ 6 which likely occurred along the same seismogenetic structure that produced an earthquake of M≈ 6.5 in 1542, identified as the southern fault of the Scordia-Lentini graben (Azzaro and Barbano, 2000)

Summary

Introduction

The main geological structures of Eastern Sicily (fig. 1) are represented by: i) the crystalline units of the Calabrian arc, which belong to the innermost unit of the chain; ii) the Maghrebian. Along the Ionian margin a dense fault pattern form onshore a horst and graben sequence, oblique with respect to the Hybleo-Maltese escarpment, while the northern edge of the Hyblean plateau facing the northern foredeep areas is down faulted by NE-SW trending normal faults, forming structures as the Scordia-Lentini graben (Adam et al, 2000) This complex structural setting plays an important role in the recent seismic activity of the area, characterised by major earthquakes along the western, northern and eastern boundaries of the Hyblean plateau. On December 13, 1990 the area was struck by a ML = 5.4 seismic event occurring offshore from the town of Augusta, which produced widespread damage between Syracuse and Catania This is the only earthquake for which instrumental data are available, the seismogenic structure cannot clearly be identified due to the ambiguous fault plane solutions (Amato et al, 1995; Giardini et al, 1995). GPS surveys in the foreland-foredeep tectonic system of Southeastern Sicily: first results

Geodetic networks and surveys

IAZZ IIV IAZZ IIV IAZZ IIV IP12 IIV

GPS data processing and analysis of the results

Discussion and conclusions