Sannio-Matese Mounts (Southern Italy) deformation field from GPS Data (2002-2014)

Abstract

A ML=4.9 earthquake occurred in the Sannio-Matese area at 18:08 on December 29 2013. The epicenter was located in the “Monti del Matese seismic district”. The epicentral area lies between the small towns of San Gregorio Matese, Cusano Mutri, Gioia Sannitica, Piedimonte Matese, San Potito Sannita in the Caserta province in an area with an high seismic Hazard. The area was struck by large and destructive earthquakes in the past (1456, 1688, 1702, 1732, 1805,1962) with maximum magnitude up to 7.2. Past and recent seismicity of the area is generally characterized by both single events and low energy seismic sequences (1885, 1903, 1905, 1990, 1992, 1997). The last sequence occurred on 1997 with the largest event (MD = 4.1, 19 March) occurred at the border between the Benevento and Campobasso provinces followed by an intense activity ended only in September of the same year. The epicentral distribution of the 1997 low energy (M ≤ 4.0) seismic sequence is mainly NE-SW oriented suggesting the activation of anti-Apennine faults. The December 29 2013 seismic event, is located very close to the 1688 earthquake area. Still open debate is the association of the main event of the sequence and its aftershocks with the seismogenic structures present in the area. The SAGNET (Southern Apennine Geodetic NETwork) is the Non-permanent GPS network covering the area between the Matese Mounts and the Mainarde–Meta Mountains and consists of 40 3D GPS vertices. GPS dataset consists of data recorded at non-permanent stations in the time spam 2002-2014 and at the Continuous GPS stations (CGPS) of the RING network (managed of INGV) located in the central and southern Apennines regions. We have calculated the GPS velocity field with permanent and non-permanent stations (with time series of at least 3 surveys). The horizontal velocity field, expressed with respect to a fixed Eurasian plate, shows a good coherence between the velocities field estimated from the SAGNET and CGPS. In this paper we have evaluated the strain rate in the Sannio-Matese area. Before the earthquake, GPS data analysis showed a decrease in the velocity in the southern sector of Matese Massif (where the December 29 2013 earthquake epicenter will be localized) with respect to the surrounding areas which is also evident from the lower values of the strain rate ranging between 15÷20 *10-9 yr-1. Lower GPS Strain rate has been recognized at the end of seismic cycle and appear as a useful tool to point out hazardous seismic areas as already highlighted in the 2009 L'Aquila and in the 2012 Emilia earthquakes.