GNGTS 2014 - Atti del 33° Convegno Nazionale

GNGTS 2014 S essione 1.1 69 the seismic monitoring network in the Pollino region in order to lower the detection threshold of the network and improve the hypocentral locations of small earthquakes. One permanent station of the Italian Seismic Network was installed to the south along the Tyrrhenian coast, 3 real time (UMTS transmission) temporary stations were deployed and 2 stand alone stations. At the end of May 2012, after the occurrence of the M L =4.3 event, two other temporary stations transmitting in real time to the INGV monitoring room were deployed. At the end of July 2012 the first temporary stations were removed leaving only the two real time stations installed at the end of May 2012 (Amato et al. , 2012). Between the end of October and the beginning of November 2012, after the M L =5.0 earthquake, an international research team by the INGV and the German Research Centre for Geoscience (GFZ) installed 15 seismic stations and an array to improve the detection capabilities of the INGV permanent network giving us the opportunity to refine the location of the earthquakes hypocenters.. Six stations costitute the small aperture seismic array (Govoni et al. , 2013) The activated fault system. A combined dataset, including three-component seismic waveforms recorded by both permanent and temporary stations, has been analyzed in order to obtain appropriate 1D and 3D velocity models for earthquakes location in the study area. We produced refined locations by means of Hypoellipse (Lahr, 1989) for events recorded from October 2011 to March 2013 using waveforms of temporary stations installed during the seismic sequence. In order to compute the final 1D velocity model we apply the inversion scheme introduced by Kissling et al. (1994) and implemented in the code VELEST to an optimal sample of seismicity, representative of the seismogenic volume. We plot in figure 3 only events with small location errors (smaller tha 1km). Refined earthquakes locations allowed us to infer the geometry of the faults relative to the two strongest shocks and to image the entire activated fault system. The seismicity is mainly Fig. 2 – Seismic network running in the Pollino region during the seismic sequence. The different symbols for the different stations are explained in the legend; the stars are the epicenters of the two mainshocks. Inset pictures show the seismic stations and the geometry of the GFZ array.