GNGTS 2014 - Atti del 33° Convegno Nazionale

GNGTS 2014 S essione 1.3 233 Campi Flegrei monitoring through Passive Image Interferometry. In Fig. 1 the broad band Campi Flegrei seismic monitoring mobile network operated during the three-year period between January 2010 and December 2012 is showed. We dispose of the continuous recordings from the following eleven broadband seismic stations: ACL2, ASB2, OMN2, BGNG, PESG, RENG, BULG, CELG, OVDG, SETG, MSGG. Sampling interval is 0.008 s for all stations, except for CELG, OVDG, SETG, stations that have a sampling interval of 0.01 s. The stations ACL2, ASB2 and OMN2 are equipped with Lennartz LE3D/20s sensors; stations BGNG, PESG and RENG are equipped with Guralp CMG 40T sensors; stations BULG, GELG, OVDG, SETG are equipped with Geotech KS200 sensors. First of all we operate an instrument correction because the seismic stations have different acquisition systems with different responses. In fact, ACL2, ASB2, BULG, OMN2, PESG, MSGG and RENG stations are equipped with Marslite acquisition systems; BGNG and OVDG are equipped with M24 acquisition systems; CELG with a Reftek 130 and SETG with a Taurus acquisition system. The successive step is to synchronize the traces in order to avoid any delay between instruments that would be misleading. Our data manipulation includes the interpolation of gaps when these are shorter than the 20% of one hour. These is an arbitrary choice due to the fact that often seismic data recordings are affected by very short gaps in the data (on the order of some samples); in such a way we make the data as continuous as possible. It is possible to isolate the oceanic noise source by filtering the signal in a frequency range between 0.1 and 1 Hz. Instead of a simple band pass filter we prefer to whiten the spectra of the time series in the same frequency band (Bensen et al. , 2006). Then it is important to Fig. 1 – Map of the Campi Flegrei caldera. Stations used for this study are the 11 broadband velocimeters (red triangles), which were operating continuously since 2010 (see text for more details).