Earthquake Early Warning System for Virgo: a design study

Abstract

The Virgo interferometer was able to reach its design sensitivity thanks to the performance of the seismic superattenuators. However, the ground shaking due to earthquakes both from regional and teleseismic distances can significantly affect the instrument duty cycle, especially during extended observational runs like the imminent O3.A strong event in proximity to the site could even threaten the delicate fused-silica suspensions.A fast, reliable Earthquake Early Warning system (EEWS) should issue an alert of incoming ground shaking leaving enough time to take appropriate counteractions to limit uncontrolled and unwanted oscillations of test masses. First we analyse the effects of past and present earthquakes at Virgo site with the goal to assess the relevant parameters (like distance, magnitude, azimuth) of the events able to cause significant shaking.This is accomplished using data recorded during the O2 run from seismometers located in the Virgo buildings integrated by data from italian seismic network from INGV.Then we present some ideas about the implementation of an EEWS and its requirements in term of new technologies to be developed within the framework of INGV and Ego Virgo collaboration. The aim is to define the most appropriate EEWS schema in order to maximize both safety and duty cycle of the interferometers for the case of local, regional and teleseismic earthquakes.