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  LABEX UnivEarthS GeoVirgo

Participants hors IPGP : 
APC Université Paris Diderot : Matteo Barsuglia (PI)
Eric Chassande-Mottin

Labex UnivEarthS -GeoVirgo: Geophysics and gravitational wave detectors


The detection of gravitationnal waves (GW) represents a major challenge of modern physics and particularly of the Einstein's General Relativity Theory. It makes it necessary to detect GW associated displacements of the order of  $10^{-19} m$ over a length of a few kilometers. The VIRGO detector installed close to Pisa (Italy) is an interferometer made of 2 arms with an L-shape, 3 kilometers long and it's reaching its designing sensitivity. The rate of GW astrophysical events is still small, but a big detector upgrade is planned (Advanced Virgo), which should allow a first GW detection, in collaboration with other GW projects in the world (LIGO, GEO, LCGT).  However, one basic limitation for the  gravitational wave detection is the natural seismic and environmental noise (tectonic, ocean, atmosphere, human activity) at low frequencies. In addition to the VIRGO detector, several broadband seismometers are operated. Therefore, conversely, VIRGO + seismometers can be used as a geophysical instrument and it constitutes an unique instrument and  a formidable opportunity for detecting extremely small motions within the Earth. We plan to directly calculate some components of the deformation tensor giving access to several strain and rotational components. After the estimation of the seismic noise of the different instruments (Virgo + broadband seismometers) by using classical methods, developed by the GEOSCOPE network on a routine basis, we plan  to estimate the detection threshold of the whole instrument and to search for seismic events, free oscillations of the Earth (inner core Slichter modes), tides and seismic Hum.