The first detections of gravitational waves by the LIGO-Virgo network marked the beginning of gravitational-wave astronomy. While LIGO and Virgo will continue taking data in the next years, the Japanese detector KAGRA and LIGO India will join the network. Substantial technology upgrades of the current detectors are being envisaged in the mid 2020. In parallel, much more sensitive detectors, hosted in new infrastructures, are being studied: the European Einstein Telescope (ET), and the US Cosmic Explorer (CE).
Current Earth-based gravitational-wave detectors are limited by seismic noise at a few Hz. However, very interesting gravitational-wave sources are expected below 1Hz. Hence efforts are ongoing to study the feasibility of sub-Hz Earth-based gravitational-wave detectors.
In this seminar the problem of Newtonian Noise is addressed, which is one of the main noise in ground based gravitational wave detectors at low frequencies (below 20 Hz). Furthermore, a possible geophysical application of sub-Hz Earth-based gravitational-wave detectors is presented, i.e. the application in earthquake early warning systems, as well as aspects of the experimental development of one of the sub-Hz detector configurations, i.e. the torsion bar antennas case.