A new generation of high-precision gravity sensors such as torsion pendulums and atom interferometers, and future concepts for kilometer-scale gravitational-wave (GW) detectors searching for ripples in spacetime from colliding and exploding stars, will make it possible to study gravity perturbations in the frequency range 0.1Hz to 10Hz. These include terrestrial gravity perturbations that are of interest to Earth scientists, but that are considered as noise contribution in GW detectors. The applicant wants to carry out a detailed study of terrestrial gravity perturbations in the above given frequency range. The analysis will include gravity perturbations from fault rupture, and from seismic waves that are predicted to live on interfaces deep inside Earth such as the core-mantel boundary. Numerical simulations will be used to generate full gravity time series based on dynamical models of the sources and of the propagation of the seismic disturbance. This research will provide a completely new approach to understand the first minute of earthquakes. Furthermore, results from the fault-rupture analysis will be used to determine the impact that gravity sensors could have in earthquake-early warning systems. The project will also investigate terrestrial gravity noise in GW detectors with focus on the poorly understood atmospheric perturbations. Infrasound fields, convection and turbulent air flow are all expected to generate significant gravity noise in GW detectors. The goal is to create improved models for atmospheric perturbations partially based on numerical simulations. The results will be used to develop strategies to mitigate this type of gravity noise in GW detectors. The outcome of this research will have great impact on future developments of ground-based GW detection.