Earthquake early warning using future generation gravity strainmeters

Abstract

Recent studies reported the observation of prompt elastogravity signals during the 2011 M9.1 Tohoku earthquake, recorded with broadband seismometers and gravimeter between the rupture onset and the arrival of the seismic waves. Here we show that to extend the range of magnitudes over which the gravity perturbations can be observed and reduce the time needed for their detection, high‐precision gravity strainmeters under development could be used, such as torsion bars, superconducting gradiometers, or strainmeters based on atom interferometers. These instruments measure the differential gravitational acceleration between two seismically isolated test masses and are initially designed to observe gravitational waves around 0.1 Hz. Our analysis involves simulations of the expected gravity strain signals generated by fault rupture, based on an analytical model of gravity perturbations in a homogeneous half‐space. We show that future gravity strainmeters should be able to detect prompt gravity perturbations induced by earthquakes larger than M7, up to 1,000 km from the earthquake centroid within P waves travel time and up to 120 km within the first 10 s of rupture onset, provided a sensitivity in gravity strain of 10^(−15) Hz^(−1/2) at 0.1 Hz can be achieved. Our results further suggest that, in comparison to conventional P wave‐based earthquake‐early warning systems, gravity‐based earthquake‐early warning systems could perform faster detections of large offshore subduction earthquakes (at least larger than M7.3). Gravity strainmeters could also perform earlier magnitude estimates, within the duration of the fault rupture, and therefore complement current tsunami warning systems.