Constant monitoring of faulted regions with seismographs and space geodesy measurements can indicate when land deformations are occurring close to the surface. But for subduction zones, much of the deformation occurs deep within Earth, making it difficult to detect from the surface.
In a new study, Panet et al. investigate whether they could detect slab deformations using gravity measurements from satellites. They used Gravity Recovery and Climate Experiment (GRACE) satellite data. This data can show information about changes in Earth systems, including amounts and locations of water and ice as well as crustal deformations.
In previous studies, the team identified and mapped anomalous variations in Earth’s gravity in the months preceding the Tohoku earthquake. For this study, the researchers developed a new way to detect signals along plate boundaries.
The team used GRACE to study subtle changes in gravity in subduction systems. Using overlapping passes of GRACE gravity measurements from 2004 to 2011, the team tested whether they could see deep signals in the solid Earth before Tohoku occurred, and created a method to identify solid mass redistributions based on the variation of gravity gradients.
They found there were unique gravity signatures preceding the Tohoku earthquake, most likely associated with deep deformations in the subduction system. The team says their work shows a way to continuously monitor Pacific plate subduction movements at depth using real-time gravity-measuring satellites.
https://phys.org/news/2022-09-months-gravity-thoku-earthquake.html