Reevaluating Large‐Scale Deformation Precursors of Great Subduction Earthquakes: Insights From Satellite Gravity and GNSS Data

Abstract Validating the controversial hypothesis that precursory gravity changes arise from sudden acceleration of subducting plates potentially triggering great earthquakes is of paramount importance. To rigorously evaluate proposed precursors for the 2011 Mw 9.0 Tohoku and 2010 Mw 8.8 Maule earthquakes, we develop a statistical framework that enables (a) robust assessment of their statistical significance, (b) characterization of temporal evolution, and (c) integrative analysis across multiple GRACE gravity solutions with differing error characteristics. Additionally, we test the precursor hypothesis using independent GNSS‐measured surface displacements within a physically consistent framework. Our results show no evidence supporting the proposed precursor in either alternative GRACE solutions or high‐precision GNSS observations. The anomalous gravity changes previously interpreted as earthquake precursors are indistinguishable from solution‐specific data errors or other non‐tectonic signals, lacking evidence for tectonic origin.