https://techcrunch.com/2022/05/05/gps-signals-could-detect-tsunamis-better-and-faster-than-seismic-sensors/

GPS networks are already a crucial part of everyday life around the world, but an international team of scientists has found a new, potentially life-saving use for them: tsunami warnings.

Researchers from University College London and universities across Japan studied the ability of the GPS network to detect tsunamis, concluding that instruments can indeed detect the destructive waves from space. They’ve also determined that GPS can provide more detailed information than current detection systems — at an extremely low cost — allowing authorities to issue more accurate warnings in advance of a tsunami’s impact on shore.