Rapid identification of tsunamigenic earthquakes using GNSS ionospheric sounding

The largest tsunamis are generated by seafloor uplift resulting from rupture of offshore subduction-zone megathrusts. The rupture of the shallowest part of a megathrust often produces unexpected outsize tsunami relative to their seismic magnitude. These are so called ‘tsunami earthquakes’, which are difficult to identify rapidly using the current tsunami warning systems, even though, they produce some of the deadliest tsunami. We here introduce a new method to evaluate the tsunami risk by measuring ionospheric total electron content (TEC). We examine two Mw 7.8 earthquakes (one is a tsunami earthquake and the other is not) generated in 2010 by the Sunda megathrust, offshore Sumatra, to demonstrate for the first time that observations of ionospheric sounding from Global Navigation Satellite System (GNSS) can be used to evaluate the tsunamigenic potential of earthquakes as early as 8 min after the mainshock.Ministry of Education (MOE)National Research Foundation (NRF)Published versionSome of the results presented here are reported in the PhD thesis of Dr. Fabio Manta (https://hdl.handle.net/10356/107577), archived by Nanyang Technological University, Singapore. We are grateful to the many scientists and field technicians who have kept the SuGAr network in operation. These include Paramesh Banerjee, Iwan Hermawan, Danny Natawidjaja, Jeffrey Encillo, Imam Suprihanto, Dudi Prayudi, and Bambang Suwargadi. SuGAr GPS data are available for download from ftp://ftp.earthobservatory.sg/SugarData. This research was supported by the National Research Foundation Singapore under its Singapore NRF Investigatorship scheme (Award No. NRF-NRFI05-2019-0009) and by the EOS and the National Research Foundation Singapore and the Singapore Ministry of Education under the Research Centres of Excellence initiative. G.O. is supported by Programme National de Télédétection Spatiale (PNTS), grant n PNTS-2014-07; by the CNES, grant GISnet&Back; and by the Institut Universitaire de France (IUF). We thank Benoit Taisne for useful discussions, and the reviewers for constructive comments. This is EOS contribution 300 and IPGP contribution 4054