A Seismogeodetic Amphibious Network in the Guerrero Seismic Gap, Mexico

The historical record of large subduction earthquakes in Guerrero, Mexico, reveals the existence of an ∼230
km length segment below the coast where no major rupture has occurred in the past 60 years. Reliable quantification of the hazard associated with such a seismic gap is urgently needed for risk mitigation purposes by means of state-of-the-art observations and modeling. In this article, we introduce and quantitatively assess the first seismogeodetic amphibious network deployed in Mexican and Central American soils that will provide the opportunity to achieve this goal in the near future. Deployed in 2017, the network is the result of a collaborative effort between Mexican and Japanese scientists. It consists of 15 onshore broadband and 7 ocean-bottom seismometers, 33 Global Positioning System (GPS) stations, 7 ocean-bottom pressure gauges, and 2 GPSacoustic sites, most of them installed within the Guerrero seismic gap. Initial data from the network revealed the occurrence of a 6-month-long slow-slip event in Guerrero, starting in May and ending in October 2017. To illustrate the performance of the various instruments, we also present the first ocean-bottom pressure and GPS-acoustic measurements in Mexico; the latter was obtained by means of an autonomousWave Glider vehicle. The ground motion of the devastating 19 September 2017 Mw 7.1 earthquake in central Mexico is presented as well. Nominal resolution of the seismogeodetic network is estimated through different synthetic inversion tests for tomographic imaging and the seismic coupling (or slow-slip) determination on the plate interface. The tests show that combined onshore and offshore instruments should lead to unprecedented results regarding the seismic potential (i.e., interface coupling) of the seismic gap and the Earth structure from the Middle America trench up to 70-km depth across the Guerrero state.