Long-Lived Tsunami Edge Waves and Shelf Resonance From the M8.2 Tehuantepec Earthquake

Abstract

The 8 September 2017 M8.2 Tehuantepec, Mexico, earthquake ruptured an ~150-km-long high-angle normal fault below the subduction zone megathrust. A tsunami was generated by the event with surveyed runup as large as 3 m. Tide gauges in the region show a remarkably long duration of the tsunami with oscillations within the very wide and shallow Tehuantepec shelf lasting as long as 3 days. Here we produce a model of the tsunami and validate it by comparing it to the tsunami survey and to the time and frequency domain features of regional tide gauges. We analyze the model results and show that the long-lived oscillations are a result of wholesale resonance of the shelf as well as very efficient trapping of edge waves at the shore. These resonant features are the result of the Tehuantepec shelf morphology and illuminate a previously unidentified tsunami hazard for the region.