Globally Scattered 2011 Tohoku Tsunami Waves From a Seafloor Sensor Array in the Northeast Pacific Ocean

• Published in: Journal of Geophysical Research: Solid Earth
• Main Authors: Kohler, Monica D., Bowden, Daniel C., Ampuero, Jean Paul, Shi, Jian
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: American Geophysical Union 2020
• Subjects: tsunami; beamforming; backprojection; scattering; 2011 Tohoku earthquake; pressure gauge array; Pacific; Scripps; Antarc*; Antarctica
• Online Access: https://doi.org/10.1029/2020jb020221

Modeling of tsunami wave propagation for forecasting focuses on the arrival time and amplitude of the earliest tsunami waves reaching coastlines. The complex later tsunami wavefield, in which scattering is predominant, poses additional hazards due to possible constructive interference of coherent packets of wave energy. However, almost no data sets exist to characterize the geographical sources and temporal evolution of the scattered waves. Here we show how recordings of the 2011 Tohoku tsunami by an array of pressure gauge sensors in the northeastern Pacific Ocean reveal coherent waves that are produced by scattering from distant coastlines including South America and Antarctica, as well as multiple seafloor fracture zones, ridges, and island chains. Multiple signal classification analysis and backward propagation ray tracing provide tight constraints on the origin of each scattered phase and resolve simultaneous wave arrivals from different scatterers. Incoming waves from constant back azimuths occur over time durations of several hours, revealing the time persistence of specific geographical scatterers. The results can advance numerical predictions of tsunami wave impact because they provide direct evidence for the necessity of incorporating both local and distant bathymetry over a range of length scales and for long time durations, to account for the azimuthal dependence of scatterer strength. © 2020 American Geophysical Union. Issue Online: 13 November 2020; Version of Record online: 13 November 2020; Accepted manuscript online: 30 October 2020; Manuscript accepted: 25 October 2020; Manuscript revised: 20 October 2020; Manuscript received: 19 May 2020. This manuscript greatly benefitted from thoughtful reviews provided by Frank González and an anonymous reviewer. The OBS deployment was made possible with instruments and logistical support of the Ocean Bottom Seismic Instrumentation Pool at Scripps Institution of Oceanography. The ALBACORE OBS deployment and recovery cruises were made possible with the ...