DATE:

Friday, September 24, 2021

TIME:

3:30 PM

LOCATION:

Virtual Zoom Conference

SPEAKER:

Dr. Shuo Ma, Geological Sciences, San Diego State University

ABSTRACT:

The Sanriku coast hosted several of the most devastating tsunami in recorded history of Japan, including the 1896 Sanriku tsunami and 2011 Tohoku tsunami. The runup on the Sanriku coast in both tsunamis were up to 40 m. It is unclear why such large runup can occur. Large near-trench slip north of 38.5°N in the Japan Trench were inferred to generate the devastating 2011 tsunami on the Sanriku coast, which is, however, inconsistent with the bathymetry observations. Here we show that the inelastic failure of wedge sediments north of 38.5°N due to dynamic stress can generate efficient short-wavelength seafloor uplift with diminishing slip at the trench, consistent with the bathymetry observations, which produces impulsive (short-period) tsunami that can be amplified by the rugged Sanriku coast. An inelastic wedge deformation model of the 1896 Sanriku earthquake is shown to generate impulsive tsunami similar to what was observed offshore the Sanriku coast in the 2011 Tohoku tsunami and produce tsunami runup remarkably consistent with the observed runup of the 1896 Sanriku tsunami. Dynamic failure of thick wedge sediments north of 38.5°N in the Japan Trench likely plays an important role in the generation of the devastating 2011 Tohoku tsunami.

HOST:

Jose Castillo

VIDEO: