Can Inelastic Wedge Deformation Explain the Large Tsunami Runup of the 1896 Sanriku Earthquake?

Session: Understanding Non-Traditional Seismic Tsunami Hazards [Poster]
Type: Poster
Date: 4/28/2020
Time: 08:00 AM
Room: Ballroom
Description: 

The 1896 Sanriku earthquake (~M_W8) is a classic tsunami earthquake, which generated weak ground shaking, but the resulted tsunami heights on the rugged Sanriku coast were at least comparable to (if not larger than) those produced by the 2011 M_W 9 Tohoku earthquake, killing more than 22,000 people. In order to explain the large tsunami heights along the Sanriku coast in 2011, elastic dislocation models require large trench slip (up to 36 m) more than 100 km north of the epicenter. However, the bathymetry data before and after the 2011 earthquake in the region suggest no large trench slip or submarine landslides (Fujiwara et al., 2017). Ma and Nie (2019) showed that inelastic wedge deformation can efficiently generate seafloor uplift, but reduce near-trench slip, which is more consistent with the bathymetry data. Here we simulate tsunami runup of the 1896 Sanriku earthquake by using the seafloor uplift results of Ma and Nie (2019) for M_W 8 and high-resolution bathymetry data. We will show that the short-wavelength seafloor uplift (~20 km) by inelastic wedge deformation can interact more efficiently with the rugged bathymetry offshore of Sanriku to amplify the tsunami heights than the broader uplift caused by elastic dislocation on the plate interface. These results will have important implications for the physical understanding of the 2011 Tohoku tsunami given the similarity of these two tsunamis on the Sanriku coast.

Presenting Author: Yue Du

Authors