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A powerful tsunami triggered by the Mw 9.0 Tohoku earthquake struck the northern Pacific coast of Japan in 2011, destroying several coastal communities in Iwate Prefecture, Miyagi Prefecture, and Fukushima Prefecture. Here, we investigate a new spatio-temporal slip model (model B) developed by the Cabinet Office of the Government of Japan. This slip model was compared against the non-uniform slip model estimated using tsunami waveform data (model A). We focused our analysis on two areas that were destroyed by the tsunami. The town of Onagawa and the coastal Sendai Plain area were selected because they were located in front of the epicentre, where the most significant slips were registered. Our simulation results revealed that the spatio-temporal slip distribution better replicated the observed data. Regarding the tsunami waveforms from the coastal tide gauge station and offshore stations, the Cabinet Office's slip model showed an approximately 30% better accuracy relative to the non-uniform slip model. Furthermore, by comparing the local inundation features at two locations with unique topographic and coastal morphological characteristics, we also found that model B better replicated the measured inundation depths. Finally, considering that tsunami-induced damage is a direct function of various inundation features such as the flow depth and flow velocity, this new slip model can generate more realistic damage scenarios for future tsunami assessments. [ABSTRACT FROM AUTHOR]

Propagation and inundation characteristics of the 2011 Tohoku tsunami on the central Sanriku coast are investigated through field surveys and numerical simulations using offshore wave recordings as incident wave conditions. The numerical model successfully reproduces the extent of flood areas as well as the distribution of tsunami heights along the intricate coastline except for run-up of extreme heights over steep slopes. The survey and computed results suggest significant variations of tsunami heights along the coastline. Their positive dependency on topographic slopes implies that the incoming tsunami propagates in standing wave mode to precipitous sites while in progressive wave mode accompanied by wave breaking over gentle slopes. Temporal-spatial analysis of wave properties in different bays reveals that the inner bay topography provides a clear contrast to inundation characteristics. The impacting waves have extreme heights due to the funnel effect and local wave resonances causing highly transient flooding in narrow V-shaped bays whereas tsunami surges over longer periods across innermost shores of U-shaped bays to produce large horizontal velocities during both run-up and backwash phases. [ABSTRACT FROM AUTHOR]

On March 11, 2011, at 14:46 local time, a powerful earthquake occurred off the Sanriku coast of northeastern Japan. It was immediately apparent that this was the strongest earthquake on the historical record, and the resulting series of tsunami ravaged the Tohoku region. In Iwate Prefecture, the tsunami height generally exceeded the design tsunami level for safety, which had been determined on the basis of the 1896 Meiji-Sanriku tsunami, the 1933 Showa-Sanriku tsunami, and the 1960 Chile tsunami. As of January 10, the number of dead and missing in Iwate rose to 6,035. Over 24,000 buildings had been destroyed. After the 1933 Showa-Sanriku, disaster prevention facilities were built along the coast. However, many tsunami seawalls and water gates suffered enormous damage from the impact of the 2011 Tohoku Tsunami. This paper sketches out the characteristics and scope of the damage in the coastal areas of Iwate Prefecture, with a particular focus on the northern coast of Iwate. [ABSTRACT FROM AUTHOR]