Japan faces the world's highest tsunami hazard and risk due to its tectonic environment, high population density and exposure concentration along its coastlines. It is therefore of paramount interest to quantify and differentiate absolute and relative tsunami hazard and risk on a countrywide scale. We quantify tsunami hazard in terms of inundation depth for the entire Japanese coastline with a probabilistic tsunami hazard assessment utilizing the earthquake source information of the 2017 Japanese seismic hazard model. We simulate a stochastic event set for offshore earthquake sources and generate, for each single source with M_W ≥ 7.5, non-uniform finite-fault slip models. We calculate elastic seafloor and landmass deformations that serve as initial conditions to high-resolution numerical modelling of tsunami wave propagation and coastal inundations by solving the non-linear shallow water equation. Variable land surface roughness based on land cover data is used to simulate accurate hydraulics of coastal inundation.

We differentiate tsunami hazard by inundation depth hazard curves and inundation depth return period maps aggregated to city ward polygons as meaningful administrative boundaries. We find mega-thrust events on the subduction interfaces constituting the largest hazard. However, events down to M_W = 7.5 can contribute to substantial hazard in several regions along the coast. In particular for city wards within the Tokyo bay area, we find that earthquakes occurring on the Sagami trough and not the largest mega-thrust events on the Nankai trough, contribute to the highest inundation hazard. Our results also illustrate that tsunami hazard on the western Japanese coast is not negligible.

由于其构造环境，高人口密度和海岸线沿线的集中度，日本面临着世界上最高的海啸灾害和风险。因此，最重要的是在全国范围内量化和区分绝对和相对的海啸危害与风险。我们利用2017年日本地震灾害模型的地震源信息，通过概率性海啸灾害评估，根据整个日本海岸线的淹没深度来量化海啸灾害。我们为海上地震震源模拟一个随机事件集，并为每个地震震源产生M _W ≥7.5，非均匀有限故障滑动模型。通过求解非线性浅水方程，我们计算了海底和陆地的弹性变形，这些变形是海啸波传播和沿海淹没的高分辨率数值模拟的初始条件。基于土地覆盖数据的可变地表粗糙度用于模拟沿海淹没的精确水力。

我们通过淹没深度危害曲线和淹没深度返回期图（以有意义的行政边界汇总到城市病区多边形中）来区分海啸危害。我们在构成最大危害的俯冲界面上发现了巨大的推力事件。但是，低至M _W  = 7.5的事件可能会在沿海多个地区造成重大危害。特别是对于东京湾地区的城市病房，我们发现相模谷发生的地震，而不是南海谷发生的最大的特大推力事件，是造成淹没风险最高的原因。我们的结果还表明，日本西部沿海的海啸危害不可忽略。