Ground Motion Validation of the 1923 Kanto Earthquake Using the New Geometry of the Philippine Sea Slab and Integrated 3D Velocity-Structure Model

The Tokyo metropolitan area is under constant threat of strong ground motions from future plate-boundary earthquakes along the subducting Philippine sea slab. Here, we upgrade a ground motion simulation of the 1923 Kanto earthquake using a source model along the new geometry of the Philippine sea slab, geophysical-based velocity model, and effcient computational tool. The source process was inferred from strong-motion, teleseismic, and geodetic data with the new geometry of the slab. The 3D velocity-structure model beneath the Tokyo metropolitan area has been constructed using integrating refraction, reflection, borehole, microtremor, and gravity data, as well as ground motion spectra. We introduce a low-frequency ground motion simulation using these models and the finite element method with a voxel mesh. The western basin edge complicated wave propagation, and excited long-period motions were found within the basin. We confirmed that the simulated ground motions are sensitive to the distribution of asperities of the source model along the shallower plate geometry where the eastern major asperity is located closer to downtown Tokyo than in previous models. Because high-frequency components are essential for seismic intensity measurements, source modeling using the pseudo-dynamic approach and ground-motion simulation using the hybrid method combining deterministic and stochastic approaches are strong candidates to complete a broadband ground motion simulation