Maps showing the data assimilated wavefields at 30 and 120 seconds on the left and the forecasted future wavefields at 200 seconds on the right
Left: the data assimilated wavefields at 30 and 120 seconds. Right: the forecasted future wavefields at 200 seconds. Credit: Oba et al. [2020], Figure 4, top and bottom panels
Source: Journal of Geophysical Research: Solid Earth

Large earthquakes can generate long-period (LP) ground motions, surface waves that can travel large distances and cause significant damage to buildings and infrastructure many hundreds of kilometers from the epicenter.

One place where this is particularly pertinent is Japan. The Nankai Trough subduction zone off the southwest coast of Japan has been the source of a number of large earthquakes over recent centuries and the next one is expected in the coming decades. This poses a tremendous threat to large urban populations and physical infrastructure, including the greater Tokyo region.

Oba et al. [2020] carried out numerical tests using motion records from a past earthquake (the 2004 Off Kii Peninsula earthquake) together with simulated seismograms of potential large earthquake scenarios in the Nankai Trough. Their approach is a major advance because it combines direct assimilation of observed data with full accounting for the important effects of 3D basin structure.

This method, making use of advanced high-performance computing technology, has the potential to provide advance warning of ground shaking in real time, thereby buying valuable time for damage mitigation actions.

Citation: Oba, A., Furumura, T., & Maeda, T. [2020]. Data assimilation‐based early forecasting of long‐period ground motions for large earthquakes along the Nankai Trough. Journal of Geophysical Research: Solid Earth, 125, e2019JB019047.

—Masumi Yamada, Associate Editor, JGR: Solid Earth

Text © 2020. The authors. CC BY-NC-ND 3.0
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