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Data Assimilation‐Based Early Forecasting of Long‐Period Ground Motions for Large Earthquakes Along the Nankai Trough
Author(s) -
Oba Atsuki,
Furumura Takashi,
Maeda Takuto
Publication year - 2020
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.983
H-Index - 232
eISSN - 2169-9356
pISSN - 2169-9313
DOI - 10.1029/2019jb019047
Subject(s) - seismology , geology , seismogram , data assimilation , trough (economics) , strong ground motion , meteorology , ground motion , geodesy , geography , economics , macroeconomics
Long‐period (LP) ground motions with periods of ~2–10 s caused by large earthquakes are strongly amplified in sedimentary basins, posing serious threats to modern cities to cause resonance and damage to skyscrapers, oil storage tanks, long‐span bridges, and other structures with long natural periods. Since the LP ground motions are composed of surface waves traveling for longer distances with much slower speeds than body waves, an alert could be issued by detecting the spread of strong ground motion near the source and before large ground motions occur in distant basins. In this study, an early forecasting of LP ground motions is proposed based on data assimilation of observed ground motions obtained by high‐density, nationwide seismic networks and a computer simulation of the seismic wave propagation using a high‐resolution subsurface structure model. The shaking of the LP ground motions in the distant basins is immediately forecasted by high‐speed supercomputers from current data‐assimilated wavefield. In addition, the forecasting speed is significantly improved by using Green's functions, representing the wave propagation response from the data assimilation stations to a forecast target site. The effectiveness of this data assimilation‐based forecasting of LP ground motions in conjunction with using Green's functions is demonstrated by numerical tests using the observed strong motion records from the 2004 Off Kii Peninsula earthquake in Japan (Mw 7.4) together with synthetic seismograms of anticipated large earthquake scenarios in the Nankai Trough.