Data Assimilation‐Based Early Forecasting of Long‐Period Ground Motions for Large Earthquakes Along the Nankai Trough
Data Assimilation‐Based Early Forecasting of Long‐Period Ground Motions for Large Earthquakes Along the Nankai Trough
复制标题
基于资料同化的南海海槽大地震长周期地震动早期预报
DOI：
10.1029/2019jb019047
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发表时间：
2020
期刊：
影响因子：
--
通讯作者：
Maeda Takuto
中科院分区：
文献类型：
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作者：
Oba Atsuki;Furumura Takashi;Maeda Takuto
大地震引起的周期约为2-10秒的长周期地震动在沉积盆地中被强烈放大，对现代城市构成严重威胁，对摩天大楼、储油罐、大跨桥梁和其他长自然周期结构造成共振和破坏。由于LP地震动由行进距离更长且速度比体波慢得多的表面波组成，因此可以通过检测源附近强地震动的传播以及在远处盆地发生大地震动之前发出警报。在这项研究中，基于对高密度全国地震台网观测到的地震动的数据同化以及使用高分辨率地下结构模型对地震波传播的计算机模拟，提出了对LP地震动的早期预测。高速超级计算机根据当前数据同化的波场立即预测出遥远盆地中的 LP 地面运动的震动。此外，利用格林函数表示从资料同化站到预报目标站点的波传播响应，预报速度显着提高。使用 2004 年日本纪伊半岛近海地震（Mw 7.4）观测到的强震动记录以及南海海槽预期大地震场景的合成地震图进行数值测试，证明了这种基于数据同化的 LP 地震动预测与格林函数相结合的有效性。
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.