The Significance of Long‐Period Ground Motion at Regional to Teleseismic Distances From the 610‐km Deep Mw 8.3 Sea of Okhotsk Earthquake of 24 May 2013
The Significance of Long‐Period Ground Motion at Regional to Teleseismic Distances From the 610‐km Deep Mw 8.3 Sea of Okhotsk Earthquake of 24 May 2013
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DOI：
10.1029/2019jb018147
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发表时间：
2019-08
期刊：
影响因子：
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通讯作者：
T. Furumura;B. Kennett
中科院分区：
文献类型：
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作者：
T. Furumura;B. Kennett
2013年5月24日发生在鄂霍次克海下(610公里，8.3兆瓦)的地震在整个日本岛屿上产生了显著的地面运动，震中距离从1300公里到4200公里。最大地震集中在俯冲带弧后一侧，这与太平洋板块深部地震的正常模式相反。对日本各地密集的Hi-Net和F-Net台阵的观测表明，日本北部(震中距离近2,000公里)的最大震动是由近焦散的S波引起的，来自深源的上行和下行波以及来自660公里不连续面的反射波三倍增长。三维有限差分方法模拟证实，高波速板的反波导效应是将强度较大的区域向南推进了300公里，比预期的要远。板变形后的S波前在自由面上发生近临界入射，产生大SP，并产生具有S周期的剪切耦合PL(S-PL)波。随着震中距的增加，S入射角超过临界，SS全反射与SSS在很大距离(>；3000公里)甚至更远(>；6000公里)处产生大的地面运动。在地壳较厚的大陆构造中，SS、与SS-PL相连的SSS和SSS-PL波列的传播是非常有效的。在距离2013年鄂霍次克海大地震(4,000-8,000公里)的地方，FET报告可以用大陆环境中长时间的长周期地面运动来解释，沉积盆地和高层建筑中的地面运动被放大了。
The 24 May 2013 earthquake beneath the Sea of Okhotsk (610 km, Mw 8.3) produced significant ground motion across the whole span of the Japanese islands, from 1,300‐ to 4,200‐km epicentral distance. The largest shaking was concentrated along the back‐arc side of the subduction zone, which is the opposite of the normal pattern for deep earthquakes in the Pacific slab. Observations from the dense Hi‐net and F‐net arrays across Japan show that the largest shaking in northern Japan (near 2,000‐km epicentral distance) was caused by near‐caustic S waves, with triplication of upgoing and downgoing waves from the deep source and reflected waves from the 660‐km discontinuity. Three‐dimensional finite difference method simulations confirm that the antiwaveguide effect of the high‐wave speed slab is to push the zone of larger intensity 300 km farther to south than might be expected. The S wavefront distorted by the slab has near‐critical incidence at the free surface producing large sP and generating shear‐coupled PL (s‐PL) waves with period >3 s. With increasing epicentral distance the S incident angle exceeds critical, then total sS reflection creates large ground motion at large distance (>3,000 km) and even farther (>6,000 km) with sSS. The propagation of sS, sSS linking to sS‐PL, and sSS‐PL wave trains is very efficient in continental structures with thicker crust. The felt reports at large (4,000–8000 km) distances from the 2013 Sea of Okhotsk earthquake can be explained by lengthy, long‐period ground motion in the continental environment with amplification in sedimentary basins and in tall buildings.