Midcrustal moderate-size earthquake occurrence in paleovolcanic structures off Jeju Island, South Korea

IF 2.4 3区 地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS
Junhyung Lee, Tae-Kyung Hong, Seongjun Park, Byeongwoo Kim
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引用次数: 0

Abstract

A series of midcrustal moderate-size earthquakes occurred in the Korean Peninsula recently. A midcrustal ML4.9 strike-slip earthquake with a fault-plane strike in N-S occurred on December 14, 2021 at the southwestern offshore region of Jeju Island, South Korea. The fault plane orientation and slip sense (faulting mechanism) hardly conform with the regional stress field. The deep focal depth and N-S directional strike-slip motion require transient changes in the medium properties and stress field. Strong ground motions of the midcrustal earthquake induce preferential dynamic stress changes in NE-SW direction, triggering subsequent aftershocks in NE-SW-directional adjacent faults. Both the static and dynamic stress changes caused by the mainshock contribute to the aftershock sequence. The number and focal depths of aftershocks decrease with distance from the mainshock. The different fault-plane orientations between the mainshock and aftershocks suggest earthquake nucleations in independent fault structures. The mainshock occurred in aseismic midcrustal paleovolcanic structure on the outskirt of a high seismicity region. The ML4.9 earthquake suggests possible nucleation of earthquake in seismically-inactive paleotectonic structures, successively incurring aftershocks conforming to the ambient stress. The mainshock and aftershocks suggest that paleotectonic structures may behave as source structures to spawn earthquakes.

韩国济州岛附近古火山结构中的中地壳中等规模地震发生情况
朝鲜半岛近期发生了一系列中地壳中等规模地震。2021 年 12 月 14 日,韩国济州岛西南近海地区发生了一次中地壳 ML4.9 走向滑动地震,断层面走向为 N-S。断层面走向和滑移感(断层机制)与区域应力场几乎不一致。深层病灶和 N-S 向走向滑动运动要求介质性质和应力场发生瞬时变化。地壳中层地震的强烈地动引起东北-西南方向的优先动应力变化,引发东北-西南方向邻近断层的后续余震。主震引起的静应力和动应力变化都对余震序列产生了影响。余震的次数和震源深度随着与主震距离的增加而减小。主震和余震的断层面方向不同,表明地震成核是在独立的断层结构中发生的。主震发生在高震区外围的无震中壳古火山构造中。ML4.9 地震表明,在地震不活跃的古构造中可能出现地震核,并相继发生符合环境应力的余震。主震和余震表明,古构造可能是引发地震的震源结构。
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来源期刊
Physics of the Earth and Planetary Interiors
Physics of the Earth and Planetary Interiors 地学天文-地球化学与地球物理
CiteScore
5.00
自引率
4.30%
发文量
78
审稿时长
18.5 weeks
期刊介绍: Launched in 1968 to fill the need for an international journal in the field of planetary physics, geodesy and geophysics, Physics of the Earth and Planetary Interiors has now grown to become important reading matter for all geophysicists. It is the only journal to be entirely devoted to the physical and chemical processes of planetary interiors. Original research papers, review articles, short communications and book reviews are all published on a regular basis; and from time to time special issues of the journal are devoted to the publication of the proceedings of symposia and congresses which the editors feel will be of particular interest to the reader.
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