Rupture Directivity of the 2021 ML 2.2 Gwangyang, Korea, Microearthquake: Toward Resolving High-Resolution Rupture Process of a Small Earthquake
Rupture Directivity of the 2021 ML 2.2 Gwangyang, Korea, Microearthquake: Toward Resolving High-Resolution Rupture Process of a Small Earthquake
复制标题
2021 ML 2.2 韩国光阳微地震的破裂方向性：致力于解决小地震的高分辨率破裂过程
DOI：
10.1785/0320220030
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发表时间：
2022
期刊：
影响因子：
--
通讯作者：
Younghee Kim
中科院分区：
文献类型：
--
作者：
Minyoung Seo;Won;Younghee Kim
中~大地震（m>.6）常表现出明显的破裂指向性。最近的研究表明，由于加强了地震监测，相当大比例的小地震（M< ~ 5）也显示出破裂指向性。破裂指向性是所有大小地震的共同特征吗？在这项研究中，我们利用最近扩大的密集地震台网的数据，研究了2021年8月27日发生在朝鲜半岛南端的ML 2.2光阳微地震的破裂方向性。主震有两次前震和三次余震，这使我们能够根据精确的相对事件位置和良好的震源机制来定义断层面。利用经验格林函数技术对视源时间函数进行分析，发现主震是单向向东破裂的。对源脉冲离开震源球的三维详细分析表明，破裂方向与断层几何形状和滑动方向一致。我们的研究表明，在足够的方位角覆盖范围内，我们可以解决单侧破裂微地震（M< ~ 3）的破裂方向性问题，这将有助于我们更好地了解全球低地震活动性地区的孕震过程。
Moderate-to-large earthquakes (M>6) frequently show clear rupture directivity. Recent studies revealed that a substantial percentage of small-sized earthquakes (M<∼5) display rupture directivity as well, owing to enhanced seismic monitoring. Is rupture directivity a common feature for earthquakes of all sizes? In this study, we investigated the rupture directivity of the 27 August 2021 ML 2.2 Gwangyang microearthquake that occurred at the southern tip of the Korean Peninsula by utilizing data from a recently expanded dense seismic network. The mainshock had two foreshocks and three aftershocks, which enabled us to define the fault plane from precise relative event locations and a well-constrained focal mechanism. Analysis of apparent source time functions obtained with the empirical Green’s function technique reveals that the mainshock ruptured unilaterally toward the east. A detailed analysis of the source pulse leaving the focal sphere in 3D indicates that rupture directivity is consistent with the fault geometry and slip direction. Our study demonstrates that we can resolve rupture directivity of unilaterally rupturing microearthquakes (M<∼3) given adequate azimuthal coverage, and that this will lead to an improved understanding of the seismogenic processes in regions of low seismicity worldwide.