Detection Limits and Near‐Field Ground Motions of Fast and Slow Earthquakes
Detection Limits and Near‐Field Ground Motions of Fast and Slow Earthquakes
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DOI：
10.1029/2019jb018935
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发表时间：
2020-07
期刊：
影响因子：
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通讯作者：
G. Kwiatek;Y. Ben‐Zion
中科院分区：
文献类型：
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作者：
G. Kwiatek;Y. Ben‐Zion
我们调查的理论极限检测的快速和缓慢的地震事件，预计从M6地震在短震中距离的地面运动的空间变化。这些分析是基于用离散波数方法计算的合成速度地震图，假定南加州地壳的地震速度和衰减特性。所检查的震源特性包括不同的震级（M −1.0至M 6.0）、静态应力降（0.1-10 MPa）以及慢破裂和快破裂（剪切波速为0.1-0.9）。对于M6事件，我们还考虑了产生裂纹和脉冲型事件的上升时间的变化以及不同的破裂方向性。慢地震所产生的地面运动幅度比相同震级的常规快地震要低得多，因此更难检测。静态应力降和滑动上升时间也影响最大辐射地震运动，因此事件的可检测性。除了几何因素外，短震中距地震地面运动的饱和和衰减还与辐射图、地震规模（震级、应力降）和破裂方向性有关。破裂速度、上升时间和方向性对地震动的空间分布有显著影响。研究结果有助于优化慢速和快速小震的检测，并有助于了解大震引起的地面运动的空间分布。
We investigate theoretical limits to detection of fast and slow seismic events, and spatial variations of ground motion expected from M 6 earthquakes at short epicentral distances. The analyses are based on synthetic velocity seismograms calculated with the discrete wavenumber method assuming seismic velocities and attenuation properties of the crust in Southern California. The examined source properties include different magnitudes (M −1.0 to M 6.0), static stress drops (0.1–10 MPa), and slow and fast ruptures (0.1–0.9 of shear wave velocity). For the M 6 events we also consider variations in rise times producing crack‐ and pulse‐type events and different rupture directivities. Slow events produce ground motion with considerably lower amplitude than corresponding regular fast earthquakes with the same magnitude, and hence are significantly more difficult to detect. The static stress drop and slip rise time also affect the maximum radiated seismic motion, and hence event detectability. Apart from geometrical factors, the saturation and depletion of seismic ground motion at short epicentral distances stem from radiation pattern, earthquake size (magnitude, stress drop), and rupture directivity. The rupture velocity, rise time, and directivity affect significantly the spatial pattern of the ground motions. The results can help optimizing detection of slow and fast small earthquakes and understand the spatial distribution of ground motion generated by large events.