Quantifying rupture characteristics of microearthquakes in the Parkfield Area using a high-resolution borehole network
Quantifying rupture characteristics of microearthquakes in the Parkfield Area using a high-resolution borehole network
复制标题
使用高分辨率钻孔网络量化帕克菲尔德地区微地震的破裂特征
DOI：
10.1093/gji/ggad023
复制
发表时间：
2023
影响因子：
2.8
通讯作者：
Abercrombie, Rachel E.
中科院分区：
文献类型：
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作者：
Pennington, Colin N.;Wu, Qimin;Chen, Xiaowei;Abercrombie, Rachel E.
众所周知，大地震往往表现出显著的破裂复杂性，如分离良好的子事件。随着记录和数据处理技术的改进，人们发现小地震也表现出破裂的复杂性。研究这些小地震提供了更好地了解破裂复杂性的可能原因的机会。特别是，如果它们是随机的或与故障属性有关。我们检查微震（M< 3）在帕克菲尔德，加州，该地区记录的高分辨率钻孔网络。我们量化地震的复杂性，从简单的圆形（Ω-平方）源模型的源时间函数和源谱的偏差。我们建立阈值来宣布复杂性，并发现它可以在大于2级的地震中检测到，最好的分辨率高于M2.5。两种方法之间的比较显示出良好的一致性（> 90%），这意味着两种方法都表征了相同的源复杂性。对于这两种方法，60- 80%（M2.6-3）的已解决事件都很复杂，具体取决于方法。我们观察到的复杂事件往往聚集在以前确定的结构复杂性的地区;在2004年帕克菲尔德Mw 6地震后的几天里，大部分地震表现出复杂性。忽略这些小事件的复杂性可能会引入伪影或增加应力降测量的不确定性。然而，仅关注简单事件可能导致系统性偏差、缩放伪像以及缺乏对结构复杂区域的应力测量。
It is well known that large earthquakes often exhibit significant rupture complexity such as well separated subevents. With improved recording and data processing techniques, small earthquakes have been found to exhibit rupture complexity as well. Studying these small earthquakes offers the opportunity to better understand the possible causes of rupture complexities. Specifically, if they are random or are related to fault properties. We examine microearthquakes (M< 3) in the Parkfield, California, area that are recorded by a high-resolution borehole network. We quantify earthquake complexity by the deviation of source time functions and source spectra from simple circular (omega-square) source models. We establish thresholds to declare complexity, and find that it can be detected in earthquakes larger than magnitude 2, with the best resolution above M2.5. Comparison between the two approaches reveals good agreement (>90 per cent), implying both methods are characterizing the same source complexity. For the two methods, 60–80 per cent (M2.6–3) of the resolved events are complex depending on the method. The complex events we observe tend to cluster in areas of previously identified structural complexity; a larger fraction of the earthquakes exhibit complexity in the days following theMw6 2004 Parkfield earthquake. Ignoring the complexity of these small events can introduce artefacts or add uncertainty to stress drop measurements. Focusing only on simple events however could lead to systematic bias, scaling artefacts and the lack of measurements of stress in structurally complex regions.