Exploring Deep Fault Mechanics by Identifying Non-Volcanic Tremor on Southern California Faults

通过识别南加州断层上的非火山震颤探索深层断层力学

• 批准号: 0943892
• 负责人: David Oglesby
• 金额: $ 16万
• 依托单位: University of California-Riverside
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-02-01 至 2014-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0943892&HistoricalAwards=false
• 关键词: Exploring; Deep; Fault; Mechanics; Identifying

The investigator will undertake a study of non-volcanic tremor in southern California using continuous seismic data made available by the Southern California Seismic Network (SCSN). Initially, they will focus our search for tremor near Anza, California in a densely instrumented region of southern California that has both surface and borehole continuous seismic data. These high-quality data will be used to determine the frequency content and duration of tremor that occurs near Anza allowing for tuning of future searches to these features. An automatic tremor detection scheme will then be used to search for tremor across all SCSN stations over a 5-year time period. These efforts provide the foundation to address fundamental questions about physical conditions necessary for non-volcanic tremor in California. They will also determine whether tremor is correlated with local earthquakes, teleseismic wave arrivals, Earth tides, or observations of slow slip or aseismic creep. And, they will determine whether tremor occurrence correlates with known fault geometries or material properties. The major questions to be addressed in this proposal are: 1) Does tremor occur primarily along well-developed, through-going faults such as the San Andreas or San Jacinto fault zones?; 2) Does non-subduction zone tremor occur primarily in regions of a fault that are likely to be in conditionally stable such as: a) at depths less than 5 km in shallow sediments and/or b) deep (15 -20 km) on crustal faults beneath the seismogenic zone?, and 3) Is timing of tremor in California controlled by stressing events such as the passage of teleseismic waves, changes in local seismicity rates, or tidal forces? If so, what is the stress amplitude and period required to trigger tremor?Tremor are low amplitude, long duration seismic signals that have been only recently discovered in seismic data recorded continuously. The first observations of tremor were made in Japan and found to occur deep on the subducting plate interface. Tremor has since been observed at multiple plate boundaries around the globe, most recently along several faults in California. Tremor typically occurs deep on faults, below the portion of the crust that ruptures during an earthquake. It turns out that tremor is part of a suite of seismic and geodetic phenomena likely associated with deep slip on faults. By studying the details of tremor occurrence, including when and where tremor is typically observed, under what conditions tremor can be triggered, and the relationship between tremor and regular earthquakes, we can investigate the frictional properties of faults to greater depths than was previously possible using seismic data.

研究人员将使用南加州地震网络（SCSN）提供的连续地震数据对南加州进行非volcanic震颤的研究。最初，他们将集中在加利福尼亚州安扎附近的震颤中，在南加州的一个密集的仪器区域，该地区具有表面和井眼连续的地震数据。这些高质量的数据将用于确定ANZA附近发生的频率内容和持续时间，以便将未来的搜索调整为这些功能。然后，将使用自动震颤检测方案在5年的时间内搜索所有SCSN站的震颤。这些努力为解决加利福尼亚州非沃尔卡尼克震颤所必需的身体状况的基本问题奠定了基础。他们还将确定震颤是与局部地震，远程震荡的到达，潮汐或慢速滑移或无自然蠕变的观察相关的。而且，他们将确定震颤的发生是否与已知的断层几何形状或材料特性相关。该提案中要解决的主要问题是：1）震颤主要发生在发达的，贯穿的断层，例如San Andreas或San Jacinto断层区？ 2）非分支区域震颤是否主要发生在有条件稳定的断层区域中，例如：a）在浅层沉积物和/或b）在浅层沉积物中和/或b）深处（15 -20 km）在地壳区域下的地壳上的深处（15 -20 km）处于地震区域下方？费率还是潮汐力？如果是这样，触发震颤所需的应力振幅和周期是什么？震颤是低振幅，持续持续时间的地震信号，直到最近才在连续记录的地震数据中发现。震颤的第一个观察结果是在日本进行的，并发现在俯冲板界面深处。此后，在全球多个板块边界上观察到了震颤，最近一次是沿加利福尼亚的几个断层。震颤通常在地震期间破裂的地壳部分下方的断层深处发生。事实证明，震颤是一系列地震和大地测量现象的一部分，可能与深层滑倒有关。通过研究震颤发生的细节，包括通常观察到震颤的何时何地，在哪种条件下可以触发震颤以及震颤与常规地震之间的关系，我们可以研究断层的摩擦特性到以前可能更大的深度，而不是使用地震数据。