Investigations of the 2004 Parkfield Earthquake Sequence

2004 年帕克菲尔德地震序列的调查

• 批准号: 0510108
• 负责人: Douglas Dreger
• 金额: $ 14.4万
• 依托单位: University of California-Berkeley
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-07-01 至 2007-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0510108&HistoricalAwards=false
• 关键词: Investigations; 2004; Parkfield; Earthquake; Sequence

The Parkfield segment of the San Andreas fault has been intensively monitored with a broad array of geophysical instrumentation in anticipation of recording the next in a series of earthquakes that repeat on average approximately every 22 years. Although the official prediction for the occurrence of the event in 1988 +- 5 years (Bakun and Lindh, 1985) failed, fortunately the monitoring efforts continued. On September 28, 2004 a magnitude 6 earthquake occurred, and it has produced a wealth of new data to study the mechanics of the faulting process both coseismically (at the time of the mainshock) and postseismically. The 2004 Parkfield earthquake is arguably the best recorded to date with observations of near-fault strong ground motion, continuous GPS, surface creep, borehole strain, ground water and EM signals, as well as regional broadband waveform data. In the proposed research a high-resolution model of the rupture process, namely the distribution of fault slip in both space and time will be determined from local and more distant seismic instruments as well as surface deformation obtained from GPS. Additionally a postseismic slip model will be obtained from the continuous GPS data. These high-resolution models will then be used to calculate the stress change on the fault and relate it to the behavior of aftershocks, characteristically repeating earthquakes (whose behavior was changed by the occurrence of the mainshock), and postseismic slip giving insight into the fault zone rheology. Regional and teleseismic records of the previous Parkfield earthquakes in 1922, 1934, and 1966 are available and will be compared with similar records for the 2004 event to evaluate the characteristic earthquake hypothesis for large events in the region. This project will address fundamental questions about the relationships between mainshocks, aftershocks, pre-event seismicity, and post-seismic deformation. It will also address the question of source parameter resolution of fault slip inversions with the goal of better understanding underlying rupture dynamics and the earthquake hazard application of near-realtime ground motion reporting.

圣安地列斯断层的帕克菲尔德部分已经被广泛的地球物理仪器集中监测，预计将记录下平均每22年重复一次的一系列地震中的下一次地震。虽然官方对1988 + 5年（Bakun and Lindh, 1985）事件发生的预测失败，但幸运的是，监测工作仍在继续。2004年9月28日发生了一场6级地震，它为研究断层过程的同震（主震发生时）和震后机制提供了丰富的新数据。2004年帕克菲尔德地震可以说是迄今为止记录最好的近断层强地面运动、连续GPS、地表蠕变、钻孔应变、地下水和电磁信号以及区域宽带波形数据。在本研究中，将通过本地和更远的地震仪器以及GPS获得的地表变形来确定断裂过程的高分辨率模型，即断层滑动在空间和时间上的分布。此外，利用连续的GPS数据得到地震后滑动模型。然后，这些高分辨率模型将用于计算断层上的应力变化，并将其与余震的行为联系起来，余震的特征是重复地震（其行为因主震的发生而改变），以及震后滑动，从而深入了解断裂带的流变学。帕克菲尔德以前的1922年、1934年和1966年地震的区域和远震记录是可用的，并将与2004年地震的类似记录进行比较，以评估该地区大地震的特征地震假设。该项目将解决有关主震、余震、震前地震活动和震后变形之间关系的基本问题。它还将解决断层滑动反演的源参数解析问题，目的是更好地理解潜在的破裂动力学和近实时地震动报告的地震危险性应用。