Collaborative Research: Utilizing GPS Measurements of Postseismic Deformation to Infer Spatial Distribution of Frictional Properties on Faults

合作研究：利用震后变形的 GPS 测量来推断断层摩擦特性的空间分布

• 批准号: 0635741
• 负责人: Kaj Johnson
• 金额: $ 9.21万
• 依托单位: Indiana University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-01-01 至 2008-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0635741&HistoricalAwards=false
• 关键词: Collaborative; Research; Utilizing; GPS; Measurements

This project is seeking to further our understanding of the distribution of frictional properties on faults by comparing afterslip models utilizing laboratory-derived rate and state friction laws with geodetic records of deformation following large earthquakes. The idealized view of fault coupling involving an interseismically locked section that ruptures in earthquakes, with aseismically creeping sections above and below the locked zone, is inconsistent with observations from a number of plate boundary faults. For example, the San Andreas fault is locked above about 15 km depth south of Parkfield, California, but north of Parkfield, the San Andreas is creeping at typically seismogenic depths. Kinematic slip inversions from the 1999 Chi-Chi, Taiwan earthquake and the 2003 Tokachi-oki, Japan earthquake show significant afterslip at typically seismogenic depths, along strike from the mainshocks. This research utilizes GPS data from these two earthquakes and the 2004 Parkfield, California earthquake to investigate the distribution of slip and frictional properties on faults. Numerical models of afterslip implementing laboratory derived rate-state friction laws are being developed and implemented in inversions of postseismic GPS time-series data for frictional parameters. The observations of aseismic slip at seismogenic depths raise important questions about frictional properties on the fault and along-strike variations of slip behavior. Faults within the seismogenic part of the crust are generally assumed to be steady-state velocity weakening. Yet, velocity weakening friction does not always lead to unstable slip and and velocity strengthening friction does not always lead to stable slip. This study investigates the conditions on the fault that allow for the spatial variations in slip behavior. High-rate GPS data recorded at 1 Hz following the Parkfield and Tokachi-oki earthquakes is being used to investigate the transition from dynamic slip during the earthquake to stable creep following the earthquake. The nature of the transition from unstable may provide further constraints on the frictional properties on the fault.

该项目正在旨在通过比较利用实验室衍生速率和国家摩擦法与大地震后变形后的地球变形记录进行比较后的摩擦模型，以进一步我们对断层上摩擦特性的分布的理解。故障耦合的理想化视图涉及地震中破裂的跨界锁定截面，而在锁定区域上方和下方的无视部分爬行的部分与许多板边界断层的观察结果不一致。例如，圣安德烈亚斯（San Andreas）断层锁定在加利福尼亚州帕克菲尔德（Parkfield）以南约15公里的深度上方，但在帕克菲尔德（Parkfield）北部，圣安德烈亚斯（San Andreas）在通常的地震深度蔓延。在1999年Chi-Chi，台湾地震和2003年Tokachi-Oki，日本地震中的运动学滑移反转在典型的地震深度上显示出明显的后滑动，并沿着主震动的罢工。这项研究利用了这两次地震中的GPS数据和2004年加利福尼亚州帕克菲尔德的地震来研究断层上的滑移和摩擦特性的分布。在摩擦参数的后震后GPS时间序列数据的倒置中，正在开发和实施实施实验室衍生速率状态摩擦法律后的后置速率状态摩擦法律的数值模型。在地震生成深度上对无性滑移的观察提出了有关摩擦特性在断层和滑移行为的局势变化上的重要问题。通常认为地壳的地震部分内的断层是稳态的速度弱化。然而，速度减弱的摩擦并不总是会导致不稳定的滑动，并且加强速度的摩擦并不总是会导致稳定的滑动。这项研究调查了断层的条件，允许滑动行为的空间变化。帕克菲尔德（Parkfield）和托卡奇（Tokachi-Oki）地震后，记录在1 Hz的高速GPS数据正在研究地震后地震期间从地震中的动态滑移到稳定蠕变的过渡。从不稳定的过渡的性质可能会对断层的摩擦特性提供进一步的限制。