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.

该项目旨在通过将利用实验室推导的速率和状态摩擦定律的后滑模型与大地震后变形的大地测量记录进行比较，进一步了解断层上摩擦特性的分布。断层耦合的理想化观点涉及在地震中破裂的震间锁定部分，以及锁定区上方和下方的抗震蠕动部分，这与许多板块边界断层的观测结果不一致。例如，圣安德烈亚斯断层被锁定在加利福尼亚州帕克菲尔德以南约 15 公里深度以上，但在帕克菲尔德以北，圣安德烈亚斯断层正在典型的地震深度蠕动。 1999 年台湾集集地震和 2003 年日本十胜冲地震的运动滑移反演显示，沿着主震的走向，在典型的震源深度处存在显着的后滑。这项研究利用这两次地震和 2004 年加利福尼亚州帕克菲尔德地震的 GPS 数据来调查断层上滑移和摩擦特性的分布。正在开发采用实验室导出的速率状态摩擦定律的后滑数值模型，并在震后​​ GPS 时间序列数据的摩擦参数反演中实施。对地震发生深度的地震滑移的观测提出了有关断层摩擦特性和滑移行为沿走向变化的重要问题。地壳发震部分内的断层通常被认为是稳态速度减弱。然而，速度减弱的摩擦并不总是导致不稳定的滑移，并且速度增强的摩擦并不总是导致稳定的滑移。这项研究调查了断层上允许滑动行为发生空间变化的条件。 Parkfield 和 Tokachi-oki 地震后以 1 Hz 记录的高速 GPS 数据被用来研究从地震期间的动态滑移到地震后稳定蠕变的转变。从不稳定转变的性质可能对断层上的摩擦特性提供进一步的限制。