Postseismic Processes Following the 1999 Chi-Chi, Earthquake and Models of Active Crustal Deformation in Taiwan

1999 年台湾集集地震后的震后过程和活动地壳变形模型

• 批准号: 0309148
• 负责人: Paul Segall
• 金额: $ 20.31万
• 依托单位: Stanford University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-06-01 至 2006-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0309148&HistoricalAwards=false
• 关键词: Postseismic; Processes; Following; 1999; Chi

EAR-0309148SegallPostseismic Processes Following the 1999 Chi-Chi, Earthquake and Models of Active Crustal Deformation in TaiwanThe Mw = 7.5, 1999 Chi-Chi, Taiwan earthquake occurred in the center of a dense GPS network. In the first 200 days after the earthquake displacements of as much as 10 cm accumulated in both the horizontal and vertical components. The dense spatial coverage and extraordinary signal to noise ratio make the postseismic deformation field of the Chi-Chi earthquake arguably the best ever recorded. Preseismic displacement rates provide unique information on the geometry and slip-rates of active faults, the earthquake loading cycle, and tectonics of an active arc continent collision.Afterslip, viscous flow, and poroelastic relaxation have all been proposed to explain transient postseismic deformation. The data from the Chi-Chi earthquake is of such high signal to noise ratio that it is possible to discriminate between these processes. The early postseismic transient (3 months) is best explained by afterslip, however analysis of deformation over the subsequent years may reveal viscoelastic and/or poroelastic relaxation. Inversion results reveal that afterslip encircled the zone of large coseismic slip, consistent with stable slip being driven by stress changes caused by the earthquake. Inferred afterslip at seismogenic depths raises the question of why this slip occurred slowly rather than rapidly during the earthquake. Space-time inversions combined with mechanical models of slip consistent with laboratory derived friction laws will help to address this and should also elucidate fault zone properties and stresses. Inversion of both the coseismic and postseismic GPS data are consistent with a ramp-flat geometry for the Chelungpu Fault. The geometry of active faults at greater depths is, however, not fully resolved. One difficulty has been that mechanically consistent models of interseismic deformation in compressional orogenic environments are needed. We propose to develop physical 2D viscoelastic models of the earthquake cycle in Taiwan, which include the first order effects of gravity, and in which the slip rates on faults are driven by far field plate motions rather than imposed kinematically. These models, combined with the available velocity field, will allow estimates of the geometry and slip-rates on active faults in Taiwan.

EAR-0309148SEGALLPOSTESSESSEIS震动过程在1999年的Chi-Chi，地震和台湾MW = 7.5，1999 Chi-Chi，Chi-Chi，Chi-Chi，台湾地震发生后发生了主动地壳变形模型。在水平和垂直成分中，地震位移的最初200天内累积了多达10 cm。密集的空间覆盖范围和非凡的信号与噪声比使Chi-Chi地震的后视后变形场可以说是有史以来最佳记录的。 人们已经提出了有关活动断层的几何形状和滑移率，地震载荷周期以及活动弧大陆碰撞的构造的独特信息。已提出了Aftterslip，粘性流量和毛弹性松弛，以解释短暂的后震后变形。 CHI-CHI地震的数据具有如此高的信号与噪声比，因此可以区分这些过程。 后置后置瞬间最好地解释了早期的后瞬态瞬态（3个月），但是在随后几年中对变形的分析可能会揭示粘弹性和/或毛弹性弛豫。 反转结果表明，后滑动后旋转了大抗震动的区域，与地震引起的压力变化驱动的稳定滑移一致。 推断在地震深度下的后置下滑提出了一个问题，即为什么这种滑动在地震期间缓慢而不是迅速发生。 时空反转与与实验室衍生的摩擦法相一致的机械模型结合在一起，将有助于解决这一问题，还应阐明断层区的性质和应力。 Coseissic和后震后GPS数据的反转与Chelungpu断层的坡道几何形状一致。 然而，在更深入的活动断层的几何形状并未完全解决。 一个困难是，需要在压缩造山环境中机械一致的经济势变形模型。 我们建议在台湾开发地震循环的物理2D粘弹性模型，其中包括重力的一阶效应，其中断层上的滑动速率由远场板板运动驱动，而不是通过运动施加。 这些模型与可用速度场相结合，将允许在台湾活动故障上的几何和滑移率估计。