Investigations of Spatial and Temporal Variations in Strain Accumulation at the Sumatra Subduction Zone from Continuous GPS Measurements

Bock 0001090苏门答腊岛西海岸和明打威群岛提供了一个独特的机会来研究应变积累和释放的过程，沿着苏门答腊断层和俯冲带。两次巨大的历史地震（1833年和1861年）表明，罕见的特大地震主导了苏门答腊俯冲带的应变释放。苏门答腊断层也被认为产生了几次Mw 7地震。从1989年到1993年收集的GPS测量揭示了地表形变的空间分布，这表明俯冲界面沿着1833年大地震的震源区完全锁定，但仅沿着1861年事件的震源区部分锁定。这些数据还导致了对Summandra断层几个部分的滑动率估计。调查人员计划在苏门答腊岛和明打威群岛上大约50个已建立的GPS纪念碑上进行纪念碑式的调查。这些站点的新测量结果将结合其早期数据进行分析，以获得苏门答腊前弧和苏门答腊断层一段的最新时均速度场。通过这种分析，他们希望解决两个关于苏美尔断层和俯冲带的重要问题。首先，他们希望确定1989-1994年测量所观察到的苏美尔俯冲带的应变分段是否是一个长期信号，或者它是否是由例如地震滑动事件引起的瞬时效应。他们希望解决的第二个问题是位于大约1 S的Summandra断层段的滑动速率。他们目前估计的滑动率为235毫米/年，大大高于从河流偏移估计的11毫米/年。这是UCSD的斯克里普斯海洋学研究所（SIO）和印度尼西亚国家测绘协调机构（BAKOSURTANAL）之间的合作提案。

Bock 0001090 The west coast of Sumatra and the Mentawai Islands offer a unique opportunity to study the process of strain accumulation and release along the Sumatran fault and subduction zone. Two giant historical earthquakes (1833 and 1861) suggest that infrequent very-large earthquakes dominate strain relief at the Sumatra subduction zone. The Sumatran fault has also been known to produce several Mw7 earthquakes. GPS measurements collected from 1989 to 1993 revealed the spatial distribution of surface deformation, suggesting that the subduction interface is completely locked along the source region of the 1833 giant earthquake, but is only partially locked along the source region of the 1861 event. The data have also resulted in slip rate estimates for several segments of the Sumatran fault. The investigators plan to conduct campaign-style surveys at approximately fifty of their established GPS monuments on Sumatra and the Mentawai islands. The new measurements from these sites will be analyzed in conjunction with their earlier data to obtain an updated, time-averaged velocity field for the Sumatra forearc and one segment of the Sumatran fault. With this analysis they hope to resolve two important questions about the Sumatran fault and subduction zone. First, they hope to determine whether the strain segmentation of the Sumatran subduction zone observed by the 1989-1994 measurements is a long-term signal, or if it was a transient effect caused by, for example, an aseismic slip event. The second question they hope to resolve is the slip rate for the Sumatran fault segment located about 1 S. Their current estimate of the slip rate there is 235 mm/yr, considerably larger than the 11 mm/yr estimated from stream offsets. This is a collaborative proposal between UCSD's Scripps Institution of Oceanography (SIO) and the Indonesian National Coordination Agency for Surveying and Mapping (BAKOSURTANAL).