High-Resolution Structure and Seismicity of the Central Chile Subduction Zone

2010年2月27日发生在智利Maule的8.8级地震被认为是1900年以来全球第六大地震。Maule地震是沿智利中部和南部汇聚板块边界发生的大型和大型俯冲逆冲地震的漫长历史中最近的一次。它在1960年智利大地震（仪器记录到的最大地震）的北部使巨型逆冲断层破裂，填补并明显延伸到已确定的地震间隙之外。智利现有的和新的本地/区域数据集提供了关键数据，使我们能够以比以前更高的精度约束该地区的边缘速度结构和地震前后的地震位置，并朝着更好地理解这个收敛的板块边界断层如何释放应变和在地震周期中演变的方向发展。需要解决的关键问题包括：(1)余震活动的上倾、下倾和沿向极限是什么？余震与前震活动和主震破裂模式的空间关系如何？(2)上下板块的结构变化是否影响主震破裂和余震分布？(3)背景地震活动性和/或余震分布中是否存在可识别的空白，这些空白可能被大地震填补？该项目包括以下步骤：首先，他们将仔细重新处理包括智利俯冲带在内的40°S至30°S区域的现有ISS、ISC和PDE数据，这些数据可以追溯到1918年，使用严格的事件质量标准，为全球数据产生显著改进的单事件震源。接下来，他们将收集所有可用的区域到达时间数据，包括来自新的和先前存在的智利、美国和国际部署的数据，然后将它们与整理好的全球数据结合起来，产生一个全面的、内部一致的边缘范围地震目录。最后，他们将使用完整的数据集进行(a)单迭代嵌套区域-全球层析成像，(b)鲁棒多迭代嵌套区域-全球层析成像，以及(c)远震双差层析成像和重新定位。该项目的目标是调查2010年2月27日智利Maule发生的8.8级地震，其余震序列以及发生地震的板块边界断层的性质。Maule地震，估计是自1900年以来全球第六大地震，是智利中部和南部汇聚板块边界的大地震历史中最近的一次。它就发生在1960年智利大地震的北部，这是有史以来仪器记录的最大地震。在这个项目中，研究人员将形成一个全面的和内部一致的地震目录进行分析。利用这些数据，研究人员将确定2010年余震序列和之前地震的精确地震位置，并绘制2010年大地震发生的板块边界区域和断层的3D结构图像。这些结果将使我们能够解决一些重要的科学问题，这些问题将帮助我们更好地理解为什么大地震会在何时何地发生。

The Mw 8.8 Maule, Chile earthquake of 27 February 2010 is estimated to be the sixth largest earthquake globally since 1900. The Maule earthquake is the most recent in a long history of large and great subduction megathrust earthquakes along the central and southern Chile convergent plate boundary. It ruptured the megathrust segment just to the north of the great 1960 Chile earthquake, the largest earthquake ever instrumentally recorded, filling in and apparently extending beyond an identified seismic gap. Existing and new local/regional datasets for Chile provide key data allowing us to constrain marginwide velocity structure and pre- and post-seismic earthquake locations with a greater accuracy than has been achieved before for this region and move toward a better understanding of how this convergent plate boundary fault releases strain and evolves over the seismic cycle. Among the key issues to be addressed are the following: (1) What are the updip, downdip, and along-strike limits of aftershockactivity, and how do aftershocks spatially relate to prior seismicity and main shock rupture pattern? (2) Do structural variations in the upper and lower plates affect main shock rupture and aftershock distribution? (3) Are there identifiable gaps in the background seismicity and/or aftershock distribution that could be potentially filled by a major earthquake? The project involves the following steps: First, they will carefully reprocess the available ISS, ISC, and PDE data for the region encompassing the Chile subduction zone from about 40° S to 30° S, extending as far back in time as 1918, using stringent event quality criteria to produce significantly improved single event hypocenters for the global data. Next, they will gather all available regional arrival time data, including data from new and preexisting Chilean, U.S. and international deployments, and then combine them with the groomed global data to produce a comprehensive and internally consistent margin-wide earthquake catalog. Finally, they will use the complete dataset for (a) single-iteration nested regional-global tomography, (b) robust multiple-iteration nested regional-global tomography, and (c) teleseismic double-difference tomography and relocation.The goal of this project is to investigate the Mw 8.8 Maule, Chile earthquake of 27 February 2010, its aftershock sequence, and the nature of the plate boundary fault on which it occurred. The Maule earthquake, estimated to be the sixth largest earthquake globally since 1900, is the most recent in a long history of large and great earthquakes along the central and southern Chile convergent plate boundary. It occurred just to the north of the great 1960 Chile earthquake, the largest earthquake ever instrumentally recorded. In this project, researchers will form a comprehensive and internally consistent catalog of earthquakes for analysis. Using these data, researchers will determine precise earthquake locations for the 2010 aftershock sequence and prior earthquakes and image the 3D structure of the plate boundary region and the fault on which the 2010 great earthquake occurred. These results will allow us to address significant scientific questions that will help us better understand why great earthquakes occur where they do, when they do.