Disentangling roles of stress, pore pressure and shaking from wavefields recorded during the 2014 Northern Chile earthquake sequence

尽管我们对产生大地震的宏观环境有了大致的了解，但导致地震破裂的物质内部过程存在着重大的不确定性。然而，这些局部过程是控制断裂演变成大地震的关键组成部分。智利北部的地震序列在2014年4月1日的伊基克地震（Mw 8.1）中达到高潮，由于其延伸的前震序列与主震一起被智利综合板块边界观测站（IPOC）捕获，因此为研究俯冲带中的这种变形和破坏过程提供了一个特殊的机会。在大地震的准备阶段监测到大量的地震活动本身就很有趣，因为它为研究即将发生的大地震的准备阶段提供了一个独特的机会。此外，由于前震和余震序列部分重叠，断裂带在地震前后以类似的方式被照亮，从而简化了对静态结构及其变异性的研究。这种可能性是缺乏在大多数序列先前的研究与本文提出的方法。为了约束伊基克地震序列中影响地震发生的主要因素，我们在三个方向(A)高精度地震活动性测绘，(B)层析结构成像和(C)时间物质变化检测中使用了地震干涉测量和波形处理。联合分析将根据应力、孔隙压力变化和震动影响来解释结果。高精度的基于波形的事件重新定位将描绘活动区域并识别重复事件的集群，以便了解异常的分布及其随时间的可能变化。波形分析将用于更好地约束主要发生在近海的地震活动的深度，这对于理解上覆板块、板块界面和下行板块之间的变形划分至关重要。此外，重复事件的目录构成了尾波干涉测量和确定双差S - P旅行时间的时间依赖性的基础。最后，环境噪声干涉测量法将用于从表面波层析成像推断静态剪切速度结构，以及推断随时间的变化。该项目是一个研究联盟的一部分，整个项目的基本原理在本申请附件的摘要文件中提供。

Despite our general understanding of the macroscopic circumstances that generate large earthquakes, significant uncertainties exist about the internal processes in the material that hosts the rupture. However, these local processes are the crucial component that govern the evolution of a rupture into a large earthquake.The earthquake sequence in northern Chile that culminated in the April 1st 2014 Iquique earthquake (Mw 8.1) represents an exceptional opportunity for the investigation of such deformation and damage processes in a subduction zone because of its extended foreshock sequence, which was captured alongside the main shock by the Integrated Plate boundary Observatory of Chile (IPOC). Well monitored plentiful seismicity in the preparation phase of the large event is interesting in itself as it provides a unique opportunity to study the preparatory phase of an imminent great earthquake. In addition, as the foreshock and aftershock sequences partially overlap, the fault zone is illuminated in a similar way before and after the earthquake, easing both the study of the static structure as well as its variability. Such a possibility is lacking in most of the sequences previously investigated with the methods proposed here.To constrain the dominant factors influencing seismogenesis during the Iquique earthquake sequence we use seismic interferometry and waveform processing in three directions: (A) high precision seismicity mapping, (B) tomographic structural imaging, and (C) detection of temporal material changes. A joint analysis will interpret the results in terms of stress, pore pressure variations and impact of shaking. High precision waveform-based event relocation will delineate areas of activity and identify clusters of repeating events in order to understand the distribution of asperities and their possible variability through time. Waveform analysis will be used to better constrain the depth of the predominantly offshore seismicity, crucial for understanding the partition of deformation between the overriding plate, the plate interface and the downgoing plate. Also, a catalogue of repeating events forms the basis for the application of coda wave interferometry and determination of time-dependencies in double-difference S minus P travel times. Finally, ambient noise interferometry will be used to infer the static shear velocity structure from surface wave tomography but also to infer time-dependent changes.This project is part of a research consortium and a rationale for the whole project bundle is provided in a summary paper attached to this application.