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普遍的了解，但对于承载破裂的物质的内部过程仍存在重大的不确定性。然而，这些局部过程是控制破裂演化为大地震的关键组成部分。智利北部的地震序列最终在2014年4月1日的伊基克地震(Mw 8.1)中达到顶峰，由于其延长的前震序列，智利综合板块边界观测站(IPOC)与主震一起捕捉到的前震序列，为研究俯冲带的这种变形和破坏过程提供了一个难得的机会。在大地震准备阶段得到充分监测的丰富地震活动本身就很有趣，因为它为研究即将到来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，断层带在地震前后以类似的方式照亮，这使得对静态结构及其变异性的研究变得容易。为了约束在伊基克地震序列中影响地震孕育的主导因素，我们从三个方向使用了地震干涉测量和波形处理：(A)高精度地震活动填图，(B)层析构造成像，(C)时间材料变化检测。联合分析将从应力、孔压变化和震动的影响方面解释结果。基于波形的高精度事件重新定位将划定活动区域并识别重复事件的集群，以便了解凹凸体的分布及其随时间的可能变化。波形分析将被用来更好地约束以近海为主的地震活动的深度，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应用尾波干涉测量和确定S双差减去P旅行时的时间相关性的基础。最后，环境噪声干涉测量法将用于从面波层析成像中推断静态剪切速度结构，还将用于推断随时间变化的变化。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所附的总结论文中提供。

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.