Investigating asperity activity during multiple earthquake cycles

南美洲西海岸是世界上地震最活跃的地区之一。大地震的成核和破裂扩展已被用地震异常模型概念化；这代表了俯冲板块界面上的不规则性，这些不规则性积累了弹性应变，随后破裂，产生了地震。然而，对于凸起是否代表控制断裂空间范围和前弧地震构造分割的持续地质特征，或者它们是否代表与地震间隙中积累的弹性应变释放相关的动态特征，仍然存在争议。由于俯冲地震的总震级取决于滑动量及其发生的总面积，因此确定前弧中地震隆起的位置、范围和时间演化是至关重要的。该项目的重点是在不同时间尺度上研究智利北部边缘的地震陡度；该项目将结合对隆起的更新世海洋阶地的观测，以及对地震期间和地震之间的地表位移的十年时间尺度的大地测量观测。由于地震凸起通常位于近海，无法直接检测，我提出了一种结合高分辨率测深、形态测量和数值模拟的创新方法来估计淹没海洋阶地的变形率。利用U/Th和光学激发发光方法对新出现的海洋阶地进行专门的测绘和定年，以补充这些估计。相比之下，短期变形模式和速率将通过分析GPS时间序列和已发表的震间和同震变形模型来确定。这种创新的方法将允许在不同的时间尺度上直接比较位移和变形率，并确定控制永久变形积累的潜在过程以及形成弧前区域形态的凹凸不平的作用。考虑到根据现有基础设施和人类住区评估岩石活动模式及其潜在的发震源的重要性，该项目的结果将与评估智利北部瓦尔帕莱索、伊拉佩尔和阿塔卡马地震构造段沿岸的机制、复发和可能的地震情景相关。

The West coast of South America is one of the most seismically active regions worldwide. The nucleation and rupture propagation associated with giant earthquakes has been conceptualized with the model of seismic asperities; these represent irregularities on the subducting plate interface that accumulate elastic strain and subsequently rupture generating an earthquake. However, it is still matter of debate whether asperities represent persistent geologic features that control the spatial extent of ruptures and the seismotectonic segmentation of forearcs or if they represent dynamic features related to the release of elastic strain accumulated in seismic gaps. Since the total magnitude of subduction earthquakes depends on the amount of slip and the total area over which it occurs, it is crucial to determine the location, extent, and temporal evolution of seismic asperities in forearcs. The focus of this project is the study of seismic asperities at the Northern Chile margin at different temporal scales; the project will combine observations from uplifted Pleistocene marine terraces with geodetic observations of surface displacements during and between earthquakes at decadal time scales. As seismic asperities are usually located offshore and hidden from direct inspection, I propose an innovative method combining high-resolution bathymetry, morphometry, and numerical modeling to estimate deformation rates from drowned marine terraces. These estimates will be complemented with dedicated mapping and dating of emerged marine terraces using the U/Th and optically stimulated luminescence methods. In contrast, short-term deformation patterns and rates will be determined from the analysis of GPS time series and published models of interseismic and coseismic deformation. This innovative approach will allow for a direct comparison of displacement and deformation rates at different time scales and to determine the underlying processes controlling the accumulation of permanent deformation and the role of asperities shaping the morphology of forearc regions. Considering the importance of assessing the activity patterns of asperities and their potential as seismogenic sources in light of existing infrastructure and human settlements, the results of this project will be relevant to evaluate the mechanisms, recurrence, and possible earthquake scenarios along the coast of the Valparaiso, Illapel and Atacama seismotectonic segments of Northern Chile.