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。与大地震相关的形核和破裂传播已用地震凹凸体模型概念化；这些凹凸体代表俯冲板块界面上的不规则，积累弹性应变，随后破裂产生地震。然而，凹凸体是代表了控制破裂空间范围和前弧地震构造分段的持久地质特征，还是代表了与释放地震空区中积累的弹性应变有关的动态特征，仍是一个有争议的问题。由于俯冲地震的总震级取决于滑移量和发生俯冲地震的总面积，因此确定前弧区地震凹凸体的位置、范围和时间演化是至关重要的。该项目的重点是研究智利北部边缘不同时间尺度上的地震凹凸体；该项目将结合从升起的更新世海洋阶地进行的观测，以及在十年时间尺度上对地震期间和两次地震之间地面位移的大地测量。由于地震凹凸体通常位于近海，无法直接观测，我提出了一种结合高分辨率水深测量、形态测量和数值模拟的新方法来估计溺水海洋阶地的形变速率。这些估计将与使用U/Th和光学刺激发光方法对出现的海洋阶地进行专门的测绘和测年相补充。相反，短期形变模式和速率将通过分析GPS时间序列和公布的震间和同震形变模型来确定。这一创新办法将使人们能够直接比较不同时间尺度上的位移和形变率，并确定控制永久变形累积的基本过程和塑造弧前区域形态的凹凸体的作用。考虑到根据现有基础设施和人类住区评估凹凸体的活动模式及其作为孕震源的潜力的重要性，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海的机制、复发和可能的地震情景有关。

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.