The Southern Puna plateau in the central Andes has a complicated tectonic history that includes episodes of distributed shortening and extension, lithospheric delamination, uplift and Quaternary backarc volcanism. In this study, the upper crustal structure and present-day deformation in this area is investigated using a new regional earthquake catalog derived with a deep-learning-based phase picker. Results show abundant strike-slip seismicity at shallow depths in the eastern Southern Puna plateau that reveals active fault systems in the area and indicates N-S extension/E-W compression that changes orientation and relative magnitude from north to south. A broad zone of seismic quiescence in the western plateau may indicate a zone of upper crustal decoupling from large-scale deformation. The region separating the western and eastern plateau exhibits a complex stress field that can be related to the boundary of east/west oriented middle-to-lower crustal flow in the main volcanic arc. Southeast of the plateau in the Sierras Pampeanas, crustal seismicity deepens and is dominated by conjugate reverse faulting structures associated with the direction of plate convergence. Vp and Vs seismic velocity models of the upper crust obtained through local earthquake tomography with the improved seismic catalog show low-velocity anomalies near intermontane basins, except in the Antofagasta basin where a high-velocity anomaly possibly represents shallow intrusive component of Quaternary basaltic volcanism. Below the Cerro Galan caldera, an upper crustal 10-day long earthquake swarm is observed which may indicate local stress perturbations from fluids at the top of the crustal magmatic system that feeds this volcano.

中文翻译：

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南普纳高原的地震活动和当今地壳变形


安第斯山脉中部的南普纳高原具有复杂的构造历史，包括分布性缩短和伸展、岩石圈分层、隆起和第四纪后弧火山活动。在这项研究中，使用基于深度学习的相位选择器得出的新区域地震目录研究了该地区的上地壳结构和当今变形。结果显示，在南普纳高原东部的浅层深度有丰富的走滑地震活动，揭示了该地区的活跃断层系统，并表明南北向延伸/东向向压缩从北向南改变了方向和相对震级。西部高原广阔的地震静止带可能表明上地壳与大规模变形脱钩。分隔东西部高原的区域呈现出复杂的应力场，可能与主火山弧中东西向中下地壳流的边界有关。在 Sierras Pampeanas 的高原东南部，地壳地震活动加深，并以与板块辐合方向相关的共轭反向断层结构为主。通过局部地震层析成像和改进的地震目录获得的上地壳地震速度模型显示，山间盆地附近存在低速异常，但在安托法加斯塔盆地除外，那里的高速异常可能代表第四纪玄武岩火山活动的浅层侵入成分。在 Cerro Galan 破火山口下方，观察到一个长达 10 天的上地壳地震群，这可能表明为这座火山提供水源的地壳岩浆系统顶部的流体的局部应力扰动。