This paper aims to better comprehend the crustal structure of the Precordillera and the Iglesia Valley. Located in the northern sector of the Pampean flat-slab (San Juan, Argentina), this region was the epicenter of the historical 1894, M > 7 earthquake (intensity IX on the modified Mercalli scale) and thus considered as a region of particularly high seismic hazard. The structure and deformation style associated with such events remain poorly understood.

In this study, we analyze 4 months of regional seismic records from national and international stations in order to characterize a sequence of 74 crustal events that followed the occurrence of an intermediate magnitude (M_W = 4.8 and M_L = 5.2) earthquake on October 28th, 2019 for which we constrain the source parameters using regional moment tensor inversion.

The analysis also includes the determination of 11 focal mechanisms from P-wave polarities and P–S waves amplitude ratios. Most of the focal mechanisms indicate reverse motion solutions.

Seismological results are then integrated with other geophysics (gravity and seismic reflection profiles) as well as geological data, to build a 3D structural model that allows a better understanding of the crustal deformation mechanisms of the study area.

Our results suggest that the seismic deformation is mostly concentrated in the basement of the Western Precordillera, at the transition with the Frontal Cordillera. This deformation seems respond to compressional stresses. The proposed model provides evidence of ongoing seismic activity related to the interaction between the thick-skinned deformation of the Frontal Cordillera with the thin-skinned fold and thrust belt of the Western Precordillera.

本文旨在更好地理解Precordillera和Iglesia山谷的地壳结构。该地区位于 Pampean 平板（阿根廷圣胡安）的北部，是 1894 年历史上 M > 7 地震（修正 Mercalli 震级的 IX 级）的震中，因此被认为是一个特别高的地区地震危险。与此类事件相关的结构和变形方式仍然知之甚少。

在这项研究中，我们分析了来自国家和国际台站 4 个月的区域地震记录，以描述 10 月 28 日发生中等震级（M _W  = 4.8 和 M _L = 5.2）地震后的 74 个地壳事件序列, 2019 我们使用区域矩张量反演来约束源参数。

该分析还包括从 P 波极性和 P-S 波幅度比确定 11 种震源机制。大多数焦点机制指示反向运动解决方案。

然后将地震学结果与其他地球物理学（重力和地震反射剖面）以及地质数据相结合，构建一个 3D 结构模型，以便更好地了解研究区的地壳变形机制。

我们的研究结果表明，地震变形主要集中在西部Precordillera的基底，在与前山脉的过渡处。这种变形似乎对压缩应力有反应。提议的模型提供了与前科迪勒拉山脉的厚皮变形与西前科迪勒拉山脉的薄皮褶皱和逆冲带之间相互作用相关的正在进行的地震活动的证据。