Establishing genetic links between active shallow faulting and deep seismogenic sources is challenging, especially in areas where seismogenic faults lack clear and readily interpretable geological evidence at the surface. The architecture of the Pedeapenninic margin of the Northern Apennines (Italy) reflects a regional-scale and complex NE-verging blind thrust system, which is dissected by transpressive/transtensive faults resulting from active NE-SW orogenic compression. The local geological framework is defined by allochthonous ocean-derived units resting atop Pliocene-to-present successions exposed along the Northern Apennines margin and to the NE of it, while the innermost chain sector mostly contains Adria-related units. We present results from field structural-geological investigations to identify and characterize potential active faults along the margin. There, the Pliocene-to-present units are faulted and folded, indicating that tectonic activity is still on-going, thus contributing to the local seismic hazard. Top-to-the NE and SW normal faults are common in the area and deform the Pliocene-to-present succession together with NE-SW strike-slip and transpressional/transtensional faults. Based on field evidence, we define four potentially active thrust segments affecting Middle Pleistocene to Holocene deposits exposed along the margin. Calcite U-Th dating on samples from faults extend the most recent datable tectonic activity back to the Middle Pleistocene. Paleostress analysis from inversion of fault-slip data from the most recent identified striated fault planes constrains a NE-SW shortening direction parallel to the Apennines regional migration direction. A distinct but coaxial extensional stress regime, recorded by structures measured within Plio-Pleistocene formations, was also identified. Our results offer a sound starting point for future investigations aimed at improving our understanding of active and seismogenic faulting in the area, so as to create robust Probabilistic Seismic and Fault Displacement Hazard Assessment (PSHA and PFDHA) models that can implement refined seismic hazard maps benefitting from structural-geological deterministic inputs in addition to the classic seismological constraints.

中文翻译：

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北亚平宁山脉（意大利）裸露前沿的近期活跃断层：来自现场和地质年代学限制的新见解


在活跃的浅层断层和深地震源之间建立成因联系是具有挑战性的，尤其是在地震断层缺乏清晰且易于解释的地表地质证据的地区。北亚平宁山脉（意大利）的 Pedeapenninic 边缘的结构反映了一个区域尺度和复杂的 NE 边缘盲推力系统，该系统被活跃的 NE-SW 造山压缩导致的跨压/透展断层分割。当地的地质框架由位于上新世至今的演替之上的异质海洋衍生单元定义，这些演替位于沿北亚平宁边缘及其东北部暴露的演替之上，而最内层的链区主要包含与亚德里亚相关的单元。我们展示了野外结构地质调查的结果，以识别和描述沿边缘的潜在活动断层。在那里，从上新世到现在的单元被断层和折叠，表明构造活动仍在进行中，从而造成了当地的地震灾害。从上到东北和西南的正断层在该地区很常见，并与东北-西南走滑和跨压/跨张断层一起变形了上新世到现在的演替。根据现场证据，我们定义了四个潜在的活跃逆冲段，影响沿边缘暴露的中更新世至全新世沉积物。断层样本的方解石 U-Th 测年将最近的可测年构造活动追溯到中更新世。来自最近确定的条纹断层平面的断滑数据反演的古应力分析限制了平行于亚平宁区域迁移方向的 NE-SW 缩短方向。 还确定了一种独特但同轴的拉伸应力状态，由上更新世地层中测量的结构记录。我们的结果为未来的调查提供了一个良好的起点，旨在提高我们对该地区活跃和地震断层的理解，从而创建强大的概率地震和断层位移危害评估（PSHA 和 PFDHA）模型，这些模型可以实施精致的地震灾害地图，受益于结构地质确定性输入以及经典的地震学约束。