The existence of active faults hidden below Quaternary alluvium is a common geological scenario for intermontane basins, such as the areas struck by the recent earthquakes in Central Italy, and is of great importance for seismic hazard evaluation. Finding hidden faults is a challenging task from the geophysicist's point of view since the goal is twofold: to identify the seismic bedrock at a certain depth; and to detect lateral variations or dislocations that may indicate the presence of a fault. We propose a mixed approach encompassing at first single‐station seismic noise measurements, to detect sudden lateral variations in the bedrock surface in a fast and cost‐effective way, which might serve as a proxy for the potential identification of fault zones. Then, more accurate electrical resistivity tomography investigations are carried out only at selected sites as indicated by the preliminary noise analysis, as electrical methods cannot effectively be employed at a large scale for time and economic limitations. Surface‐wave dispersion analysis is jointly interpreted together with ambient noise data to improve the seismic characterization of the alluvium, giving further insight on the assessment of the depth to bedrock. The proposed approach can be an effective way to manage and investigate a large portion of the territory within a sensible budget, as commonly needed in seismic hazard assessment and microzonation studies. We present a real‐world application to the San Vittorino Plain (Central Italy) close to the epicentre of the 24 August 2016 Amatrice earthquake, where the geological faulted bedrock is covered by alluvial sediments of the Velino River up to a maximum estimated thickness of 150–200 m. Although engineered for the post‐earthquake reconstruction emergency, the approach employed in our study can be adopted in other areas of similar geology, to ease the application of seismic microzonation in time of seismic silence as a tool for long‐term land planning and management.

中文翻译：

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用于识别冲积层以下活动地震断层的地震勘探评估的地球物理研究

隐藏在第四纪冲积层之下的活动断层是山间盆地的常见地质情况，例如意大利中部最近地震袭击的地区，这对评估地震危险性非常重要。从地球物理学家的角度来看，发现隐藏的断层是一项具有挑战性的任务，因为目标是双重的：识别一定深度的地震基岩；并检测可能表明存在断层的横向变化或错位。我们提出了一种混合方法，该方法包括在最初的单站地震噪声测量中，以快速且经济高效的方式检测基岩表面的突然横向变化，这可以作为潜在识别断层带的代理。然后，由于初步的噪声分析表明，由于时间和经济上的限制，不能有效地大规模采用电气方法，因此只能在选定的位置进行更准确的电阻层析成像检查。将表面波频散分析与环境噪声数据一起进行解释，以改善冲积层的地震特征，从而进一步评估基岩深度。提议的方法可能是在合理的预算范围内管理和调查大部分领土的有效方法，这是地震危险性评估和微区划研究中通常需要的。我们向2016年8月24日阿马特里切地震的震中附近的圣维托里诺平原（意大利中部）提供了一个实际应用程序，地质断层基岩被维利诺河的冲积沉积物所覆盖，最大估计厚度为150–200 m。尽管专为地震后重建紧急事件而设计，但我们的研究中采用的方法可以在其他类似地质领域中采用，以缓解地震微带化在地震静息时作为长期土地规划和管理工具的应用。