Understanding the factors controlling fracture frequency distribution can greatly improve the assessment of fluid circulation in fault damage zones, with evident implications for fault mechanics, hydrogeology and hydrocarbon exploration. This is particularly important for relay zones that are usually characterized by strong damage and structural complexity. We investigated the fracture frequency within an outcrop adjacent to the front fault segment of a relay ramp, hosted within peritidal carbonates that forms part of the Tre Monti fault (Central Italy). We analysed the distribution of fracture frequency in the outcrop through (1) scanlines measured in the field, (2) oriented rock samples, and (3) scan-areas performed on a virtual outcrop model. Fracture frequency increases with distance from the front segment of the relay ramp. Moreover, supratidal and intertidal carbonate facies exhibit higher fracture frequency than subtidal limestones. This trend of increased fracture frequency has two main explanations. (1) The number of subsidiary faults and their associated damage zones increases moving away from the front segment. (2) the supratidal and intertidal carbonate facies content increases toward the centre of the relay ramp. Our results indicate that the fracture frequency pattern is very complex in relay ramps hosted in shallow-water limestones and that its prediction necessitates a good control on structures and sedimentary facies distribution.

中文翻译：

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碳酸盐岩中继斜坡内裂缝频率分布的岩性和构造控制

了解控制裂缝频率分布的因素可以大大提高断层损伤带流体循环的评估，对断层力学、水文地质和油气勘探具有明显的意义。这对于通常以严重损坏和结构复杂为特征的接力区尤为重要。我们调查了与接力坡道前断层段相邻的露头内的断裂频率，该断层位于构成 Tre Monti 断层（意大利中部）一部分的潮间带碳酸盐岩内。我们通过 (1) 现场测量的扫描线、(2) 定向岩石样本和 (3) 在虚拟露头模型上执行的扫描区域分析了露头中裂缝频率的分布。断裂频率随着距继电器斜坡前段的距离而增加。而且，潮上和潮间带碳酸盐岩相的破裂频率高于潮下灰岩。这种骨折频率增加的趋势有两个主要解释。(1) 远离前段的次要断层及其相关损伤带的数量增加。(2) 潮上、潮间带碳酸盐岩相含量向中继斜坡中心增加。我们的结果表明，浅水石灰岩中的接力斜坡的裂缝频率模式非常复杂，其预测需要对构造和沉积相分布进行良好控制。(1) 远离前段的次要断层及其相关损伤带的数量增加。(2) 潮上、潮间带碳酸盐岩相含量向中继斜坡中心增加。我们的结果表明，浅水石灰岩中的接力斜坡的裂缝频率模式非常复杂，其预测需要对构造和沉积相分布进行良好控制。(1) 远离前段的次要断层及其相关损伤带的数量增加。(2) 潮上、潮间带碳酸盐岩相含量向中继斜坡中心增加。我们的结果表明，浅水石灰岩中的接力斜坡的裂缝频率模式非常复杂，其预测需要对结构和沉积相分布进行良好控制。