The relay zones between NW-SE to NNW-SSE striking faults of the Jiloca graben (Iberian Chain) mostly show distributed along-strike fault and fracture patterns. The latter are chiefly controlled by the Late Pliocene-Quaternary regional stress field, and secondarily respond to local controls from inherited structures. Such fracture patterns contrast with the classical models of transverse connecting faults controlled by relay kinematics. North of the Concud fault trace, at the relay zone with the Sierra Palomera fault, an unusually high seismic activity has been noticed since 2014, with magnitudes up to M = 3.5. Upgrading of the National Seismic Network allowed obtaining such new detailed records, while the installation of a new seismometer by the IGN within the study area has improved the reliability of focal depth data since 2017. A high-precision absolute relocation of seismicity from 01/01/2000 to 30/05/2022 has been carried out. The results show that (i) the epicentres are significantly clustered along a nearly N-S trending band, and (ii) the focal depths range from 0 to 14 km, in good agreement with the thickness of the brittle crust. This 3D spatial distribution of seismicity is interpreted as a consequence of activation of either a single fault or a fault zone, nearly vertical and N-S striking. Such structural setting is consistent with the surficial fracture patterns observed at both map and outcrop scale: NNW-SSE and NNE-SSW oriented faults and fractures, orthogonal to the ENE-WSW to ESE-WNW regional σ3 trajectories, together with NW-SE trending ones controlled by inherited contractive faults. The present-day seismic activity suggests that along-strike, incipient fault propagation at the relay zone between the Concud and Sierra Palomera faults is currently operating under the control of the remote stress field.

中文翻译：

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当今中继带（西班牙吉洛卡伸展盆地）的早期断层合并：来自仪器地震活动的证据


伊比利亚链（Jiloca Graben Chain）的NW-SE至NNW-SSE走向断层之间的中继带大多呈现分布的沿走向断层和断裂模式。后者主要受晚上新世-第四纪区域应力场的控制，其次响应来自遗传结构的局部控制。这种断裂模式与由继电器运动学控制的横向连接断层的经典模型形成鲜明对比。在 Concud 断层轨迹以北，在 Sierra Palomera 断层的中继带，自 2014 年以来已经观察到异常高的地震活动，震级高达 M = 3.5。国家地震网的升级允许获得这些新的详细记录，而自 2017 年以来，IGN 在研究区域内安装了新的地震仪，提高了焦距深度数据的可靠性。从 2000 年 1 月 1 日到 2022 年 5 月 30 日，已经进行了高精度的地震活动绝对重新定位。结果表明，（i） 震中显著聚集在近 N-S 的趋势带上，以及 （ii） 震源深度范围为 0 至 14 公里，与脆性地壳的厚度非常吻合。地震活动的这种 3D 空间分布被解释为单个断层或断层带激活的结果，几乎是垂直的和 N-S 走向。这种构造设置与在地图和露头尺度上观察到的地表裂缝模式一致：NNW-SSE 和 NNE-SSW 导向的断层和裂缝，与 ENE-WSW 到 ESE-WNW 区域 σ3 轨迹正交，以及由遗传收缩断层控制的 NW-SE 走向。 目前的地震活动表明，Concud 和 Sierra Palomera 断层之间的中继带的沿走向、初期断层传播目前是在远程应力场的控制下进行的。