A fault slip within the Ñaña tunnel Lima, Peru has been monitored since 2012. The data are recorded using an optical-mechanical 3D extensometer, capable of providing very precise long-term three-dimensional measurements of relative displacement across discontinuities. The Ñaña tunnel has an extremely stable environment and cannot possibly be affected by gravitationally-induced mass movements. The host rock of the tunnel is an aphanitic hornblende-bearing basaltic trachyandesite. Several fault and fracture zones detected in the tunnel represent the major discontinuities of the broader surrounding of the monitored site. The recorded fault slip on the NNW-SSE and E-W striking fracture and fault, with inclinations of 76° to WSW and 78° to N respectively, appoint to compressional event (discontinuity contraction) with a maximum horizontal compression stress axis oriented approximately WSW to ENE corresponding to the direction of the Nazca and South America plates convergence. This event resulted in an aseismic slow fault slip between July 2012 and May 2013. The anticipated compression orientation matches the previously published in-situ stress measurements and fault plane solutions, as well as GPS measurements of the movements of the corresponding part of the Peruvian coast. Nevertheless, the presented monitoring results reflect only short-term fault slip dynamics and need to be considered with caution, even though they correspond to the overall tectonic activity driven by continental subduction.

中文翻译：

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在秘鲁利马的Casma集团的安山岩中检测到瞬时压缩断层滑动

自2012年以来，一直在秘鲁的利阿那隧道（Lia）内进行断层滑移监测。使用光学机械3D引伸计记录数据，该引伸计能够提供非常精确的长期三维测量，以测量不连续处的相对位移。Ñaña隧道的环境极为稳定，不可能受到重力引起的质量运动的影响。隧道的主体岩石是含角闪石的玄武质玄武质砂岩。在隧道中检测到的几个断裂带和断裂带代表了受监测站点更广泛的周围环境的主要不连续性。记录的NNW-SSE和EW破裂和断裂上的断层滑动，分别相对于WSW倾斜76°和相对于N倾斜78°。任命具有最大水平压缩应力轴的压缩事件（间断性收缩），该最大压缩应力轴的方向近似于WSW到ENE，对应于纳斯卡和南美板块汇合的方向。此事件导致2012年7月至2013年5月之间发生了地震作用的缓慢断层滑动。预期的压缩方向与先前发布的原地应力测量和断层平面解以及秘鲁海岸相应部分的GPS测量相匹配。 。尽管如此，本文给出的监测结果仅反映了短期断层滑动动力学，即使与大陆俯冲驱动的整体构造活动相对应，也应谨慎考虑。