Underground traffic activities spread ground-borne vibrations in a complex way. The present work focuses on 173 individual vehicles tracked as moving sources of vibrations in the Mont Terri rock laboratory, located 95 m away from a motorway tunnel. Two neighboring geophones record the vertical ground velocity of traffic-induced events with peak particle velocities ranging in 0.15–0.35 m/s. A dynamic cross-correlation of the waveforms is used to align the individual events for coherent and robust analysis. A root mean square (rms) method allows identifying the main feature, centered at the Main Fault, and an unexpected feature located about 140 m apart. The dominant seismic frequencies are 15 and 10 Hz, respectively. The vehicle speeds (70–90 km/h), estimated from the time-delay between the two features, and the seismic velocity (800–2,300 m/s), assessed from a simple kinematic model, are used to convert time to position along the tunnel, allowing modeling the local rms with the Bornitz's equation. The resolved frequency-independent attenuation coefficients are 2.61 s/km in the Opalinus Clay including the gallery network, and 1.23 s/km in the Limestone, a contrast of elastic properties that defines a bimaterial interface. A particle motion analysis highlights body waves, with dominant vertically polarized shear waves above the Main Fault. The origin of the unexpected feature is discussed in terms of site effects and seismic propagation in a heterogeneous fracture network. Traffic-induced events can be used as reproducible, low-frequency, and non-destructive sources with potential interest in long-term monitoring at the scale of an underground gallery.

中文翻译：

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地下交通诱导体波用于量化主断层附近双材料界面的地震衰减特性

地下交通活动以复杂的方式传播地面振动。目前的工作重点是在距高速公路隧道 95 m 的 Mont Terri 岩石实验室中跟踪 173 辆作为移动振动源的车辆。两个相邻的地震检波器记录了交通诱发事件的垂直地面速度，峰值粒子速度范围为 0.15-0.35米/秒。波形的动态互相关用于对齐各个事件以进行连贯和稳健的分析。均方根 (rms) 方法允许识别以主断层为中心的主要特征和相距约 140 m 的意外特征。主要地震频率分别为 15 和 10 Hz。根据两个特征之间的时间延迟估计的车辆速度 (70–90 km/h) 和从简单运动学模型评估的地震速度 (800–2,300 m/s) 用于将时间转换为位置沿隧道，允许使用博尼茨方程对局部均方根进行建模。解析出的频率无关衰减系数在 Opalinus 粘土（包括画廊网络）中为 2.61 s/km，在石灰岩中为 1.23 s/km，这是定义双材料界面的弹性特性的对比。粒子运动分析突出了体波，主要断层上方的垂直极化横波占主导地位。意外特征的起源是根据现场效应和非均质裂缝网络中的地震传播来讨论的。交通引发的事件可用作可重复的、低频的和非破坏性的来源，对地下通道规模的长期监测具有潜在兴趣。