To evaluate and upscale the feasibility of using exploration tunnels in an operating mine for active-source seismic imaging, a seismic experiment was conducted at the Neves-Corvo mine, in southern Portugal. Four seismic profiles were deployed in exploration drifts approximately 650 m beneath the ground surface, above the world-class Lombador volcanogenic massive sulfide deposit. In addition to the tunnel profiles, two perpendicular surface seismic profiles were deployed above the exploration tunnels. The survey was possible due to a newly developed prototype global positioning system (GPS) time transmitter enabling accurate GPS synchronization of cabled and nodal seismic recorders, below and on the surface. Another innovative acquisition aspect was a 1.65 t broadband, linear synchronous motor (LSM) driven — electric seismic vibrator (e-vib) used as the seismic source along two of the exploration tunnels. We have evaluated the challenges and innovations necessary for active-source tunnel seismic acquisition, characterized by high levels of vibrational noise from the mining activities. In addition, we evaluated the LSM vibrator’s signal and overall seismic-data quality in this hard rock mining environment. Our processing results from the tunnel data and 3D reflection imaging of the Lombador deposit below the exploration tunnels were checked for consistency through constant-velocity 3D ray-tracing traveltime forward modeling. For imaging purposes, 3D Kirchhoff prestack depth and poststack time-migration algorithms were used, with both successfully imaging the targeted deposit. The results obtained show that active-source-seismic imaging using subsurface mining infrastructure of operational mines is possible. However, it requires innovative exploration strategies, a broadband seismic source, an accurate GPS-time system capable of transmitting GPS-time hundreds of meters below the surface, and careful processing. The results obtained open up possibilities for similar studies in different mining or tunneling projects.

中文翻译：

---

葡萄牙内维斯-科尔沃，火山成块状硫化物矿床的创新地震成像—第1部分：矿井阵列

为了评估和扩大在运营中的矿井中使用勘探隧道进行有源震源成像的可行性，在葡萄牙南部的Neves-Corvo矿山进行了地震实验。在世界级的Lombador火山成因块状硫化物矿床上方约650 m的地表勘探巷道中部署了四个地震剖面。除了隧道剖面外，在勘探隧道上方还部署了两个垂直的地面地震剖面。由于新开发的原型全球定位系统（GPS）时间发送器能够在地面下和地面上对有线和节点地震记录仪进行精确的GPS同步，因此该调查得以实现。另一个创新的收购方面是1.65吨宽带，线性同步电动机（LSM）驱动—电动地震振动器（e-vib）沿两条勘探隧道被用作地震源。我们评估了主动源隧道地震采集所必需的挑战和创新，其特点是采矿活动产生的高水平振动噪声。此外，我们在这种硬岩开采环境中评估了LSM振动器的信号和整体地震数据质量。我们通过等速3D射线追踪行进时间正演模型检查了隧道数据和勘探隧道下方Lombador矿床的3D反射成像的处理结果是否一致。出于成像目的，使用了3D Kirchhoff叠前深度和叠后时间偏移算法，并且都成功地对了目标矿床进行了成像。获得的结果表明，使用运营矿井的地下采矿基础设施进行主动源地震成像是可能的。但是，它需要创新的勘探策略，宽带地震源，能够在地表以下数百米范围内传输GPS时间的精确GPS时间系统。获得的结果为在不同的采矿或隧道项目中进行类似研究提供了可能性。