Keynote Talk

Alireza Malehmir
Professor of Geophysics
Department of Earth Sciences, Uppsala University

In this work, a development work using a GPS-time prototype is presented. The system allows time-synchronized surveys in GPS denied underground mining environment. With a maximum drift on the order of only a portion of microsecond per day, the system transmits simulated false or real GPS-time signal without cabling from the surface. This provides opportunities for geophysical surveys in deep exploration and mining tunnels where access to such a signal is cost ineffective via surface cabling or even sometimes impractical. A background to how such a system was realized first is presented and then two surveys showcasing how-to and what-for. The first case is from the Neves-Corvo mine (Portugal) at 650 m depth and the second one from the South Deep gold mine (South Africa) at approximately 3000 m. The synchronized recorders so far include nodal, central acquisition, and fiber-optic interrogators, source zero time, a few to mention. The system is currently planned to be ruggedized for more extensive passive and active surveys within the scope of Hub1-Green Sensing Tech of the Smart Exploration Research Center.