Buried seismic sensors have been used by CBP for years now, there’s an entire program dedicated to using them specifically for detecting tunnels as well. For d

Buried seismic sensors have been used by CBP for years now, there’s an entire program dedicated to using them specifically for detecting tunnels as well. For detecting persons, it’s just an evolution of the existing process with the massive camera setups. Sensed/taped footfalls -> closest CBP station -> agent response