[ExI] Tunnels

[BillK]

On Sun, Jul 20, 2014 at 12:27 AM, David Lubkin wrote:
> Are there any credible technologies, either current or plausible future,
> that can stymie tunneling by wealthy, motivated opposition along ranges from
> (say) 10^2 to 10^6 meters --at least by anything less than a hypothetical
> shaped nuclear charge, MNT disassemblers, or the sort of large, expensive
> tunnel boring machine that is hard to obtain or conceal?
>
>

Ground penetrating radar as used by archaeologists? Can detect voids
up to 15 metres below the surface, depending on the soil structure.
<https://en.wikipedia.org/wiki/Ground-penetrating_radar>

Back in medieval times and WWI, listening devices were used to detect
the sounds of tunnelling.

BillK