My immediate thought on finding caves was rather star trekian and involved lots of data processing and comparison of
thermal sensing data and patterns.
If a more immediate solution is required I would think about designing a robot to crawl in with a seismometer and
a satellite transmitter link. An F-15, F16, or F-14 could detonate a rocket at a laser designated site when enough
of the robot squads were in place to take readings. Then the siezmotransports crawl on to the next location and
wait for the next flyby or buzz bomb to impact.
Clearly there would be substantial attrition of these throwaway robots. Perhaps they could be equipped with some
primitive arms operated via teleoperations (we would not want a kid to trigger an attack upon themselves) or commands
so that if discovered by hostile terrorist forces they could take pot shots back and keep the terrorists pinned down for
a while before attempting a kamikaze run on the nearest terrorist.
It is worth noting that such robots would have a lot of useful components so the design should verifiably destroy most of
the most militarily valuable components or the terrorsts would soon be sending these back to civilization's cities, outposts,
neighborhoods, and/or parks.
It is also worth noting that judicious stage acting would allow delivery of useful materials and wealth to double agents
or freedom fighters in the area under guise of preparation for an overt U.S. military attack. While terrorist leaders
waste their resources watching for paratroopers local freedom fighters might be eroding their support base until an
almost bloodless coup or a final battle in defense of the free villages computer centers and schools solved the problem
of thugs in charge.
Clearly once the thug governments are gone tactics will have to change so we are not arming barbarians with advanced
technology allowing them to be more of a nuiscance than would otherwise be the case.
While an intelligent barbarian can probably duplicate anything in the field that civilization's advanced manufacturing processes
can put out, it takes a lot of time and effort compared to walking into a military command post and requesting a security
sweep of the neighborhood via robotic security forces because a barbarian was spotted crossing the SOSUS borders of the
local parks.