[walrus01]

I would guess that they want to simulate a percentage of the shock force of a near miss or hit from a (russian, chinese, other equivalent-tech) torpedo or naval mine without actually risking rupturing the hull. So they need a much greater weight of explosives positioned a much further distance away than if they were to actually fire a torpedo at the ship.

Or for general shake and vibration and shock force testing of the entire ship, simulating a combat environment. Unlike the shake/rattle/hydraulic ram rigs which are used to qualify a new airliner design on a structural test article, there's no other way than lots of explosives to shake/vibrate an entire Nimitz, Ford class size aircraft carrier.

[jandrewrogers]

I would guess they want a large enough explosion to generate peak acceleration of the entire ship without a local enough explosion to actually damage it. Getting enough separation to make it non-local requires a lot of explosive thanks to the inverse cube law.

If you look at e.g. seismic damage models, peak acceleration is correlated with most of the worst outcomes.