If a 3.9 was responsible for the building collapse then it didn't even meet the requirements for Florida's hurricane building code. A tornado of E4 size is strong enough to register a 4.5 on the seismic scale.

The building collapse has zero to do with the Navy shock testing an aircraft carrier. It has everything to do with age, lack of maintenance, fraud as far as the possibility that inspectors were paid to look the other way, lack of proper amounts of steel rebar specified by the engineers in the designs.

It's not something new and not limited to the US Navy or just aircraft carriers. Shock test are conducted routinely by the Royal Navy, China and many others so yes you will see a pattern.

As for location, no they cannot just do it anyway. First requirement is safety. They must find a location outside of the regular shipping lanes of both commercial and other military vessels, second, they need a location of the proper depth and one where ecological damage as in away from vulnerable coral reefs and other sea life will be minimal.

And preferably a close proximity to ports capable of hosting a ship that size in the event of test failure as the crew is aboard at the time of explosion. No the explosion did not cause the collapse of that building. Have you ever been in a building and a train close by passes ? I can imagine it would register on sensitive seismic equipment.

Please do not make this into something it's not...a conspiracy as the test were announced far in advance and carried out in full view of the public as numerous videos are available