The U.S. Navy's use of explosives to test ships can be confused for earthquakes.
The goal of the trials is to make sure newly built ships can sustain underwater explosions.
Each blast was created with 10,000 pounds of explosives.
With all those explosives comes a serious risk of danger to both humans and wildlife.
The U.S. Navy says it notifies mariners ahead of the testing. It also says it monitors for mammals in the water and doesn't conduct testing if a mammal is nearby.
The U.S. Navy reports the USS Jackson fared well and had little damage.
This was the first FSST since 2008, but it wasn't the last.
The U.S. Navy put the USS Milwaukee through its first test explosion in early September. And just like the USS Jackson, it registered as seismic activity.