The June 13 event was witnessed near shore by a fisherman and others who were dragged around by the waves. That event coincided with a derecho wind event that is suspected of blowing water out to sea.
The tsunami was recorded by buoys from Massachusetts to North Carolina, which also suggests that it was driven by the weather and not by a submarine landslide, ten Brink explained. That's because undersea landslides tend to be relatively local, and create pulses of energy that can make tsunamis nearby, but the waves weaken very quickly with distance.
The April 11 event, on the other hand, was recorded by buoys and occurred without any unusual weather to explain it. The next logical cause is an undersea landslide. That's what sent the Okeanos Explorer to see if there has been any change in Hudson Canyon, which slices into the edge of the continental shelf about 100 miles off the coast of New Jersey and Long Island.