UPDATE: The slide took place at State Line Lookout.
According to scientist Won-Young Kim of the Lamont-Doherty Earth Observatory of Columbia University, the whole rockslide motion took about 35 seconds.
The seismic signals were strong at all three stations in Palisades, NY starting at 7:28 p.m. May 12.
"The duration of the strong signal is about 21 seconds, followed by weaker ground motion for additional 15 seconds, so the whole rockslide motion took about 35 seconds. Is this what people experienced?" Dr. Kim said in an email to Eric Nelsen at the Palisades Interstate Park in Alpine, NJ.
It was Nelsen who alerted the observatory to the rockslide.
"Our police department started receiving calls from across the river at around 7:45 that evening," Nelsen said when asking Dr. Kim if the slide park staff experienced was what caused the strong signal captured on the observatory's website.
A screenshot of Lamont-Doherty's seismographic data is attached to this report.
A Hastings resident sent us this report:
Saturday night a large portion of the Rock Face from the Palisades Park let loose, it took out all the trees that were previously in that area. Leaving a large cloud of smoke from the debris hovering over the water. I live in Hastings and this is directly across the river, on the NJ side.
Anyone know exactly where this is? Please give us details—and add your photos .