Catchings suggests that more seismometers should be deployed in and around Washington and other cities along the eastern seaboard, to assess to what degree seismic waves generated in the region might be amplified. “My guess is, it’s going to be substantial,” he notes — possibly as much as three to five times the values normally expected. Besides shedding light on seismic risk, this exercise would reveal whether particular buildings need to be retrofitted in order to stand up to future quakes.
The unusually large ground motions for a magnitude-5.8 quake also triggered rockfalls across an unexpectedly large area, reported Randall Jibson, a geologist with the USGS in Denver. He and a colleague surveyed the area surrounding the quake for fresh landslides in the days immediately after the event. None of the rockfalls caused any damage or injuries.
Although individual landslides weren’t especially large, the pattern of rockfalls set a record. Previous studies suggested that a magnitude-5.8 quake shouldn’t trigger landslides more than 60 kilometers from its epicenter, says Jibson. But last year’s quake caused rockfalls at least 245 kilometers away, he reported. “This is by far the largest distance recorded for a quake that size,” he notes.