Megathrust earthquakes like the 1964 event tend to produce longer durations and periods of shaking, said Jibson, which could trigger more and larger landslides. The 2018 Anchorage intraslab quake, on the other hand, originated within a tectonic plate and at a greater depth than the 1964 quake. The 1964 Alaska quake was a megathrust event, where the rupture took place along the subducting boundary between two tectonic plates. Other differences between the 19 earthquakes might help to explain these findings, said Jibson. 'I think was well below what it would take for them to really take off and move again.'Īfter a major survey of ground failures caused by the 2018 earthquake, Jibson and his colleagues also noted many fewer landslides - several thousands fewer - than would be predicted for the area from landslide modeling based on earthquake magnitude. In places like Government Hill and Turnagain Heights, where devastating landslides had taken place in 1964, there were 'cracks in the places where they had moved in 1964, but they just kind of oscillated in place,' Jibson said.

The shaking that accompanied the 2018 earthquake was of a higher frequency and a shorter duration than shaking during the 1964 quake, both of which probably kept the 1964 landslides from moving downslope again, said Randall Jibson of the U.S.

7.1 alaska quake