6.4 Magnitude Earthquake Hits Puerto Rico. The quake struck the U.S. territory at 4:24 a.m. local time Tuesday, killing one and causing an island-wide power outage. . The earthquake is the largest in a series of recent quakes affecting the island. We expect that this will be the largest quake for now. The aftershocks will continue for some time. , Director of Puerto Rico’s Seismic Network Víctor Huérfano. A 5.8 magnitude quake that hit the coast early Monday morning collapsed and damaged several homes and historic sites. Power is expected to be restored later Tuesday