Glasses broke and furniture moved at Premier House, the official prime ministerial residence in Wellington, Mr. Key said. He had stayed there overnight after meeting with Secretary of State John Kerry, who was on a state visit there and to Antarctica.

Geoscience Australia said the 6.4-magnitude earthquake was one of three large aftershocks that measured between 5.1 and 6.4 magnitude. There have been at least 12 aftershocks since early Monday morning in New Zealand.

Caroline Little, a spokeswoman for GeoNet New Zealand, which monitors geological hazards, said seismologists had modeled the probability of the number and intensity of aftershocks on Monday morning.

“The initial earthquake was a complex rupture,” she said in a telephone interview. “It was one quake, but there were a number of fault segments and a series of orientations in terms of the way the energy was released.” She described it as a zigzag rather than a single fault and said this would affect the way aftershocks played out. “We expect aftershocks for weeks, maybe months,” she said.