The quake was centered just southeast of Christchurch, which sits midway down the east coast of New Zealand's South Island. The shaking ripped down walls of older masonry churches and historic buildings in addition to damaging newer structures.
The highest ground acceleration recorded was close to twice the force of gravity, said Susan Hough, seismologist with the U.S. Geological Survey in Pasadena. "That's quite extreme shaking" and stronger than the movement in Haiti last year and Northridge in 1994, she said.
The damage to earthquake-resistant buildings may indicate "we still have some things to learn" about improving building codes, Hough said.
The quake also provided dramatic evidence of the threat a major earthquake poses even after the jolt may have begun to fade from memory. Seismologists said Tuesday's quake was an aftershock to a magnitude 7.1 quake that hit New Zealand on Sept. 4. That quake was deeper and caused no fatalities.
Thomas Jordan, director of the Southern California Earthquake Center at USC, said the most destructive quake can be an aftershock to the main quake. Aftershocks of New Zealand's September quake have been moving eastward in recent months, closer to Christchurch.
"Earthquakes don't happen individually, but in sequences. We have to be prepared that when we get large earthquakes in California that we recognize that that means the seismic hazard has gone up, not down. One earthquake does not mean the end of story," Jordan said.
New Zealand's worst earthquake, on the North Island, hit in 1931 and killed more than 250 people.
Times staff writers Rich Connell, Sam Allen and Rong-Gong Lin II in Los Angeles contributed to this report.