A magnitude 8.7 quake shook Indonesia's west coast, killing hundreds of people and spreading panic across the Indian Ocean that another killer tsunami was on the way.

There was no destructive tsunami generated, but a small wave was detected by a tide gauge on Cocos Island near Australia, about 1,500 miles south of the epicenter, according to the Pacific Tsunami Warning Center.

"I'm baffled an earthquake this size didn't trigger a tsunami near the epicenter," said Robert Cessaro, a geophysicist at the center, which is operated by the National Oceanic Atmospheric Administration, or NOAA.

Charles McCreery, director of the center charged with monitoring seismic and ocean conditions in the Pacific and alerting Pacific Rim nations and U.S. agencies, said earthquakes of at least 8.0 magnitude usually generate major tsunamis.

"We expected some destructive tsunami with some distant destructive effects. It was surprising," he said.

The latest event also demonstrated "there's a whole world of uncertainty about trying to judge a tsunami based on the earthquake data," he said.

The warning center initially estimated the Dec. 26 earthquake — which killed at least 175,000 people in 12 Indian Ocean nations and left another 106,000 missing — to have a magnitude of 8.0, but it turned out to be much larger — a 9.0.

Today's preliminary estimate was higher, magnitude 8.5, but had no destructive tsunami.

"The one we initially thought was bigger turns out to have no effect," McCreery said. "The one we initially thought was smaller had a huge effect. This is the challenge of tsunami warning."

The warning center, established in 1949, came under heavy criticism following the December tsunami for not being more aggressive about warning Asian nations and possibly saving thousands of lives.

Earlier this month, a group of 58 European tsunami survivors and relatives of victims sued NOAA and other agencies, alleging the center did not do enough to warn people about the disaster.

NOAA officials noted the center has "no official responsibility" for the Indian Ocean and they previously had no communications set up with countries in that area.

"Although we certainly wish that somehow the event unfolded in a way that we could've done more for the region, we really did all we could under the circumstances," McCreery said. "I'm confident there won't be much to come from this lawsuit."

Since then, several Indian Ocean nations have established communications with the center and are now on the center's alert list.

Today, the facility was able to alert those nations with its bulletins electronically, by e-mail, fax and some were also called as a backup.

"I think we had more success this time being able to get information out quickly to areas in the region, so they can take some action and get people out of harm's way," McCreery said.

The Indian Ocean currently has no warning center similar to the one in Hawai'i.

"But we have agreed to provide this information in an effort to save lives," McCreery said. "We issued the information about the strong possibility of tsunamis in the region. We have understood from the phone calls we've been making today that they did receive the bulletin and were able to act on them."

Scientists said the biggest difference for the quick response this time around is that there is heightened awareness of tsunamis.

"In the case of the Indian Ocean, we could yell, 'tsunami,' but until that event happened, nobody would know what to do," Cessaro said.