Two more strong earthquakes shook the coast of the Indonesian island of Sumatra on Thursday, after the powerful quake that hit on Wednesday, but the area escaped a major tsunami like the one that devastated the region in 2004.
More than a dozen people were reported to have died in the earthquakes, and hundreds of buildings were damaged in the coastal cities of Padang and Bengkulu in western Sumatra.
The shaking continued through the day Thursday, keeping residents on edge. Some fled to higher ground away from the coastline; many more camped outdoors in the streets and parks.
The first and biggest of the shocks, with a magnitude of 8.4 on Wednesday evening, was the third in a cluster of earthquakes in the area in the past three years of a magnitude of more than 8.0.
That cluster could be a signal that the western coast of Sumatra, which stretches 1,100 miles, could face still more danger, scientists say.
“I am more convinced than ever that we are going to be seeing a significantly larger earthquake in the area,” said Kerry Sieh, a seismologist from the California Institute of Technology who has spent several decades studying earthquake risk around Sumatra.
“These three big earthquakes, they just encircle this big patch that has not failed, a big strong part of the fault that hasn’t broken yet,” he said. “The million-dollar question is: Is it over?”
Bengkulu, a city of 1.2 million, was the closest large community to the latest earthquakes, and it had the most damage. The epicenter of the first quake was about 60 miles southwest of the city; the second was about 125 miles to the northwest.
The major earthquake on Wednesday was followed by a series of aftershocks, and one of them, on Thursday morning, was a serious earthquake on its own. It struck almost 200 miles northwest of the epicenter of the earlier earthquake and had a magnitude of 7.8. It was followed shortly before noon by another significant earthquake, with a magnitude of 7.1.
As the earth shook along the Sumatran coast, tsunami warnings were repeatedly issued and then withdrawn by governments in Asian and African countries along the Indian Ocean.
The range of nations on the alert reflected the damage done in December 2004, when a tsunami took an estimated 230,000 lives on the Indian Ocean rim, with the heaviest death toll in Aceh province in northern Sumatra.
In recent months, Padang had stepped up a public education campaign, drawing on the lessons of Aceh. Residents there headed for higher ground in a relatively orderly way after the latest quakes, one earthquake monitor said.
“A few people panicked, but the city is under control,” said Patra Rina Dewi, who leads an organization called Kogami, which has been educating residents about earthquakes and tsunamis. “Our mayor was on the radio giving instructions to the community and to agencies about what they should do.”