JAKARTA, INDONESIA — A powerful and shallow earthquake struck the Molucca Sea off the island of Sulawesi in eastern Indonesia on Saturday morning, prompting a tsunami warning for local coastlines, seismologists said. There was no immediate word on damage or casualties.
The 7.3-magnitude earthquake at 9:31 a.m. local time (0231 GMT) was centered in the Molucca Sea about 155 kilometers (96 miles) east-northeast of Bitung, a city on the northern coast of the island of Sulawesi. It struck about 48 kilometers (29.8 miles) below the seabed, making it a shallow earthquake, according to the country's seismological agency (BMKG).
BMKG said a tsunami warning was in effect for coastlines of the Molucca Sea, but it was not immediately known whether a tsunami had been generated.
The Pacific Tsunami Warning Center, which said there was no threat of a Pacific-wide tsunami, said hazardous tsunami waves of up to 1 meter (3.2 feet) above tide level were possible within 300 kilometers (186 miles) of the epicenter. Smaller waves could potentially reach southern coastlines of the Philippines, where no tsunami alert was in effect.
"Government agencies responsible for threatened coastal areas should take action to inform and instruct any coastal populations at risk in accordance with their own evaluation, procedures and the level of threat," the center said in a bulletin. "Persons located in threatened coastal areas should stay alert for information and follow instructions from national and local authorities."
Computer models from the Pacific Tsunami Warning Center showed that tsunami waves, if generated, could have begun reaching coastlines from 10:04 a.m. local time (0304 GMT). "Actual arrival times may differ and the initial wave may not be the largest. A tsunami is a series of waves and the time between waves can be five minutes to one hour," it cautioned.
The United States Geological Survey (USGS), which measured the earthquake at 7.1, said it did not expect to see damage or casualties from the earthquake itself as it struck relatively far off land. Computer models estimated that approximately 83,000 people close to the epicenter may have felt moderate tremors, while up to 3.3 million people further away may have experienced weak to light shaking.
A second strong earthquake, which BMKG measured at 6.3 at a depth of just 59 kilometers (36.6 miles), followed about 30 minutes later in another part of the Molucca Sea, about 153 kilometers (95 miles) east of Gorontalo. The second earthquake struck far to the southwest of the initial quake and it was not immediately clear whether it was an aftershock or a second event.
Indonesia is on the so-called 'Pacific Ring of Fire', an arc of fault lines circling the Pacific Basin that is prone to frequent and large earthquakes. In December 2004, a magnitude-9.1 tremor, one of the most powerful earthquakes ever recorded, struck off the west coast of Sumatra, unleashing a massive tsunami that struck scores of countries in the region and killed at least 227,898 people.
More recently, in July 2013, at least 35 people were killed and more than 270 others were injured when a strong 6.2-magnitude earthquake struck the province of Aceh on the island of Sumatra. The tremors destroyed more than 1,900 homes in the region and damaged nearly 2,400 others.