Powerful Molucca Sea Quake Triggers Tsunami Alerts Across Eastern Indonesia; At Least One Dead

The shaking hit just after sunrise, a violent sideways lurch that sent families in the Indonesian port city of Bitung sprinting barefoot into the street.

“We had just woken up and suddenly the earthquake hit,” said Marten Mandagi, a Bitung resident reached by phone. “We all ran out of the house. The shaking was very strong.”

Minutes later, loudspeakers and mobile phones carried a second jolt: tsunami warnings for parts of North Sulawesi and North Maluku, urging coastal residents to move to higher ground. Crowds climbed hills and waited in open fields, watching the sea.

Tsunami warnings issued, then lifted

A powerful undersea earthquake struck the Northern Molucca Sea on Thursday morning, April 2, local time, triggering tsunami alerts across eastern Indonesia and brief advisories around the western Pacific. The magnitude 7.4 to 7.6 temblor damaged homes and churches, killed at least one person and forced hundreds to evacuate, but early data show it produced only modest sea-level changes and far less destruction than some past disasters of similar strength.

The quake struck at 6:48 a.m. local time (22:48 GMT Wednesday, April 1) beneath the Northern Molucca Sea between North Sulawesi and North Maluku provinces. The U.S. Geological Survey measured it at magnitude 7.4 at a depth of about 35 kilometers. Indonesia’s Meteorology, Climatology and Geophysics Agency, known as BMKG, reported a magnitude 7.6 with a depth of 33 kilometers.

Its epicenter lay roughly 120 to 130 kilometers northwest of Ternate, in a complex zone where several tectonic plates collide. BMKG said the quake was caused by thrust faulting—a megathrust-type event—capable of deforming the seafloor and generating a tsunami.

Shaking reached intensity levels of V to VI on the Modified Mercalli scale in Ternate and parts of nearby Halmahera, strong enough to crack walls and send furniture toppling. Residents in Manado and Bitung, major cities on the North Sulawesi coast, reported shaking that lasted 10 to 20 seconds.

Within two minutes and 45 seconds of the quake, BMKG issued its first bulletin, identifying the earthquake and warning of tsunami potential. The agency assigned “Siaga” (standby) alert levels to several coastal areas including Ternate, Halmahera, Tidore and Bitung, and a lower “Waspada” (watch) level for more distant islands.

By that point, tens of thousands of people along the coast had already begun moving uphill, many acting on drilled-in instincts from years of disaster messaging and memories of past tsunamis.

“BMKG must, within less than three minutes, issue a first tsunami warning with the earthquake parameters, tsunami potential, arrival time and threat level,” the agency’s head, Teuku Faisal Fathani, said in a briefing after the quake. He added that staff immediately monitored nine tide gauges in the region and coordinated with regional tsunami centers.

The Pacific Tsunami Warning Center in Hawaii also issued a bulletin, saying “hazardous tsunami waves are possible for coasts located within 1,000 kilometers of the epicenter,” including parts of Indonesia, the Philippines and Malaysia. Civil defense agencies in those countries later clarified that no significant tsunami was expected on their shores.

Instrument readings inside Indonesia recorded small but distinct waves. Tide gauges showed sea-level rises of around 20 centimeters in Bitung and 30 centimeters in western Halmahera, with BMKG saying maximum amplitudes at some points reached about 75 centimeters. Officials cautioned that even modest offshore waves can be amplified in narrow bays and inlets, but there were no reports of major inundation.

As field reports came in and gauges stabilized, BMKG canceled the tsunami early warning later that morning.

Casualties and damage reports

In the meantime, damage assessments began to filter in from North Sulawesi and North Maluku.

The National Disaster Management Agency, or BNPB, said at least one person, a 70-year-old woman in Manado, died when part of a building collapsed. Several other people were injured in Manado and Ternate, according to local authorities. By Friday, preliminary BNPB tallies counted about 190 houses damaged and 355 people displaced in the two provinces.

Photos from Manado showed cracked facades and fallen masonry, including significant damage to a building used by the National Sports Committee. In the outskirts, families picked through debris and inspected walls for fresh fissures before returning indoors amid continuing aftershocks.

In North Maluku, the provincial government reported damage in Pulau Batang Dua, an island district administratively part of Ternate but several hours by boat from the main city. At least five houses there were heavily damaged and more than a dozen others lightly damaged, along with several churches.

One of the worst-hit structures was Gereja Kalvari, a prominent local church. Images shared by local media showed collapsed sections of its walls and large cracks running through the sanctuary, a stark blow in a community where religious buildings often serve as gathering points and informal shelters.

“The safety of the people is the main priority,” Coordinating Minister for Human Development and Culture Pratikno said in a statement released by the presidential palace. “Do not underestimate every second of early-warning information; all actions must be based on BMKG’s science.”

BNPB chief Lt. Gen. Suharyanto said preliminary data “record one fatality and a number of buildings affected by the quake,” adding that teams were still verifying damage, especially in remote island communities. He said President Prabowo Subianto had instructed him to travel to the affected region and oversee emergency operations, including ensuring food, water, temporary shelter and medical care for displaced residents.

Provincial officials in North Maluku said the situation was “gradually under control” and that boats had begun delivering food, tents and basic supplies to Batang Dua. In North Sulawesi, local governments ordered rapid inspections of schools, churches, sports facilities and hospitals for structural safety.

By Thursday afternoon, most ports, roads and communication lines in the region were functioning, and there were no widespread reports of long-term power outages.

A familiar hazard in the Ring of Fire

The earthquake struck in one of the world’s most seismically active regions. Indonesia sits atop the Pacific “Ring of Fire,” where several tectonic plates converge. The Molucca Sea, wedged between the arms of Sulawesi and the island of Halmahera, is a particularly complex zone, with multiple plates subducting beneath one another and frequent large earthquakes.

Some of Indonesia’s deadliest disasters have been triggered by similar undersea ruptures. The 2004 earthquake off Aceh, on Sumatra’s northern tip, sent a tsunami racing across the Indian Ocean that killed about 230,000 people in more than a dozen countries. In 2018, a magnitude 7.5 quake near Palu, in Central Sulawesi, produced a tsunami and soil liquefaction that killed more than 4,300 people. That event exposed weaknesses in early-warning procedures and public communication.

This time, BMKG has emphasized how quickly its systems moved.

Faisal said the agency met its target to issue an initial warning in under three minutes, then updated its analysis within the first hour and officially ended the tsunami alert once observations confirmed only minor sea-level changes. He urged residents to rely on official channels during such crises.

“We urge the public not to believe hoaxes,” he said. “Ensure information only comes from BMKG.”

The quake also rippled through Indonesia’s social media networks, where users posted videos of swaying light fixtures, cracked walls and long lines of vehicles heading uphill. Others debated shifting magnitude estimates and shared unverified rumors about additional waves, underscoring the challenge for authorities trying to keep pace with rapidly spreading information and misinformation.

While the April 2 quake was large in magnitude, seismologists say several factors likely limited its impact, including its depth, the details of how the fault ruptured and the way local underwater topography shaped the resulting waves. But they also caution that the same tectonic setting is capable of producing more damaging events.

As aftershocks continued to rattle the region, many residents in coastal neighborhoods spent the night in tents, community halls or on higher ground rather than return immediately to their homes.

By Friday, some had begun to drift back, collecting belongings and sweeping up glass. In Manado and Ternate, children pointed at fresh cracks spidering across living room walls. On Batang Dua, worshippers gathered outside the damaged Gereja Kalvari to pray.

The sea, which many had watched nervously hours earlier, lay flat and blue again. But phones buzzed with new alerts about aftershocks—a reminder that along the Molucca Sea, the calm between quakes is rarely more than temporary.