Magnitude 6.2 quake off Pacitan rattles Java, exposes lingering risks on megathrust

A midnight jolt across southern Java

In the first minutes after 1 a.m. Friday, ceilings cracked and roof tiles clattered to the floor as people in Pacitan, Yogyakarta and dozens of towns across Java jolted awake. Many ran barefoot into the street or toward nearby hills, fearing not only the shaking underfoot but the possibility of a wave they could not see.

A magnitude 6.2 earthquake struck offshore Pacitan, East Java, at 1:06 a.m. local time on Feb. 6, killing one person, injuring at least 47, and damaging scores of buildings across three provinces. The quake was strong enough to be widely felt but, crucially, not powerful enough to generate a tsunami along one of the world’s most dangerous subduction zones.

Indonesia’s Meteorology, Climatology and Geophysics Agency (BMKG) classified the event as a megathrust earthquake on the plate boundary south of Java. Within minutes, the agency issued an information bulletin revising the magnitude from 6.4 to 6.2 and stressing that its modeling showed the quake “does not have tsunami potential.”

The reassurance came as millions reached for their phones in the dark. For coastal communities facing the Indian Ocean, the question was not abstract. Southern Java has lived through destructive tsunami earthquakes in 1994 and 2006 that together killed hundreds of people.

What happened offshore Pacitan

The main shock struck at 18:06:10 UTC on Feb. 5, or 1:06 a.m. Feb. 6 in western Indonesia time. BMKG located the epicenter roughly 89 kilometers south-southeast of Pacitan Regency, off East Java’s southern coast, at a depth of about 58 kilometers.

The U.S. Geological Survey recorded the quake at magnitude 5.8 with a depth near 40 kilometers, a difference seismologists say can reflect the use of different magnitude scales and data sets.

BMKG’s intensity map showed shaking at Modified Mercalli intensity IV—light to moderate shaking that can rattle dishes and crack weak plaster—in Pacitan as well as Bantul and Sleman regencies in the neighboring Yogyakarta Special Region. Intensity III shaking was reported across a wide swath of southern and central Java, including Trenggalek, Malang, Blitar, Surakarta, Wonogiri and Magelang. Lighter tremors reached the island’s north coast, including Tuban and Jepara.

Residents reported being woken from sleep in major urban centers including Yogyakarta and Malang, and some stayed outside for hours amid early aftershocks.

BMKG initially reported no aftershocks in the half-hour after the main quake, but later monitoring detected more than 20 smaller events, mostly between magnitudes 2.5 and 4.8, in the first 90 minutes. By Feb. 7, the agency said aftershock activity had begun to taper off and urged residents to remain calm but avoid damaged buildings.

One death, dozens injured

Local authorities reported one fatality tied to the quake in Ngadirojo District, Pacitan. An adult resident died after collapsing while attempting to evacuate. Officials said the person had a history of hypertension and suggested the death was linked to shock and underlying health conditions rather than direct building collapse.

In the Yogyakarta region, at least 47 people were injured, according to the provincial disaster management agency. Most of the injuries were reported in Bantul Regency, just south of Yogyakarta city, and were caused by falls during evacuation or by falling debris such as ceiling panels and roof tiles.

“People were startled and rushed outside. Some slipped on stairs; others were hit by parts of the building,” a Bantul disaster official said. Most of the wounded suffered minor to moderate injuries and were treated at local health facilities.

Damage from Pacitan to Bantul

Damage assessments continued through the weekend as local teams moved from village to village.

In Pacitan, initial reports listed around a dozen damaged houses. As inspectors reached more neighborhoods, the count grew to more than 40 structures, including residences, schools, places of worship and public facilities. Typical damage included collapsed or partially collapsed kitchens, cracked masonry walls and dislodged clay roof tiles, particularly in older or non-engineered buildings.

“Our data on damaged buildings is still temporary,” a Pacitan disaster official said as the first lists were released. “As reports come in from the field, these numbers will likely increase.”

In East Java’s Trenggalek Regency, authorities reported at least eight damaged buildings, including seven houses and a village hall. In Ponorogo, at least four homes collapsed and a mosque was damaged. In and around Blitar, local media documented an old house collapsing onto a nearby café and several homes with severely cracked walls or damaged roofs.

The Yogyakarta region, which sits inland but has a long memory of seismic disasters, also saw notable structural damage. The Bantul disaster agency identified at least 20 “damage points,” including 11 houses, two places of worship, four government offices, a Red Cross parking facility, two schools and a health facility. One of the worst-hit buildings was the Bantul Samsat office, where parts of the ceiling and interior walls fell.

In Yogyakarta city, at least two houses reported roof and ceiling damage. In Central Java’s Karanganyar Regency, officials said three houses and one school were affected, while Wonogiri recorded damage to at least one home.

A composite of local and national figures put the number of damaged buildings at no fewer than 69 across East Java, Yogyakarta and Central Java, a total that may rise as more remote areas are inspected.

A megathrust flexes—without a tsunami

BMKG said analysis of seismic waveforms showed the Pacitan event was a thrust-fault earthquake on the interface where the Australian Plate is subducting beneath the Sunda Plate along the Java Trench.

“This earthquake is a shallow tectonic event due to plate subduction and has a thrust mechanism,” BMKG said in a Feb. 6 statement.

Daryono, head of BMKG’s Earthquake and Tsunami Center, described it as a megathrust quake, using the term commonly applied to the largest subduction-zone earthquakes worldwide. He said the magnitude and depth in this case were below levels that typically generate significant tsunamis on that segment of the trench.

“If the magnitude had reached around 7.0, then a tsunami could have occurred,” Daryono told Indonesian media, warning that the region must not be complacent about the potential for larger events.

The quake occurred along the same broad plate boundary that produced a tsunami earthquake off East Java in 1994, when waves between 1 and 14 meters high killed more than 200 people, and another tsunami off West and Central Java in 2006 that sent waves up to 21 meters and left hundreds dead.

Those memories help explain why many residents near the south coast reported self-evacuating to higher ground, even as BMKG repeated that the Pacitan quake did not have tsunami potential and did not trigger a formal tsunami warning.

Disaster readiness under scrutiny

Indonesia’s National Disaster Management Agency (BNPB) said it had stepped up coordination with provincial and local governments following the quake.

“BNPB is intensifying coordination so that the impacts of the Pacitan earthquake can be handled quickly and appropriately,” agency spokesperson Abdul Muhari said. He said BNPB was supporting local disaster offices—known as BPBDs—in deploying rapid assessment teams and strengthening on-the-ground command systems.

Pacitan, Bantul and neighboring regencies activated their BPBD units, dispatched teams to map damage and needs, and advised residents to avoid entering visibly cracked or partially collapsed structures.

The response is the latest test of Indonesia’s disaster management architecture, built up in the wake of the 2004 Indian Ocean tsunami and codified in Law No. 24 of 2007 on Disaster Management. That law created BNPB and mandated the establishment of local BPBDs across the country. It also underpins the operation of the Indonesian Tsunami Early Warning System (InaTEWS), which BMKG runs with support from domestic and international partners.

Officials and researchers have credited these reforms with improving early warning and coordination, but the Pacitan quake highlighted persistent vulnerabilities, particularly in the building stock of rural Java. Damage was concentrated in older brick houses and public buildings with heavy roofs and limited reinforcement—a pattern seen repeatedly in past earthquakes.

Living on the edge of a major fault

Pacitan Regency, with a population of nearly 600,000 and a coastline of beaches and fishing villages facing the Indian Ocean, sits directly opposite the Java trench. So do densely populated parts of Yogyakarta and Central Java. The subduction zone offshore is thought to be capable of earthquakes as large as magnitude 8.5 or more.

BMKG and other agencies have long urged regular earthquake and tsunami drills, especially in schools and coastal communities, and pressed for stronger enforcement of building standards. The government has modernized warning systems, but many homes and smaller public facilities remain vulnerable to shaking.

For families whose houses cracked in Ngadirojo, Ponorogo or Bantul, the Pacitan quake will mean weeks or months of repairs and reconstruction, often with limited insurance or savings. For seismologists and disaster managers, it is a data point and a warning.

The difference between this event and the catastrophes of 1994 and 2006 was, in part, a matter of numbers on the magnitude scale. The ground under Java’s south coast shifted, but not quite enough to send a wall of water ashore.

How communities and authorities use this near-miss—to reinforce trust in official warnings, retrofit weak structures and rehearse for a larger emergency—may help determine the outcome when the subduction zone next unleashes its full force.