Sulawesi earthquake and tsunami

Sulawesi earthquake and tsunami
Name	2018 Sulawesi earthquake and tsunami
Date	2018-09-28
Magnitude	7.5 M_w
Depth	10 km
Epicenter	Palu-Koro fault, Sulawesi, Indonesia
Affected	Sulawesi, Indonesia
Casualties	~4,300 dead, thousands injured and missing
Type	Strike-slip with complex tsunami generation

Sulawesi earthquake and tsunami was a combined seismic and oceanic disaster that struck the island of Sulawesi in Indonesia on 28 September 2018. The event produced a large, destructive tsunami and widespread structural collapse across the city of Palu, the Donggala Regency, and surrounding areas. The disaster drew international attention from organizations including the United Nations and humanitarian agencies such as the International Red Cross and Red Crescent Movement.

Background and tectonic setting

Sulawesi lies at the junction of the Eurasian Plate, the Australian Plate, and the complex microplates of the Philippine Sea Plate system, with the island crossed by several major fault zones including the Palukoro Fault, the Palu-Koro Fault, and the Molucca Sea Collision Zone. Regional seismicity is influenced by the Sunda Arc, the Celebes Sea margin, and interactions with the Pacific Plate subduction system. Historical events in the region include the 1927 Bali earthquake and sequences associated with the Jakarta Basin and Makassar Strait tectonics. The Palu-Koro Fault is a well-documented left-lateral strike-slip structure that had been studied by institutions such as the Geological Agency of Indonesia and university groups from Gadjah Mada University and Institut Teknologi Bandung.

Earthquake event

At 18:02 local time on 28 September 2018 a moment magnitude 7.5 earthquake ruptured along the northern segment of the Palu-Koro Fault, producing strong ground shaking felt across Central Sulawesi, West Sulawesi, and parts of North Sulawesi. Seismological analyses by organizations including the United States Geological Survey, the BMKG (Meteorology, Climatology, and Geophysical Agency of Indonesia), and researchers from Columbia University and University of Tokyo characterized the event as predominantly strike-slip with shallow hypocentral depth. The rupture generated complex surface offsets mapped by teams from NASA using synthetic-aperture radar and satellite imagery from Sentinel-1 and Landsat. Ground failures included widespread liquefaction in coastal plains near Palu Bay and lateral spreading observed near infrastructure such as the Trans-Sulawesi Highway and local bridges.

Tsunami occurrence and impact

A tsunami struck within minutes to an hour after the mainshock, inundating coastal communities around Palu Bay, Talise Beach, and the estuary of the Koro River. The tsunami's generation involved a combination of mechanisms debated by researchers from Monash University, King Abdullah University of Science and Technology, and the Indonesian Institute of Sciences (LIPI): coseismic displacement on the fault, submarine landslides on the continental slope of the Makassar Strait, and localized coastal subsidence. Large waves overwhelmed seawalls and coastal defenses at Pantai Talise and produced runups documented by teams from University of California, Berkeley and University of Bristol. The intensity of inundation was amplified by the funneling geometry of Palu Bay, a phenomenon also noted in historical tsunamis affecting Lafayette Bay-style embayments.

Casualties and damage

The combined earthquake, tsunami, and associated ground failure caused catastrophic damage to urban and rural areas. In Palu extensive collapse affected multi-story buildings such as hotels and apartment blocks, while the Mawar Hotel and local markets experienced severe structural failure. Infrastructure losses included damage to the Palu Airport, road networks connecting Donggala and Sigi Regency, and utilities serving hospitals like RS Anutapura Hospital. Casualties numbered in the thousands, with institutional tallies from Badan Nasional Penanggulangan Bencana and international agencies estimating approximately 4,300 dead and many more injured or missing. Cultural heritage sites and religious buildings, including mosques and churches across Central Sulawesi, sustained damage. Economic impacts affected fisheries in the Makassar Strait and disrupted supply chains linked to ports such as Pantoloan Harbor.

Response and recovery

Immediate response involved mobilization by the Indonesian National Armed Forces, the Indonesian National Police, local disaster agencies, and international partners including teams from Australia, Japan, and United States Agency for International Development (USAID). Search and rescue operations used assets from the BASARNAS organization, while relief coordination engaged the United Nations Office for the Coordination of Humanitarian Affairs and NGOs such as Médecins Sans Frontières and Save the Children. Aid delivered included medical assistance, temporary shelter, water purification systems, and emergency communications supported by satellite teams from Inmarsat and Iridium Communications. Longer-term recovery planning involved provincial authorities from Central Sulawesi Provincial Government and reconstruction frameworks referencing lessons from the 2004 Indian Ocean earthquake and tsunami and the 2011 Tōhoku earthquake and tsunami.

Investigation and scientific studies

Post-event investigations combined field surveying, geodetic measurements, and numerical modeling by consortia from University of Oxford, Massachusetts Institute of Technology, ETH Zurich, and Indonesian institutions. Studies evaluated the role of submarine landslides using bathymetry from GEBCO and modeling by teams at Scripps Institution of Oceanography and the National Oceanic and Atmospheric Administration. Research published in venues associated with Nature, Science Advances, and the Bulletin of the Seismological Society of America debated tsunami generation mechanisms and recommended improvements to early warning systems like the Indonesia Tsunami Early Warning System. Outcomes emphasized enhancing coastal zoning by provincial authorities, upgrading building codes influenced by SNI standards, and expanding international collaboration through entities such as the International Tsunami Information Center.

Category:2018 earthquakes Category:Earthquakes in Indonesia Category:Tsunamis in Indonesia