Scientists have identified a potential tsunami risk in the region chosen by Indonesia for its new capital.
The researchers mapped evidence of multiple ancient underwater landslides in the Makassar Strait between the islands of Borneo and Sulawesi.
If the largest of these were repeated today, it would generate tsunami capable of inundating Balikpapan Bay – an area close to the proposed capital.
But the international team cautions against an overreaction.
“We still have a lot more work to do to properly assess the situation. That said, this is something that Indonesian governments probably should have on the risk register somewhere – even if we’re only talking about ‘low frequency, high impact’ events,” said Dr Uisdean Nicholson from Heriot-Watt University, UK.
His British-Indonesian research team used seismic data to investigate the sediments and their structure on the Makassar seafloor.
The survey revealed 19 distinct zones along the strait where mud, sand and silt have tumbled downslope into deeper waters.
Some of these slides involved hundreds of cubic kilometres of material – volumes that are more than capable of disturbing the water column, and of producing large waves at the sea surface.
Indonesia experienced two landslide-driven tsunami events in 2018 – when the side of the Anak Krakatau volcano collapsed and separately when a quake triggered slope failures in Sulawesi’s Palu Bay.
So awareness is certainly growing that tsunami can come from sources other than a seafloor megathrust earthquake like the one off Sumatra in 2004 which wreaked havoc right around the Indian Ocean.
President Joko Widodo announced last year that Indonesia would move its capital from Jakarta to Borneo.
The new administrative centre is to be built across two regencies – Kutai Kartanegara and North Penajam Paser – in East Kalimantan province, close to the existing cities of Balikpapan and Samarinda.
By Jonathan Amos | BBC World