The team travelled north from Palu today, along the west side of the bay through the Donggala regency. First stop was the tourist site Tanjung Karang at the most northerly point of the promontory. There was very little evidence of tsunami inundation, except for a line of debris on the beach close to what looked like an earlier failure of an old seawall. Eye witnesses reported seeing three successive waves travelling south to the bay, though the inundation in the car park next to the beach was only ankle deep.
Returning southwards towards Palu, the Team observed very little damage due to ground shaking in non-engineered structures. The ground shaking damage started to become more noticeable only south of Lolidondo, where the Team stopped to investigate damage to two schools. These schools, constructed of confined masonry, had been closed due to extensive cracks in walls and one due to differential displacement of its foundation.
Evidence of coastal area liquefaction was also seen by the team. A significant example included the “sunken city” at Donggala port, where buildings sited on reclaimed land experienced settlement and tilting, and large portions of the port area were missing entirely. The latter likely due to flow liquefaction failure of the reclaimed land fill material with subsequent sliding into the sea.
Along the coast, further symptoms of liquefaction were seen, most significantly around the sea walls at Donggala Kota Wisata, where significant seawards displacements had occurred, possibly in the gravelly sand beneath the walls.
Further down the coast, at Loli Tasiburi eyewitnesses reported seeing soil bubbling and water spouting from the ground before a large area of land detached from the coastline. The behaviour of the water following the largest earthquake on 28 September provided the motivation for residents to flee inland, up the steep slope behind the beach. “Tasiburi” means “black sand” in the Kaili dialect, and this describes the soil seen here very well.
Tsunami damage was evident along most of the coastline, with increasing severity southwards towards Palu. This damage did not extend greatly inland (< 100 m), with indicative inundation heights up to 2.5 m. Low lying non-engineered structures suffered worst, many of these being washed away from their foundations. Most of the structures were non-engineered (either confined masonry or timber frame 1 storey buildings) and in low-lying areas suffered the collapse of external walls or were washed away from their foundations.
Finally, at Watusanpu Naval Base several boats were left high and dry by the tsunami, though didn’t travel very far inland due to the fairly steep topography.