Surface ruptures of the 29 September 2018 earthquake (Mw7.4) on the Palukoro major strike-slip fault in Central Sulawesi, Indonesia
Abstract
The Mw7.4 Earthquake in Central Sulawesi ruptured two major segments connected by a 6-km wide releasing step of the left-lateral Palukoro Fault, hence exceeding the maximum 4-km width of step over that prohibit rupture propagation (Wesnousky, 2006). The movement occurred largely on a single major line, observed from Palu beach runs to the south for 70 km long. The offsets are clearly seen when surface ruptures crossing and displaced many artificial features including asphalt roads, pavements between houses, displaced buildings, fences as well as alignments in rice field. For the first 20-km from Palu beach southward, the left-lateral offset varies between 350 to 480 cm. Then 15-km to south, it gradually decreases to 150 cm and turn into a 12-km wide zone of normal faulting and ground wrapping toward the major normal fault showing a vertical movement of more than 5 m at the west end of the releasing step. The releasing-step shows a combination of left-lateral and normal faults. At east-end corner, it displays a wide zone of normal faults with total movement of 1.9 m. South of it on Saluki segment, surface ruptures shows a 3.2-m left lateral slip. 20 km southward, it gradually decreases to less than 10 cm before ruptures disappears. North from Palu beach, the ruptures continue underwater along the fault line, shown on bathymetry data for 70 km or so. However, we observe surface ruptures inland, across the bay, but with predominantly normal faulting, interpreted as a fault branch. There is also a push-up structure accommodated by a predominantly reverse fault that runs through the collapsed large bridge construction, a few hundred meters east of the main strike-slip fault line. North of the east-end of the releasing step, we observe a wide fracture zone, as a series of normal fault, open fractures and linear grabens, appears to be an extension of the Saluki segment. It is coupled with ground wrapping associated with liquefaction and land movements. The northern tip of the fracture zone abuts on the largest land slide and liquefaction that swallowed the Petobo residential houses next to the airport. 5-km to south, in Jono-Oge, the fracture-wrapped zone cut by the wide channel of mud flow. Across the mud flow at the southern-end, the fracture zone abuts on another large liquefied-land movement at Sibalaya.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMNH22B..03N
- Keywords:
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- 4313 Extreme events;
- NATURAL HAZARDSDE: 4315 Monitoring;
- forecasting;
- prediction;
- NATURAL HAZARDSDE: 4341 Early warning systems;
- NATURAL HAZARDSDE: 4564 Tsunamis and storm surges;
- OCEANOGRAPHY: PHYSICAL