Forensic investigation of flowslides triggered by the 2018 Sulawesi earthquake

Abstract

The Sulawesi earthquake with a moment magnitude of Mw 7.5 struck the Central Sulawesi region of the Sulawesi Island, Indonesia, on September 28, 2018. The epicenter of the earthquake was located in the mountainous region of Donggala Regency, in the neck of the Minahasa Peninsula in the Central Sulawesi Province of Indonesia. Although the epicenter was located in Donggala Regency, the greatest devastating effects were observed about 70 km south of the epicenter in the Palu Valley. The event was the first of its kind to cause large-scale flowslides simultaneously at four key locations such as Balaroa, Petobo, Jono Oge, and Sibalaya with extensive ground displacements ranging from several hundred meters to more than 1 km. This article reviews the field observations of geotechnical failures and infrastructure damage caused by liquefaction resulting from the shallow strike-slip earthquake at Palu City, Donggala Regency, and Sigi Regency. A geo-spatial analysis was performed on data collected from aerial drone imagery, along with portable dynamic cone penetration testing (PDCPT) in the field. The investigation revealed a highly stratified ground with alternating soil layers of varying permeability and very low bearing resistance at shallow depths. The investigation also helped in assessing the extent of damage caused by geotechnical failure to the residential infrastructures, irrigation structures, and roads. Graphical Abstract

Diversity and Benefits of Asteraceae in Kapopo Ngatabaru Great Forest Park

“…Alluvium and coastal deposit layers are composed of gravel, sand, mud, and coral limestone, which were formed in river, delta, and shallow sea environments that are Holocene in age. The metamorphic rock complex layer is composed of amphibolite schist, schist, genes, and marble, which has an age ranging from Palaeozoic to pre-Tertiary [16]. Based on the results of exploration on the hiking trails in Kapopo Ngatabaru Great Forest Park, five species were obtained from the Family Asteraceae: Chromolaena odorata, Porophyllum ruderale, Eleutheranthera ruderalis, Synedrella nodiflora, and Tridax procumbens.…”

Long-lasting Post-quake Deformation Buildups in the Grounds that Spread Laterally in Recent Earthquakes

“…This earthquake's most spectacular and devastating aspect was lateral slides of the almost flat alluvial soil deposit along the west and east bounds of the basin. Lateral spreads were the most serious in Balaroa, Petobo, Jono Oge, and Sibalaya (Rohit et al 2021;Kiyota et al 2020). The maximum flow distance at each site was reportedly several hundred meters or more.…”

“…Various theories for lateral-spread initiations and motions are discussed by many researchers (Kiyota et al 2020;Rohit et al 2021). They have a common opinion that liquefiable deposits and multiple capping layers might have triggered the flow slides.…”

Forensic assessment of landslides induced by environmental changes in Sumedang, Indonesia, an important step for the future disaster prevention

“…A forensic landslide involves some analysis from geology and environmental point of view, which is crucial to determining the cause of a landslide event. Landslide forensic investigations have been carried out previously, for example, in the investigations of flowslides caused by the Sulawesi earthquake [18], in the forensic analysis and numerical simulation of a catastrophic landslide of underground mining in a mountainous area of southwestern China [19], and in the forensic investigation of a backyard landslide with a sewer in Bethel Park, Pennsylvania [20]. The principle of forensic landslide is to look backward in space and time before the landslide occurred.…”