Pakar LIPI Merinci Fenomena Alam 'Likuifaksi' Di Palu

Summary

The video discusses the phenomenon of liquefaction that occurred after a 7.4 magnitude earthquake and tsunami in Palu, Central Sulawesi, in September 2018. Liquefaction, where solid ground turns into mud, engulfed buildings and trees. The video explains how this phenomenon occurs, particularly in areas with loose, water-saturated soil. Experts also highlight that such events can be predicted through soil tests. The phenomenon, which causes significant damage, was observed in multiple areas, including Petobo and Balaroa, where hundreds of homes were buried under mud. This discussion emphasizes the need for awareness and preparedness for such natural disasters.

Takeaways

• 😀 The 7.4 magnitude earthquake in Palu, Sulawesi Tengah, caused a phenomenon known as liquefaction, where the ground turned into mud, swallowing buildings and trees.
• 😀 Liquefaction occurs when saturated ground loses its strength and behaves like a liquid, making it unable to support the weight of structures on top.
• 😀 Liquefaction typically happens in areas with loose, sandy soils that are poorly compacted, which allow groundwater to change the soil's consistency during an earthquake.
• 😀 The 2018 earthquake in Palu triggered massive liquefaction, with entire neighborhoods, like Desa Jono Oge, experiencing buildings and trees being swallowed by the shifting ground.
• 😀 The process of liquefaction involves solid soil turning into slurry-like mud that moves slowly, causing structures to appear as if they are sinking.
• 😀 The presence of shallow groundwater and loose soil conditions can make areas more prone to liquefaction, with the ground losing its ability to hold up structures.
• 😀 Standard penetration tests and other geotechnical assessments can help predict the likelihood of liquefaction in certain areas by studying soil composition and water tables.
• 😀 Liquefaction was not a post-earthquake event but happened during the earthquake itself, due to the powerful shaking causing the ground to lose its structural integrity.
• 😀 Areas with loose soil and shallow groundwater, like those around Palu, were especially vulnerable to liquefaction, even if they were far from the epicenter of the quake.
• 😀 Scientists have developed predictive maps based on past studies, such as one in Padang, which showed how liquefaction was expected in specific coastal areas during a previous earthquake in 2009.

Q & A

What is liquefaction and how does it relate to the earthquake in Central Sulawesi?

Liquefaction is a phenomenon where solid ground saturated with water behaves like a liquid during an earthquake. In the case of the earthquake in Central Sulawesi, the shaking caused the soil to lose its strength and behave like quicksand, swallowing buildings and trees.

How did liquefaction manifest in Palu, Central Sulawesi after the earthquake?

In Palu, after the earthquake of magnitude 7.4, liquefaction occurred in several areas, particularly in Desa Jono Oge. The ground, which was originally solid, turned into a muddy liquid, swallowing buildings and trees. The soil lost its ability to support the weight of structures on top of it.

What is the role of water in the process of liquefaction?

Water plays a crucial role in liquefaction. When the soil is saturated with water and subjected to strong shaking, it loses its strength and behaves like a fluid, causing the ground to collapse or shift, which leads to the destruction of buildings and other structures.

What factors contribute to the occurrence of liquefaction during an earthquake?

Liquefaction is more likely to occur in areas with loose, unconsolidated sandy soils that are saturated with water. The depth of the groundwater also plays a role—if the groundwater table is shallow, liquefaction is more likely to happen when strong shaking occurs.

How can we predict areas at risk for liquefaction before an earthquake occurs?

Liquefaction potential can be assessed using various geotechnical tests, such as Standard Penetration Tests (SPT), Cone Penetration Tests (CPT), and shear wave velocity measurements. These tests help determine the density and water content of the soil, which are key factors in liquefaction risk.

What scientific method was used to predict liquefaction in Padang in 2009?

In Padang, a detailed study between 2006 and 2013 produced a map that accurately predicted areas at risk of liquefaction during the 2009 earthquake. This map was based on an analysis of soil composition, water levels, and past earthquake data.

What is the relationship between earthquake duration and liquefaction risk?

The duration of an earthquake is critical for liquefaction to occur. Strong shaking for more than one minute increases the likelihood of liquefaction, as it allows the soil to lose its strength and behave like a fluid. Shorter tremors may not have the same effect.

Can liquefaction occur in areas far from the earthquake epicenter?

Yes, liquefaction can occur far from the earthquake's epicenter, especially in areas with soft, loose soils. The seismic waves from the earthquake can travel great distances, and if the ground conditions are right, liquefaction can still occur.

What are the different manifestations of liquefaction, apart from ground subsidence?

Liquefaction can also manifest as sand boils or eruptions, where pressurized water forces sand and mud to the surface. Additionally, it can cause the ground to shift, creating waves on the surface or causing buildings to tilt or collapse.

What should be done to mitigate the risks of liquefaction in vulnerable areas?

To mitigate liquefaction risks, it is crucial to avoid constructing buildings on loose, water-saturated soils. Local governments should use geotechnical studies to identify high-risk areas and implement land-use policies that prevent construction in those zones. For areas already built upon, retrofitting buildings and improving soil stability are essential.