EXPLAINER: Why is Indonesia’s light wave so deadly? ( News Washington )


JAKARTA, Indonesia — A massive earthquake has left more than 260 dead and hundreds injured as buildings collapsed and terrified residents ran for their lives on Indonesia’s main island of Java.

Bodies were pulled from the wreckage on Tuesday morning in the hard-hit city of Cianjur, located in the country’s most populous West Java province and some 217 kilometers (135 miles) south of the capital city of Batavia. Many are still missing.

While the magnitude would typically be expected to cause minor damage to buildings and other structures, experts say the proximity to fault lines, low shaking and inadequate infrastructure all contributed to the earthquake’s inability to withstand the damage.

Here I look more closely at the earthquake and the reasons why it brought so much devastation;


The US Geological Survey said the quake measured late Monday afternoon at a magnitude of 5.6 and struck at a depth of 10 kilometers (6.2 miles).

A movement of this magnitude usually does not cause extensive damage to well-built infrastructure. But the agency points out, “there is not one size above which damage can occur. It depends on other variables, such as the distance from the earthquake, what type of land you are in, the construction of the building” and others.

Dozens of buildings in Indonesia were damaged, including Islamic boarding schools, hospitals and other public facilities. Roads and bridges were also damaged, and parts of the country experienced power blackouts.


Experts said the proximity of the fault line, the height of the tremors and buildings not constructed using earthquake-proof methods were factors in the devastation.

“Although the earthquake was of medium size, it was located near the surface … and inland, close to where people live,” said Gayatri Marliyani, assistant professor of geology at Gadjah Mada University, in Yogyakarta, Indonesia. “The force was still great enough to cause a significant shock that led to the damage.”

The worst affected area is close to many known faults, Marliyani said.

A fault is a place in a long broken rock that forms the surface of the earth. But when an earthquake occurs in one of these faults, the rock of fault slides from one side in relation to the other.

“The area probably has inland faults compared to other parts of Java,” said Marliyani.

He also added that while some faults are well known in the area, there are many other active faults that are not well studied.

Many buildings in the region were also built without proof of design, which contributed to further damage, said Danny Hilman Natawidjaja, an earthquake geology expert at the Indonesian Geotechnology Sciences Institute Research Center.

“This move is even more destructive in scale and depth,” he said.

Does INDONESIA usually have earthquakes?

The region of more than 270 million people is often hit by earthquakes, volcanic eruptions and tsunamis due to its location on an arc of volcanoes and a fault line in the Pacific Basin known as the “Ring of Fire”. The palm area is some 40,000 kilometers (25,000 miles) wide and is where most earthquakes occur.

Many of Indonesia’s earthquakes are minor and cause little damage. But there were also earthquakes.

In February, a magnitude 6.2 earthquake killed at least 25 people and injured more than 460 in West Sumatra province. In January 2021, a magnitude 6.2 earthquake killed more than 100 people and injured nearly 6,500 in the province of West Sulawesi.

The powerful Indian Ocean earthquake and tsunami in 2004 killed 230,000 people in twelve countries, most of them in Indonesia.

The Associated Health and Science Press Department receives support from the Howard Hughes Medical Science Education Institute. AP is solely responsible for all content.


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