Here’s why Lombok has so many earthquakes
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Here’s why Lombok has so many earthquakes

THE Indonesian island of Lombok has been hammered by a series of powerful earthquakes in the past three weeks that have killed more than 500 people and left hundreds of thousands homeless.

The latest big one came on Sunday when its 3.3 million residents were rocked by a string of tremors and aftershocks, with the strongest measuring 6.9-magnitude.

Weeks prior to that, tens of thousands of homes, mosques and businesses across Lombok had already been destroyed by an earlier 6.9-magnitude quake on August 5 that killed at least 481 people.

A week before that quake, a tremor surged through the island and killed 17.


So why is the idyllic island the site of such consistent volatility?

Why does Lombok have so many earthquakes?

Part of the Lesser Sunda island chain, Lombok is nestled in the Indonesian archipelago. The popular holiday destination of Bali is just 100km to the East across the Lombok Strait, and the lesser-known island of Sumbawa lies to the West.

The archipelago is known for its frequent earthquake activity, as it sits on the Ring of Fire, an area in the basin of the Pacific Ocean where major tectonic plates meet, making earthquakes and volcanic eruptions are rife.

SEE ALSO: Powerful quake kills scores, triggers panic on popular Indonesian island

The horseshoe-shaped line, measuring 40,000km long, is responsible for about 90 percent of earthquakes across the globe.

Lombok itself lies on top of the destructive plate boundary between the Australian Plate and the Sunda Plate.

The recent earthquakes are believed to be caused by the arc being pushed over the back-arc Bali Basin along a major thrust fault, called the Flores Thrust.


Why so many quakes recently?

Put simply, the seismic activity increased recently as different parts of the fault slipped and moved. Pinpointing exactly what is causing the current ruptures, however, is more difficult. It’s hard to say what’s going on beyond just that it shows an accumulation of stress and the boundary of the plates.

“The fault will move periodically when tension builds up,” Danny Hilman Natawidjaja, senior geologist at the Indonesian Institute of Sciences, told AFP.

SEE ALSO: How can Indonesia address its vulnerability to earthquakes?

Will there be more earthquakes?

Geologists at the University of Colorado warned in January that big quakes are going to be more frequent in the next few years because the earth’s spin has slowed – causing the planet’s “waist” to contract.

Since 2011, our planet has been rotating at a pace a few thousandths of a second slower than usual. As the equator shrinks during this time, it’s hard for the tectonic plates to adjust accordingly.

Instead of falling in line with the slimmer waistline, the edges of those plates get squeezed together.

This takes time for us to feel on the ground. But after five years without many high-intensity quakes, we’re approaching the moment when the effects of this squeeze could start to be felt around the globe, geologist Roger Bilham told  Business Insider.

For comparison, only seven earthquakes above a magnitude 7.0 were recorded in 2017.

Bilham predicts that we could see, on average, an incredible 20 high-magnitude earthquakes per year, between 2018 and 2021.

Sadly, it looks like Lombok’s troubles aren’t over yet.

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