Why do major earthquakes keep happening in Lombok recently?

Lombok’s Earthquake Problem: Why the Ground Keeps Shaking

Lombok. It’s a beautiful island, no doubt. But lately, it seems like the ground is always rumbling. What’s the deal? Why does Lombok keep getting hit by these major earthquakes? Well, the answer, unfortunately, lies beneath our feet – in the island’s tricky tectonic situation.

Think of Indonesia as a whole as a seismic hot zone. It’s smack-dab in the middle of the Pacific Ring of Fire, famous (or maybe infamous) for its volcanoes and earthquakes. Now, zoom in on Lombok. This island sits right on top of a place where two massive tectonic plates are going head to head i. The Australian Plate is diving, or subducting, under the Sunda Plate (which is part of the Eurasian Plate). This isn’t a gentle process – it’s more like a slow-motion car crash.

These plates grind against each other with incredible force, building up stress over time i. Imagine bending a stick further and further – eventually, it’s going to snap. That’s what happens here, but on a much grander scale. When that built-up stress finally releases, BAM! Earthquake i. And that’s the story of many of Lombok’s tremors.

But wait, there’s more! Lombok also has the dubious honor of being near something called the Flores Back Arc Thrust (FBT). Try saying that five times fast! Basically, it’s a zone of faults north of the island ii. The FBT is a result of the Australian continental crust colliding with the Sunda Plate ii. This collision has led to back-arc thrusting, where the crust is starting to ride over the top of the Sunda Plate ii. The 2018 Lombok earthquake sequence has been associated with ruptures along the Flores Thrust ii. Source models suggest that the Lombok sequence may have ruptured the Flores thrust ii.

Remember those awful earthquakes in 2018? Those weren’t just a one-off. It was a whole series of quakes that just kept coming iii. It started with a jolt on July 29th, a magnitude 6.4 foreshock that was a warning sign of what was to come iii. Then, on August 5th, the big one hit: a magnitude 6.9 earthquake that really shook things up iii. And the aftershocks? They just kept on rattling the island, with more significant events on August 9th and August 19th iii. It was a truly terrifying time.

What made those earthquakes even worse was how shallow they were iii. The source of the earthquake, or hypocenter, was less than 25 km below the surface iii. The closer an earthquake is to the surface, the more damage it causes. It’s like dropping something heavy from a small height vs a large height. The result? Landslides, buildings collapsing, and even a small tsunami iii. The final toll was heartbreaking: over 500 lives lost, countless injuries, and hundreds of thousands of people displaced iii.

Why did we see so many earthquakes in such a short period? Well, scientists are still piecing it together, but the initial quake may have triggered the others iii. It’s like dominoes falling, one setting off the next. The initial earthquake may have altered the stress state in the hypocenter location of the subsequent event, precipitating the coseismic failure iii. The relocated aftershocks of the 2018 sequence show that the magnitude 7.0 and 6.9 earthquakes ruptured two different regions iii. The magnitude 7.0 earthquake propagated westward, while the magnitude 6.9 earthquake propagated eastward iii.

Sadly, it’s not just the tectonic plates that are to blame. Other factors make things even worse in Lombok. For starters, building codes aren’t always up to par, and construction practices can be pretty shaky iv. Many buildings just aren’t built to withstand strong earthquakes, which is why they crumble so easily iv. Poverty also plays a role, making it tough for communities to invest in stronger buildings and prepare for disasters iv. And let’s not forget the ever-present threat of tsunamis, which Lombok is vulnerable to iv.

So, what’s the outlook for the future? Unfortunately, Lombok will continue to experience earthquakes. It’s just the nature of the beast, given its location i. While we can’t predict exactly when the next big one will hit, we can definitely take steps to be better prepared. That means stricter building codes, educating people about earthquake safety, improving tsunami warning systems, and empowering communities to create their own disaster plans iv.

Lombok is a special place, and its people deserve to feel safe. By understanding why these earthquakes happen and taking action to mitigate their impact, we can help build a more resilient future for this beautiful island. It won’t be easy, but it’s absolutely essential.