Story highlights Geologists say an even larger quake in the region is lurking

Scientist: "We do not know when it's going to occur"

Chile has seen no shortage of seismic activity in recent years

This one was big but it's not the Big One.

An 8.2-magnitude earthquake struck off the coast of northern Chile Tuesday night, triggering small landslides, setting off a tsunami and killing at least five people.

But geologists say an even larger quake in the region is lurking.

"This magnitude 8.2 is not the large earthquake that we were expecting in this area," said Mark Simons, a geophysicist at Caltech in Pasadena, California. "We're expecting a potentially even larger earthquake."

Photos: Photos: Earthquake off Chilean coast Photos: Photos: Earthquake off Chilean coast Earthquake off Chilean coast – Heavy machinery is used to clear debris on the road leading to the town of Camarones, Chile, on Thursday, April 3. Access to the town was cut off when an 8.2-magnitude earthquake struck northern Chile on April 1. Hide Caption 1 of 24 Photos: Photos: Earthquake off Chilean coast Earthquake off Chilean coast – People take shelter under a tent after they left their homes in Alto Hospicio, Chile, on April 3. Hide Caption 2 of 24 Photos: Photos: Earthquake off Chilean coast Earthquake off Chilean coast – Chilean soldiers stand guard at a supermarket as people wait in line to buy supplies in Iquique, Chile, on April 3. Hide Caption 3 of 24 Photos: Photos: Earthquake off Chilean coast Earthquake off Chilean coast – Soldiers patrol inside a mall in Iquique on April 3. Hide Caption 4 of 24 Photos: Photos: Earthquake off Chilean coast Earthquake off Chilean coast – People walk along a cracked road in Iquique on Wednesday, April 2. Hide Caption 5 of 24 Photos: Photos: Earthquake off Chilean coast Earthquake off Chilean coast – Fishing boats washed ashore by a tsunami sit in the waters of Iquique on April 2. Hide Caption 6 of 24 Photos: Photos: Earthquake off Chilean coast Earthquake off Chilean coast – Rescue personnel get ready to go into action April 2 in Iquique. More than 2,500 homes sustained serious structural damage in the region around the northern port city, an official said. Hide Caption 7 of 24 Photos: Photos: Earthquake off Chilean coast Earthquake off Chilean coast – A chair floats in a flooded area of Iquique on April 2. Hide Caption 8 of 24 Photos: Photos: Earthquake off Chilean coast Earthquake off Chilean coast – People wait at the Arturo Merino Benitez Airport in Santiago, Chile, on April 2 as flights are canceled because of the earthquake. Hide Caption 9 of 24 Photos: Photos: Earthquake off Chilean coast Earthquake off Chilean coast – Fishing boats lie in the waters of Iquique on April 2. Hide Caption 10 of 24 Photos: Photos: Earthquake off Chilean coast Earthquake off Chilean coast – Chilean President Michelle Bachelet speaks in Santiago on April 2. Hide Caption 11 of 24 Photos: Photos: Earthquake off Chilean coast Earthquake off Chilean coast – A man waits for medical treatment at an emergency center in Iquique on April 2. Hide Caption 12 of 24 Photos: Photos: Earthquake off Chilean coast Earthquake off Chilean coast – People stay on a beach in Arica, Chile, after the earthquake struck. The quake generated tsunami waves of more than 6 feet on the coast of Pisagua, according to the Pacific Tsunami Watch Center. Iquique saw 7-foot waves. Hide Caption 13 of 24 Photos: Photos: Earthquake off Chilean coast Earthquake off Chilean coast – A military vehicle patrols the streets of Iquique on April 1. Chile is on the "Ring of Fire," an arc of volcanoes and fault lines that circles the Pacific Basin and is prone to frequent earthquakes and volcanic eruptions. Hide Caption 14 of 24 Photos: Photos: Earthquake off Chilean coast Earthquake off Chilean coast – People embrace on the upper floor of an apartment building in Iquique on April 1. Hide Caption 15 of 24 Photos: Photos: Earthquake off Chilean coast Earthquake off Chilean coast – A view of Iquique following the earthquake on April 1. Hide Caption 16 of 24 Photos: Photos: Earthquake off Chilean coast Earthquake off Chilean coast – People evacuate Iquique on April 1. Hide Caption 17 of 24 Photos: Photos: Earthquake off Chilean coast Earthquake off Chilean coast – People take to the streets after the earthquake, which hit at 6:46 p.m. local time. Hide Caption 18 of 24 Photos: Photos: Earthquake off Chilean coast Earthquake off Chilean coast – A fire burns at a restaurant in Iquique after the earthquake. Hide Caption 19 of 24 Photos: Photos: Earthquake off Chilean coast Earthquake off Chilean coast – A woman and her dog stand against a wall in Iquique on April 1. Hide Caption 20 of 24 Photos: Photos: Earthquake off Chilean coast Earthquake off Chilean coast – Girls wait in a hallway before evacuating Iquique on April 1. Hide Caption 21 of 24 Photos: Photos: Earthquake off Chilean coast Earthquake off Chilean coast – Iquique residents wait outside on April 1. Hide Caption 22 of 24 Photos: Photos: Earthquake off Chilean coast Earthquake off Chilean coast – Iquique residents wait in a parking garage after the earthquake. Hide Caption 23 of 24 Photos: Photos: Earthquake off Chilean coast Earthquake off Chilean coast – Iquique residents prepare to leave their homes on April 1. Hide Caption 24 of 24

It could be tomorrow. Or it could be 50 years.

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"We do not know when it's going to occur," he said.

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Here's why:

Chile sits on an arc of volcanos and fault lines circling the Pacific Ocean known as the "Ring of Fire." This area sees frequent earthquakes and volcanic eruptions.

The country itself has seen no shortage of seismic activity in recent years.

Since 1973, Chile has had more than a dozen quakes of magnitude-7.0 and above.

In 2010, about 500 people died when an 8.8-magnitude earthquake hit. That quake was so violent, it moved one whole city about 10 feet west.

Simons says Tuesday's quake is of interest because the fault line along Chile's coast has constantly shifted during the last 140 years.

In recent weeks, this area has seen a cluster of activity-- something like 50 to 100 smaller quakes.

Then, late last month, a 6.7 and a 6.1 magnitude quake struck.

When quakes happen, the surface ruptures. The two sides of the fault slip past each other.

But the area to the north and south of Tuesday's quake "did not rupture in this event," Simons said. And it's "still an area that hasn't ruptured in 140-odd years."

Given that it's an area of frequent quakes, and frequent ruptures, it may only be a matter of time.

"We expect another 8.8-8.9 earthquake here sometime in the future," Simons said.

The good news? "It may not occur for many, many years."