Turns out the temblor was a tsunami earthquake, an uncommon breed of slow, relatively mild quakes that produce massive tsunami waves.

Now, a new analysis of data from the event has shed light on the rare-but-deadly quakes — and geophysicist Valerie Sahakian thinks she knows how to sense them in time to save lives.

Writing in The Conversation, Sahakian explains the earthquakes’ weird properties. They are slow but produce larger amounts of energy than other quakes of the same magnitude. Because they happen in the soft sediments close to the seafloor in subduction zones — areas where one tectonic plate sinks beneath another — they create more movement than quakes that occur in hard rock. And because they do not shake like a typical quake, people may not realize they need to evacuate.

Scientists have been studying these quakes for a while, but their rarity means they never recorded one up close until the 2010 Mentawai earthquake. After analyzing the data from the quake, Sahakian says she thinks it is possible for researchers to use unexpected data sources to identify tsunami earthquakes. The measurements could one day allow scientists to warn residents to take shelter or evacuate before it is too late.

“We think we have figured out a new way to identify the danger of a future tsunami earthquake, faster,” Sahakian writes. So what is the winning combination? Read her article at bit.ly/tsunamiquake to find out — and for a more in-depth explanation of the unique properties of tsunami quakes.