Infrequent but deadly earthquakes

The 2015 magnitude 6.0 Sabah earthquake took relatively earthquake-free Malaysia by surprise, triggering landslides on Mt Kinabalu that killed 18 hikers on its flanks and injured many more.

“As far as we know, this was the first earthquake of this magnitude to strike Mt Kinabalu in the instrumental records,” says Dr Wang Yu, a Research Fellow at NTU’s Earth Observatory of Singapore, who in the weeks following the rupture conducted a study on the region’s geology together with EOS Founding Director Emeritus Prof Kerry Sieh.

Dr Wang pinpointed the tectonic fault that triggered the earthquake to a location directly beneath Mt Kinabalu, which explained the widespread crumbling of the mountain’s steep surface. “The earthquake ruptured directly underneath the mountain, causing strong shaking and, ultimately, deadly rockfalls,” he says.

By mapping the 200km-long fault system along Sabah’s northwestern coastline, the team found evidence that the fault segments could give rise to earthquakes larger than magnitude 7.0, albeit with a low frequency of once every several thousand years. Based on their new data, they also estimate that earthquakes greater than magnitude 5.0 could occur every 20 years, and those greater than magnitude 6.0 every 150 years.

“Now that we know there is an active fault system in the region that can produce large earthquakes, it is imperative that people and governments take steps to minimise damage and the loss of lives,” Dr Wang concludes.

The study “The 2015 M_W 6.0 Mt Kinabalu earthquake: an infrequent fault rupture within the Crocker fault system of East Malaysia” can be found in Geoscience Letters, DOI: 10.1186/s40562-017- 0072-9.

The article appeared first in NTU’s research & innovation magazine Pushing Frontiers (issue #12, September 2017).