A map of the 7.5 magnitude earthquake in PNG released by the United States Geological Survey (USGS) showing populated areas exposed to shaking. Image provided by USGS.
Around 30 people are thought to have been killed and around 300 injured after a powerful earthquake struck the southern highlands of Papua New Guinea on February 26.
The quake hit early on the morning of February 26, at a relatively shallow depth of 35 kilometres, the epicentre 96 kilometres from the provincial capital Mendi, home to 50,00 people.
Associate Professor Steven Micklethwaite from the School of Earth, Atmosphere and Environment at Monash University said that this earthquake is a significant geological event.
“Papua New Guinea is one of the most tectonically complex regions on Earth and is shaken by earthquakes routinely, including big ones such as this. There are some characteristics of this particular event that make it stand out, though,” he said.
“The initial data released by the USGS suggest it was what scientists call a thrust earthquake, occurring at 35 kilometres deep at the margin of the Southern Highlands. The estimate of the 35 kilometre depth will not necessarily be very good, but we can always expect extensive damage when an earthquake greater than magnitude six occurs somewhere in the top 30 km of the crust. A magnitude 7.5 event as this was should have ruptured massive areas of the crust (at least 80 km long) and propagated all the way to the surface,” he said.
“Thankfully, the event does not appear to have hit a large city or town. The biggest concern will be secondary events, such as landslides, flash floods from blocked rivers, and aftershocks striking nearby towns.”
Associate Professor Behzad Fatahi is from the Centre for Built Infrastructure Research at the University of Technology Sydney (UTS) said that this event was caused by the northward movement of the Australian continent.
“This earthquake has happened as a result of younger rock formations being pushed above older rocks as a result of Australian Tectonic Plate (south west) pressing against Pacific Tectonic plate (north east), creating compressive stresses. It is estimated that these tectonic plates move around 100mm per year toward each other, and the fault rupture in the order of 75 km occurred in this earthquake,” he said.
“Vast areas of central Papua New Guinea, particularly in Highlands Regions comprise of crystalline rock formations overlain by sedimentary rocks. There are several major mining sites in the region, such as Porgera Gold Mine, that need to be inspected for possible cracks and open pit instability. In addition, the Liquid Nitrogen Gas (LNG) area near Port Moresby needs to be checked for probable ground subsidence and impacts on pipelines and LNG tanks since there is a chance of sliding and deformation of foundations after this earthquake.”
Aftershocks are expected to continue in the following days and weeks in the Southern Highlands province, from southwest of Mendi to within 125 kilometres of Tabubil, near the PNG border with West Irian.
A 7.0 magnitude earthquake in north Papua killed over 2,000 people and injured thousands more.
