Scientists warn that quake-rattled Christchurch faces a 72 per cent probability of being hit by an earthquake measuring between 5 and 5.4 magnitude in the next year.
GNS Science figures show the city has had 58 earthquakes over magnitude 5 since September 4, 2010. They also say there is 31 per cent probability of a 5.5 to 5.9 earthquake in the wider Christchurch area over the next 12 months, but only a 3 per cent chance of an earthquake over 6.5.
The principal scientist at GNS Science in Wellington, Martin Reyners, will give a public lecture on earthquakes at the University of Canterbury next week. He will explain why Canterbury has faced a long series of aftershocks, why the fault ruptures produce a lot of energy, and why it is happening.
Dr Reyners said he will ask in his lecture what if events 100 million years ago controlled the Canterbury earthquake sequence. The Canterbury earthquakes had raised important questions regarding the seismic hazard of the region.
“Such as why has there been a concentration of large aftershocks in the Christchurch area, at the eastern end of the magnitude 7.1 Darfield earthquake rupture? Why has the pattern of faulting been so complex?
Why has the aftershock sequence been so prolonged? And why has the shaking from the Darfield earthquake and its larger aftershocks been so strong, compared to most earthquakes of similar magnitude worldwide?”
Dr Reyners will address these questions in terms of the unusual structure of the Earth’s crust beneath Canterbury, and its response to the current convergence of the Pacific and Australian tectonic plates. He has used data from well-recorded Canterbury aftershocks to build a three-dimensional model of the crustal structure of the region.