The powerful earthquake that struck New Zealand early on Sunday might have been the result of not one but two seismic calamities. There is now speculation that a slippage on one geological fault line might have immediately triggered a collapse on a second, scientists said yesterday.The earthquake, of a hefty magnitude 7.8, pummelled central New Zealand, killing at least two people and damaging roads and buildings. It was followed by hundreds of strong aftershocks."When an earthquake occurs you are changing the stress field immediately and if there was another fault that was pretty close to breaking the energy from the earthquake could tip it over the edge," said Adam Pascale, head of Australia's Seismology Research Centre.The principal scientist of New Zealand's GNS Science agency, Kelvin Barrowman, told Radio New Zealand: "It seems like the earthquake was more like two [almost simultaneous] earthquakes."What remains unknown and disconcerting is whether the aftershocks were just that - or "foreshocks" preceding another big quake.A 9.0-magnitude earthquake in Japan in 2011, which triggered a tsunami and killed thousands of people, was preceded by a quake of magnitude 7.3 and three magnitude-6.0 quakes.The effects were felt around the world. More than 5000 aftershocks hit Japan the following year, the largest of magnitude 7.9. ..