8/6/2023 0 Comments Miki endo recordingWhen the Kaikoura Earthquake erupted in November 2016, with the equivalent energy release of 400 atomic bombs, shockwaves travelled hundreds of kilometres through the ground and triggered a series of faults as they spread. "Everything we learn about them makes us realise how little we actually know." "The discovery of slow slip events in the last 20 years has caused us to completely re-think how faults work," said Dr Laura Wallace, a geodesist at GNS Science. Other studies have tied these slow slip episodes to two big quakes in 2014: slow slip events were thought to precede the 8.1 Iquique earthquake in Chile, and a 7.2 shake off the coast of Mexico that hit just two months after a slow slip started. When one of these slow-slip quakes are under way, scientists are now paying close attention, as they may provide clues into the occurrence of future earthquakes. Their research pointed to a deep-seated, almost imperceptible motion known as "slow slip" – a phenomenon common in our own subduction zone, where they'd actually been first observed using GPS in 2002.Īlso known as silent earthquakes, slow-slip events can last from days to years, and can produce up to tens of centimetres of displacements along faults without seismologists even realising it. "When we talk about recurrence intervals, people shouldn't assume we are talking about something that's fairly regular – and we know enough about action on the Hikurangi Margin that it does not appear be regular." A SILENT THREATĪfter Tohoku, scientists trawled through data from thousands of earthquakes in the region to pin-point one peculiar culprit behind the sudden megathrust. When it came to the whole margin going at once – think a 9.0 quake the size of Tohoku – the recurrence was probably far less frequent, although the evidence for such monster events remained sparse.Īnd Clark also emphasised that cataclysmic quakes didn't keep a tidy schedule. Gisborne was also vulnerable to a quick-fire tsunami, with the city's beach front, and north of Muriwai at the end of Poverty Bay, most at risk.Ĭhristchurch would be hit particularly hard, said University of California Santa Cruz geophysicist Steven Ward, who created the new simulation.Ĭlark and colleagues have also calculated the recurrence intervals of large events, which suggested one happening every 550 to 1400 years. In Napier, a tsunami up to 8m high could plough through the low-lying city within minutes of an earthquake, reaching as far as 5km inland – and more waves could come over following hours. It would bring "extremely damaging and deadly inundation" in low-lying southern suburbs of Wellington, along with damaging and moderately deadly inundation in busy areas bordering Lambton harbour. One GNS Science report found this catastrophic event could cause 40 deaths due to earthquake shaking - but a further 3200 in a tsunami that followed.Īlthough scientists were uncertain whether a rupture could extend from the subduction zone to the Cook Strait, such an eventuality could send tsunami waves 5m to 10m high barrelling toward the capital. It was odd reality to consider, given the fact only one person has ever been killed in the 10 tsunamis higher than 5m that New Zealand has experienced since 1840.īut it was because of such luck that the size and nature of our tsunami risk had not been widely understood, nor had the required responses been "widely appreciated", the authors noted.Ī new simulation released this week suggested tsunami waves - up to 12m high in places - could inundate the coastline within an hour if a "megathrust" earthquake struck here. That death toll was also one or two orders of magnitude larger than our largest national disasters: the Erebus air crash, the Napier earthquake and Tangiwai. Headline projections in an EQC-commissioned report estimated worst-case scenario impacts from a one-in-500 year event could include 33,000 fatalities, 27,000 injuries and $45b worth of property loss. The two world wars were the bloodiest events in New Zealand's history, yet recent research has found a cataclysmic tsunami had the potential to be costlier for us than both put together.
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