Could Monday’s quake trigger a sleeper tsunami or an Alpine Fault quake? Are we living in an era of quakes? Science reporter Jamie Morton tackles five big questions facing scientists.
1. Has the quake increased the chance of a sleeper tsunami?
One potentially increased threat is a rapid-fire tsunami from the submarine Kaikoura Canyon – which recent modelling has shown is capable of generating a wave with a crest 13m above sea level.
The huge canyon comes up to within 500m of the coast south of Kaikoura and feeds sediment into the 1500km-long Hikurangi Channel that runs east of New Zealand.
It posed a unique threat due its combination of factors, including very shallow water next to the canyon edge; steep slopes of the canyon which drops off down to 1000m; large areas where there might be weak sediment; large earthquake sources nearby; and all of it very close to the highway and populated areas.
In 2006, scientists from the National Institute of Water and Atmosphere (Niwa) said that a possibly severe tsunami off the Kaikoura coast could be triggered by either a submarine earthquake, or underwater landslides that occurred at the canyon’s head every 200 years on average.
Niwa marine geologist Dr Joshu Mountjoy, who has assessed the threat over recent years, told the Herald this morning it was unclear what Monday’s 7.5 earthquake could have meant for the canyon’s stability.
“One of the faults most likely ruptured right through the head of the canyon, so there’ll be plenty to see there.”
Mountjoy said there was yet no indication of a landslide-generated tsunami, and if one had occurred, the coast being uplifted by a metre would have mitigated the tsunami’s run-up on land.