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Probabilty of more Christchurch quakes?

by apeiron
Tags: christchurch, probabilty, quakes
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Mar1-11, 05:20 PM
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Yes I live in Christchurch under the bit that hasn't been broken. But check the map and you can see that our story could be one of a large lateral fault in the middle of its creation.

At first I could believe this was unlikely (having good access to local scientists who know the geology). The story was the original quake was an existing mag 7 faultine buried under some 20k years of alluvial gravel. But recently it has become suggested it was instead four lesser cracks becoming lined up.

And now we have had a 6.3 very shallow fault that looks like an extension of the previous line of stress. And in turn, that there is a further big chunk of potential fault inbetween now waiting to go. A line that in fact runs through my house along with the rest of the unbroken part of town.

So any experts out there want to look at the maps and hazard some opinions?

It is already accepted here that smaller lateral faults to the Alpine fault are assembling into larger ones all down the east coast of New Zealand. There are a bunch of about seven (including the Hope, Awatere, etc) running from Wellington down to Kaikoura, and one known to be assembling at the southern end. Christchurch would now be the same happening even further south. And perhaps wanting to complete the job in six months, six years, who knows?

Check this geonet map to see early view of where the Christchurch faults lie.

Here is the story on the laterals further north.

And then this comment from our top earthquake guru, Kelvin Berryman, just yesterday about the new questions.

Berryman said the faults associated with the September 4 and February 22 quakes were separated by what may be at least two more hidden faults underneath Christchurch.

Aftershock patterns suggested at least two north-east-south-west trending faults lay between the east-west Greendale Fault exposed at the surface in September last year and the fault under the Port Hills.

Scientists originally thought there had been 17km of subsurface rupture between Halswell and Taylors Mistake. However, that had been refined to movement over an 8km-wide and 8km-long area.

"It's not a big fault. It hasn't had a lot of movement on it in the past. "The quake occurred at the periphery of the September 4 aftershock cloud. "The stress front has arrived there and found a piece of the crust that was primed and ready to go."There was no indication how long it was since the Port Hills fault last moved, Berryman said.

"It has not been determined before now in any geological maps or geophysics work. "It could have moved before, but it might be the first time it ruptured in the last 100 million years," Berryman said.
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