So, ‘authorities reveal all’ about new fault knowledge and aftershock forecasts, but is it enough? Or even correct? Geologists and politicians are yet to prove themselves reliable in Christchurch, New Zealand.

New faults fail to dull optimism “..a 25-kilometre-long fault under the sea off Kaiapoi. Two faults run almost directly below central Christchurch and two patches containing possible small faults – one off the Brighton coast and the second just north of Port Levy and Pigeon Bay.. The tsunami risk from the large offshore fault is believed to be very low because it is unlikely to generate a quake higher than magnitude 7.0. Also, its past movement has been mostly horizontal rather than vertical. There is no sign that aftershocks are spreading offshore onto, or close to, it or other already recognised Pegasus Bay faults. The offshore faults are very slow moving, among the slowest moving in the country” / When gossip fills the gap Press 4Jun11

NIWA/GNS Christchurch/Kaiapoi submarine faults 030611

NIWA/GNS Christchurch/Kaiapoi submarine faults 030611


Graphic source: @NIWA

Another view? Let us scan the deep offshore topography using Google-maps:

Chatham Rise Google-map view

Chatham Rise Google-map view

Closer-up note the long ravines most likely formed by substantial faults:

Pegasus Bay - Googlemap

Pegasus Bay - Googlemap

Add in some GNS data on Google maps, with the Greendale and Lyttelton faults, the previously mapped and newly-discovered faults, and some indicative deep unlisted faults drawn on in yellow:

GNS quakes 220211-060311 on Pegasus Bay Google-map + possible new faults

GNS quakes 220211-060311 on Pegasus Bay Google-map + possible new faults

With the onshore and offshore fault-mapping output released this past week having such limited range regarding ocean depth, is the potential for large local quakes not consequently much greater than we know so far?

The Chatham Rise Google-map reveals long striations that also could use explanation vis-a-vis the large earthquake risk posed by them, though less so as potential tsunami sources – that much (horizontal fault movement does not displace much water) of the scientific explanation does make sense.

Building upon the analytic predictive work I commenced from the 4 September 2010 earthquake magnitude 7.1, that created appropriate warning for the consequent and deadly 6.3, I have now started a new set of notes for the 22 February 2011 earthquake and will build research and insights there for summary on this blog.

~ Kia ora

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