The Trembling Earth

now at blogs.agu.org/tremblingearth

More quake footage from NZ

Yesterday I posted a few videos of the large pair of quakes that struck Christchurch once again on Monday. Since then a few more have surfaced showing the 6.0 as it happened. Clearly even the earthquake-worn residents of Christchurch were startled by such a large temblor.

This man’s home suffered some damage in the 5.5 earlier, so he set up a camera while he went about his business. Sure enough he was startled by a quake “worse than the last one”, recorded here. There’s a very nice separation between the P- and S-wave arrivals here, allowing him plenty of rumbling warning before the real lurching starts. As the shaking winds down you can still hear his stuff being jolted and see the lamp being yanked around as seismic waves continue bouncing around the jello-like sedimentary basin beneath the city.

This kid has similarly coincidental timing, and captured the whole thing unfolding with his family at home. Dad earns some accolades for keeping cool and lookin out for the kids:

A New Zealand Herald reporter was out and about interviewing–presumably about the earlier 5.5–when the 6.0 rocked the neighborhood street where the interview was happening. They witness the liquefaction-mobilized silty water start gurgling out of the ground and flooding the neighborhood; surely an eerie and helpless feeling:

With it becoming clear that their plight may be far from over, the value of the damage from the repetitious onslaught of quakes growing by billions, the logistical nightmare of repairing/disposing of wrecked infrastructure looming, and with the threat of ever less financial protection, Christchurch residents may be understandably approaching their wits’ ends.

Unfortunately this is a case where the incompatible timescales of tectonics and humanity collide. These quakes do not signal any sort of new tectonic regime nor indicate that the seismic behavior of the region has changed. They merely represent an unfortunately prolonged little geological burp–a transient period during which a little bit of strain that must be accommodated is occurring in insufficient fits every couple of months. Eventually Christchurch will quiet down, with earthquake recurrence once again far below that of plate-boundary-adjacent regions like Japan, California, Alaska, Chile, the Himalaya, Indonesia, and the west side of their own South Island, to name a few. Until then the population faces a very real hardship: more destructive earthquakes may dot the near future, and the soupy emissions from liquefaction are gradually unsettling foundations across the region. These are problems residents will have to make serious decisions about. Unfortunately human time scales can’t wait on geology to quiet down.

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