Friday, February 24, 2012
The patterns of earthquakes
The new hope gently taking shape in Christchurch is that the aftershocks continuously rumbling the city are getting less violent and heading inexorably north and east. Away from the city and out to sea.
The Ministry for Culture and Heritage has put together a pretty interesting infographic about the Christchurch earthquake in particular and the history of earthquakes in New Zealand in general. This shows how the more than 10,000 aftershocks since the first, 7.1 quake in September 2010, are patterned. I'm no scientist, but this does indeed seem to show that there has been a trend of movement.
The 7.1 September quake was west of the city, near Darfield. The February 22 quake - dubbed the Lyttelton quake - was virtually right under the city and, at a depth of just 5 kilometers, very shallow. This quake was so strong it generated its own series of aftershocks. Since then the big ones have been moving east, and all the recent earthquakes above 5.0 have been in Pegasus Bay.
Of course none of this really means anything, as seismologists freely admit. Progress for them is learning more about how little they know and how limited their predictive skills really are. Until then, placing flowers in cones may be the best way for Cantabrians making the best of a bad - but improving - situation.