Joining the dots

Thanks to a very cool GNS chart that a commenter recommended:

Last 10 years of earthquakes in NZ

nz_earthquake_map_30-12-1997to30-12-2007

(Stewart Island is in the lower left corner)

Legend

(magnitudes not to scale)

According to the theory that the tectonic plate to the East is sliding underneath the Western plate we should see some seismological evidence - and we do. Some commenters in the post below have sided with Beaker's random theory of earthquake activity:
Six *reported* quakes over a 10 day period is perfectly to be expected and doesn't signify anything (there were actually 49 3.5+ quakes in that period). Random events *do* form apparent clusters [...] The reason you *heard* about lots of quakes is that the news media will report small quakes after a newsworthy large one - especially at Christmas with a lack of other (domestic) news. Media aftershocks, not seismic ones.

Well really? The cluster (as shown below in the last ten days image) does signify something, "apparent clusters" are the bread and butter of scientific observations, and after the main quake (that affected Gisborne) this "apparent cluster" can be observed independently of the media to have been accompanied by other quakes occuring in a very localised area within days of each other. So let's put it in perspective:

Seismic activity over the last year:

/nz_earthquake_map_30-12-2006to30-12-2007


And the preceeding 50 days:

nz_earthquake_map_19-10-2007to19-12-2007


And the last ten days. The cluster near Gisborne is clear as are the two bigger deep quakes in the middle of the island (if they are unrelated it is still obvious that the ones around Gisborne are a strong pattern):

nz_earthquake_map_20-12-2007to30-12-2007


And what was the activity like on those 10 days over the last ten years? (to determine whether these recent events are not unusual - as some commenters have implied)

nz_earthquake_map_20-30Dec2006

nz_earthquake_map_20-30Dec2005

/nz_earthquake_map_20-30Dec2004

/nz_earthquake_map_20-30Dec2003

nz_earthquake_map_20-30Dec2002

nz_earthquake_map_20-30Dec2001

nz_earthquake_map_20-30Dec2000

nz_earthquake_map_20-30Dec1999

nz_earthquake_map_20-30Dec1998

nz_earthquake_map_20-30Dec1997