Hidden Earthquakes: the March 2013 Auckland Earthquake Swarm

Following up on one of my last posts about the Auckland earthquakes in March…

What you may not have realised is that we didn’t just have the one or two felt earthquakes in March, we had many! Unless you were checking out GeoNet, you would never have known that there were more earthquakes out near Motutapu–they were too small and deep for people to feel. 

2013-03-19 Motutapu Island Quakes

Many of the earthquakes in the March 2013 earthquakes near Auckland. Only two of them were large and/or shallow enough for people to feel on the mainland. Image courtesy of Richard Woods (Auckland Council Civil Defence and Emergency Management Planning & Intelligence Manager) and GeoNet.

This kind of cluster of earthquakes is called an earthquake swarm. They happen all over the world, not just near volcanoes. Auckland also experienced earthquake swarms in 2005 and 2007–so though the 2013 swarm caused quite a stir, it was actually business-as-usual. Earthquakes are just a part of New Zealand life, and will be for a very long time. It is best to expect and prepare for them.

As I mentioned in one of my last posts, seismologists deemed these earthquakes tectonic–not related to rising magma or the volcanic field at all. Nevertheless, this swarm provided a good opportunity for us to learn a little bit more about the Auckland Volcanic Field (and for me to ditch the office for a few days and get out in the field, which I love!). More on what we were doing in future posts!

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