Weekend swarm in Porangahau

Published: Sun Jan 28 2018 12:30 PM

This weekend has been an active one for earthquakes around the coastal Hawkes Bay town of Porangahau.

Starting with an M3 earthquake last Friday night, there have been over 30 small earthquakes detected by the GeoNet network. Most of these are too weak to have been felt by many (if any!) New Zealanders, as they are quite small and many of the epicentres are off the coast.

Location of the Porangahau earthquake swarm

Location of the Porangahau earthquake swarm

This isn’t the first time this area has experienced heightened seismic activity. In fact, over the past decade, this area has been relatively seismically active. We have learned that this is an area that is very sensitive to changing conditions that happen whenever the ground shakes or moves. Whenever it experiences the effects of a strong regional earthquake (e.g. the M7.8 Kaikoura earthquake) or local Slow Slip Events, it commonly responds by generating swarms of relatively small earthquakes (you can read more about the history of SSE and earthquakes in the area, here)

Exactly why this region appears to behave a bit differently than others around it is still a mystery, but one that is keeping GNS Science seismologists busy looking for an answer. Perhaps solving this question will leave us better able to forecast large subduction earthquakes that might impact New Zealand in the future.

What does this all mean for those of you living in the region around these earthquakes? It certainly does not mean that a large and damaging earthquake is imminent. However, it is a reminder that dangerous earthquakes can happen at any time in New Zealand and all New Zealanders, including those from Porangahau, should be prepared for future damaging earthquakes.

Science information: Bill Fry, Duty Seismologist.

We can’t stop large earthquakes from happening BUT we can prepare for them. Want to know how? Here are some great places to go to get more information about New Zealand and preparing for earthquakes and tsunamis:

If you are near the coast and feel an earthquake that is LONG or STRONG: GET GONE.

Long or Strong Get Gone

Long or Strong Get Gone