The quake, measuring at 25km deep, was recorded 45km east of Te Araroa at 8.55am. Image / Geonet
The quake, measuring at 25km deep, was recorded 45km east of Te Araroa at 8.55am. Image / Geonet
A magnitude 5 earthquake has struck off the North Island's East Coast this morning – just as scientists are undertaking a major study in the area.
The quake, measuring at 25km deep, was recorded 45km east of Te Araroa at 8.55am.
While the quake would have caused "moderate shaking" near its epicentre, it was only large enough for 73 people to have reported feeling it on GeoNet's felt app.
About 50 people reported it as "weak", 21 as light, one as moderate and one as extreme. GNS Science seismologist Dr John Ristau said experts quickly discussed the potential of tsunami and found there was no risk.
Ristau said the quake struck in an area where earthquakes were common: its location was just north of a 7.1 event that rattled the East Coast in September2016.
"It's certainly one of the more seismically active places in New Zealand."
The quake came as scientists are installing a 100km-long array of earthquake sensors on the Raukumara Peninsula, which will help build a clearer picture of the country's most dangerous fault line.
During this week scientists from New Zealand, led by GNS Science, and the United States will use seismographs at 700 locations between Gisborne and Opotiki to collect valuable insights into the Hikurangi Subduction Zone, the fault that lies under New Zealand's East Coast.
A large earthquake along the Hikurangi Subduction Zone could cause a devastating tsunami, and a better understanding of the fault will help communities along the East Coast, and other potentially affected parts of New Zealand, become better prepared.
The seismographs will be placed 150m apart from coast to coast, and energy will be generated in boreholes which will send a radiating signal to be recorded by the instruments.
The readings will help scientists build a three-dimensional image of sub-surface rock structures, giving more information about the structure of the plate boundary zone.
Source / GNS Science
"This technique is like producing a CAT scan of the Earth's crust," said project co-ordinator Stuart Henrys from GNS Science.
"We know that in this region, the Pacific tectonic plate is being forced under the Australian plate – but in some places the plates are stuck, and the energy could be released in future earthquakes.
"We have a limited knowledge of how the plates are sliding past each other, so we'll combine results from this project with our previous fieldwork to find out more about where the plates meet.
"The research will also reveal why some parts are locked and other parts are sliding freely."
This is one of several projects involving teams of scientists from around the world researching the Hikurangi Subduction Zone.
Harm van Avendonk from the University of Texas is the lead US scientist on the project, and he says the multiple projects represent a "step change" in understanding how subduction zones work.
"We can use the knowledge gained from this project to help understand other subduction zones around the world and the devastating earthquakes they can generate."
