Earthquakes Near Matawai

The town of Matawai, inland from Gisborne, has been close to a series of light to moderate, deep earthquakes this year.

Since the late 19th century, the town of Matawai has been an important staging point for travelers taking the tortuous inland route between the Bay of Plenty and Gisborne districts.

It’s a rugged mountain town that sits between the lush Poverty Bay Flats and the mountain pass that allows travellers to move between the two districts. Matawai services the local farming community and provides a farewell point for westward travellers bound for the picturesque Waioeka Gorge as well as providing a welcome for travellers on State Highway 2 looking forward to seeing the Pacific Ocean beaches on the North Island’s eastern coast.

Travellers on the highway from Gisborne are often unaware of the steady climb up to Matawai, where they swing a sharp left at the Matawai Hotel and head inland on the road out of the town on their way to the Bay of Plenty. However, as they virtually plunge off the edge of the plateau into a steep gully, they are treated to their first glimpse of dramatic scenery uplifted by thousands of years of seismic activity.

Ahead of them lies Trafford’s Hill with a steady climb to its 725m above sea level summit, before a steep zig-zag takes them down to the beginning of the picturesque Waioeka Gorge. The gorge road winds for about 45 km through rugged, cool and dramatic scenery past Midway Camp where many men lived while they built and maintained the road last century. Steep rock faces, rain-fed waterfalls and mountain streams crowd the road, and there are many picnic spots beside the gravelly river.

This area sits on a “shoulder” of New Zealand’s North Island where the Australian tectonic plate is being crushed and folded over millions of years as the Pacific tectonic plate slides underneath it.

Since the beginning of the year, there have been four light to moderate earthquakes within 30 km of Matawai, at a depth where the two tectonic plates are slowly grinding past each other. It is thought that the plates move relatively smoothly in the area, but the combined pressure causes deformation in the overlying plate forming the Huiarau and Raukumara mountain ranges.

In recent years it has been noted that some of the earthquakes on plate interfaces are caused by lumps and layers on the sub-ducting (underlying) plate being scraped off by the overlying material as the tectonic plate slowly inches forward to be recycled into magma at greater depths.

This mechanism may explain the earthquakes that have occurred in the area since the beginning of the year. The quakes reported by Geonet this year are:

January 8th, 2:31 a.m., magnitude 4.3, 50 km deep, 20 km north of Matawai
May 24th, 6:33 p.m., magnitude 4.3, 40 km deep, 30 km west of Matawai
October 21st, 10:21 p.m., magnitude 4.5, 60 km deep, within 5 km of Matawai
December 5th, 7:59 a.m., magnitude 5.1, 40 km deep, 10 km north of Matawai

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