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Colin Skinner
My Visits to
Inangahua Junction
and Earthquake Flat

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Inangahua Junction
During recorded history, six major earthquakes have occurred in the mountainous area at the top of the South Island. In the last quake, around Inangahua Junction in 1968, there were landslides and damage to roads, buildings, and bridges. Three people died. I walked through the valley there and found what used to be the old road. It lay buried beneath dead trees, boulders, and earth. I clambered over rocks and vegetation and saw a patch of asphalt tilted at an angle of 45 degrees. Beneath white cliffs, which had not existed before 1968, there were now just rocks and earth where a house used to stand. A track that once led to the old house just ended in a pile of earth beneath the cliffs. It was peaceful in the valley, but as I gazed at the cliffs by the new road, I wondered if the next big quake was just around the corner.

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Earthquake Flat
I didn't feel a quake that day, but I did earlier in my walk. At Rotorua, there were 100 tremors in one day. The most impressive tremor shook the walls of the cabin I was staying in for several seconds. That night I woke at about 2:30 a.m., as my bed shook from side to side. What causes the earth here to shake so much? Remember that New Zealand is located above a point where two plates of the earth's crust collide. The colliding plates put pressure on the rock above. Every so often the pressure becomes too much and the rock breaks along lines called faults. First, rock layers are squeezed by the sudden movement. Then the earth shakes from side to side and up and down. All this shaking releases the energy from the initial shock of the movement of the ground.

Walking south from Rotorua, I passed through Earthquake Flat, where a thousand earthquakes a year are monitored by seismologists, scientists who study earthquakes. At Taupo, I talked to seismologist Dr. Steve Sherburn, who works at the Institute of Geological and Nuclear Sciences (IGNS). He showed me how the seismographs that measure earthquakes work: "Sensors are located at points where the earth shakes. These sensors have a large weight inside, wrapped with a coil of wire. The weights are hung on springs and sit inside a magnet. When the earth shakes, the weight moves up and down on the spring. The coil moving in the magnetic field generates an electric current in the wire. The size of the current gives us a measurement of the movement that caused it. This is recorded by a pen that moves across a roll of paper. Information from the seismographs can provide warnings about earthquakes and volcanic eruptions." When Mount Ruapehu erupted in 1996 a large tremor was detected 36 hours before the eruption, allowing the IGNS to warn skiers to stay off the snow covered volcano.

One of the places most at risk from earthquakes is Wellington, the capital of New Zealand. A motorway in the city was built on land that emerged from the sea after an earthquake in 1855. Presumably this land could disappear just as quickly as it formed. The Parliament House and the Parliament Library are only 400 meters away from a major fault line. These buildings, now about 100 years old, are built of brick, marble, and glass. To protect the buildings from earthquake damage, they have been separated from their foundations by 417 bearings of rubber, steel, and lead. The buildings can now sway 30 cm, and are safe in earthquakes up to 7.5 on the Richter Scale. .

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During an earthquake that measured 7.1 on the Richter scale, a landslide covered this old road at Inangahua Junction with earth, boulders, and dead trees.

A house lies buried beneath the cliffs at Inangahua Junction, evidence of earthquake destruction.

Seismologist Dr. Steve Sherburn with the seismograph for White Island

New Zealand's Parliment House and Library sit on rubber bearings, protecting the buildings from earthquake damage.

Earthquake Gully Road sign near Taupo. How would you fancy that address?

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