Christchurch City (population 320,000) sits at the base of the long arc of Pegasus Bay, (click title to entry - thank you) bounded to the north by the Waimakariri River and to the south by the old crater complex of the Port Hills and Banks Peninsula.The heavily braided rivers of the South Island of New Zealand bring greywacke rock from the Southern Alps to the west, forming the huge alluvial pan (750,000 ha) of the Canterbury Plains. Braided rivers are rare worldwide, found elsewhere only in Alaska, Canada, and the Himalayas. They form a network of ever-changing channels weaving between temporary shingle islands. In some places, the gravel they have transported from the mountains formed by the clash of the Indo-Australian and Pacific Plates is as much as 500 meters deep.
Banks Peninsula, named for explorer Captain Cook’s botanist, consists of two overlapping extinct volcanoes, the Lyttelton Volcano and the Akaroa Volcano. Since the last eruptive activity some six million years ago, the volcanoes have been heavily eroded, dropping them from a peak of 1,500 meters down to around 500 meters....
...At least three aftershocks have hit Christchurch in quick succession this evening. (click here)
According to GeoNet, the latest, at 8.01pm, was a magnitude 4 quake centred within 5km of Christchurch at a depth of 9km.
Three minutes earlier another shock hit, a 4.1 magnitude quake centred within 5km of Christchurch at a depth of 7km.
Twelve minutes before that, there was a 3.8 magnitude shock centred within 5km of Christchurch at a depth of 8km.
These followed a 4.46pm magnitude 4 quake centred 10km southwest of Darfield at a depth of 5km, and a 4.3 shock at 9.22am that was centred 20km southwest of Christchurch at a depth of 15km.
Today's shocks were felt widely in the area but it is not believed they caused any further damage....
...Breaches in the crater walls have produced two long harbors: Lyttelton to the north and Akaroa to the south....
No different than the major instability in China and casualties there experienced quakes for some time, I would expect the same here. The mountains do not provide stability to the eastern coast, they provide instability by their 'mass and weight' alone.
The people of New Zealand's south island have faired well to date. I am sure they are impatient for 'quiet.' The geologists need to explore the role the mountains are playing to determine how long and to what extent the peninsula will continue to receive these quakes.
...At least three aftershocks have hit Christchurch in quick succession this evening. (click here)
According to GeoNet, the latest, at 8.01pm, was a magnitude 4 quake centred within 5km of Christchurch at a depth of 9km.
Three minutes earlier another shock hit, a 4.1 magnitude quake centred within 5km of Christchurch at a depth of 7km.
Twelve minutes before that, there was a 3.8 magnitude shock centred within 5km of Christchurch at a depth of 8km.
These followed a 4.46pm magnitude 4 quake centred 10km southwest of Darfield at a depth of 5km, and a 4.3 shock at 9.22am that was centred 20km southwest of Christchurch at a depth of 15km.
Today's shocks were felt widely in the area but it is not believed they caused any further damage....
From the NASA assessment:
...Breaches in the crater walls have produced two long harbors: Lyttelton to the north and Akaroa to the south....
The land masses on the western side of the south island are significantly larger and denser than that of the east side of the south island.
No different than the major instability in China and casualties there experienced quakes for some time, I would expect the same here. The mountains do not provide stability to the eastern coast, they provide instability by their 'mass and weight' alone.
