COOK STRAIT EARTHQUAKES ~ maps ~2010

20 November 2010

November 15-20

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Preliminary data 11 Events 2.244ML to 4.172ML
(updated 20.11.2010 NZDT)

data by geonet. maps by google maps. plots by highace using GPS Visualizer

November 8-15

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Preliminary data 12 Events 2.225ML to 3.099ML
(updated 20.11.2010 NZST)

data by geonet. maps by google maps. plots by highace using GPS Visualizer

November 1-7

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Preliminary data 57 Events 1.352ML to 4.289ML
(updated 20.11.2010 NZDT)

data by geonet. maps by google maps. plots by highace using GPS Visualizer

04 November 2010

October 22-31

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Preliminary data 29 Events 2.192ML to 3.318ML
(updated 04.11.2010 NZDT)

data by geonet. maps by google maps. plots by highace using GPS Visualizer

October 15-21

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Preliminary data 14 Events 1.744ML to 3.151ML
(updated 04.11.2010 NZDT)

data by geonet. maps by google maps. plots by highace using GPS Visualizer

October 8-14

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Preliminary data 34 Events 1.7ML to 3.987ML
(updated 04.11.2010 NZST)

data by geonet. maps by google maps. plots by highace using GPS Visualizer

11 October 2010

October 1-7

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Preliminary data 18 Events 2.083ML to 3.67ML
(updated 11.10.2010 NZST)

data by geonet. maps by google maps. plots by highace using GPS Visualizer

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HOW IT WORKS

click on markers for pop up tag showing details of the earthquake event.
Zoom in, zoom out, change from Terrain to Maps, to Satellite or Google Earth as you please, the marker will remain in position.
By clicking and holding down your left button on your mouse on the map you can move the map around inside the frame to see larger popup tags, click once to make the tag go away.

At the bottom of each map there are the words View Larger Map in blue. Clicking on this will open a larger map (in the same window/tag) with a list of the events on the map to the left. Clicking on an item in the list will make a pop up tag appear at the location on the map.
Return to 40to42south by clicking your Back arrow.

BACKGROUND

When Dutch explorer Abel Janszoon Tasman first saw New Zealand in1642, he interpreted the Cook Strait area as a bight closed to the east. He named it Zeehaen's Bight, after one of the two ships in his expedition.
Below is a reproduction of the map Abel Tasman made back in 1642;

When Captain James Cook of the Royal Navy was exploring the South Pacific this bight was shown on Visscher's chart as Zeehaen's Bight but the Dutch had not determined if it was only a bay or the entrance to a passage back to the Pacific. Cook sailed on to find out the answer and on January 14th 1770 as he passed Kapiti, or Entry Island, he could see no end to the bay.

12th January 1770. Captain James Cook's account:
"At five the next morning, we steered S.E. by S. the coast inclining more southerly; and in about half an hour, we saw land bearing S.W. by S. for which we hauled up. At noon the north west extremity of the land in sight bore S. 63 W. and some high land, which had the appearance of an island lying under the main, bore S.S.E. distant five leagues. We were now in a bay, the bottom of which bearing south we could not see, though it was clear in that quarter. Our latitude by observation was 40.27 S. longitude 184.39W. At eight in the evening, we were within two leagues of the land which we had discovered in the morning, having run ten leagues since noon: the land which then bore S. 63 W. now bore N. 59 W. at the distance of seven or eight leagues, and had the appearance of an island.
Between this land and Cape Egmont (Mt. Taranaki) lies the bay, the west side of which was our situation at this time, and the land here is of a considerable height, and diversified by hill and valley"

On January 22, 1770, Cook rowed up Queen Charlotte Sound with Banks and Solander in the pinnace for about fifteen miles; but not finding an exit and accompanied by one sailor, he climbed a hill (1,268
feet) on the southeast side (on the present Arapawa Island). To the south, the intervening hills still seemed to hide the exit he sought (into Tory Channel). But he had abundant recompense for his trouble. Of a sudden he saw to the east what surely must be one of the fairest panoramas on earth. In the foreground were various inlets, their connections with the sound and the outlet of the channel still hidden. And just beyond the wooded hills lay a breath-taking sight of blue water extending unmistakably across his line of sight.

"I saw what I took to be the Eastern Sea and a strait or passage from it into the Western Sea. The land on the opposite side seem'd to trend away East as far as the Eye could see, to the SE appear'd as oppen Sea and this I took to be the Eastern.

He was looking northeast and east across Cook Strait that connects the Pacific Ocean with the Tasman Sea, and on the far side he could trace the coast of North Island extending southwest until it curves into the present location of Wellington Harbor. With no more effort than that of climbing a steep hill, Cook had solved the geographic problem that had eluded Tasman.

Cook Strait attracted European settlers in the early 19th century. Because of its use as a whale migration route, whalers established bases in the Marlborough Sounds and in the Kapiti area. From 1840 more permanent settlements sprang up, first at Wellington, then at Nelson and at Wanganui (Petre).

Captain Furneaux feels earthquake
On 10th May 1773, at Ship Cove, in the Marlborough Sounds Captain Furneaux of the 'Adventure' wintering at Motuara, records that "his shore-party felt two severe shocks of an earthquake , but received no kind of damage."

This was the first official written recording of an earthquake in New Zealand.

Cook Strait Faults
Four major faultlines run through the land mass north of Cook Strait (Lower North Island). The West Wairarapa fault runs through the Rimutaka Range; the Ohariu Fault runs close to the west coast, intersecting Porirua Harbour; while the Pukerua Fault starts at Oteranga Bay then continues along the coast. The Wellington Fault begins at Sinclair Head and carries right through the city along the western side of the harbour and through the Hutt Valley to the Tararua Range. Secondary splinter faultlines run off these primary faults, forming valleys.
The map below shows the " known" fault lines in the area.

Quake Frequency
On average there is normally a 2.0-2.9 and/or a 3.0-3.9ML quake somewhere in Cook Strait 5 out of 7 days a week, sometimes up to 4 per day.
Larger quakes are not so common.
Starting from the date 1942, and without going into too much detail here, on average most years there were at least one to three 5.0-5.9ML sized quakes (offshore) per year, except for the years 1944, 1947, 1958, 1960, 1962, 1963, 1964, 1978, 1990, 2001 and 2004 when there were no quakes above 5.0ML.

Noteable years for 5+ quakes (since 1942) were... 1948-(one 6.3ML and 3x 5.0+ML), 1949-(one 6.4Ml
and 2x 5.0+ML), 1950-(7x 5.0+ML), 1954-(4x 5.0+ML), 1959-(4x 5.0+ML), 1974-(5x 5.0+ML) and 2000-(5x 5.0+ML).
6.0- 6.4ML quakes occured in the following years, 1948-6.3, 1949-6.4, 1974-6.0, 1989-6.1, 1991-6.3, 1995-6.6 and 6.4, 2005-6.4, 2006-6.0.

All the large quakes above 6.5ML occured prior to 1897.

The map below is the area I have interpreted as Cook Strait, - from Wanganui in the N down the coast and through to Cape Palliser, Wellington in the SE, across to Cape Campbell in the South Island then along the coast through the Marlborough Sounds to the west of D' Urville Island then N to Wanganui.
I have plotted the 5.0ML plus earthquakes since 1840.
The largest earthquake ever recorded in New Zealand the Wairarapa 8.2 of 1855 has over the years been shown on maps in various locations, the latitude and longitude I have used is the latest researched estimated location on the western shore of Lake Wairarapa.

My favourite photos of Cook Strait, taken from the International Space Station