Early investigations have suggested that the shallow earthquake was an aftershock of the September quake in Darfield, but did not come from the same faultline. Tests indicated it occurred on a "blind" or unknown fault, which runs east to west 1km north of Lyttelton. This meant that - like the Darfield fault that had lain dormant for at least 16,000 years - the Lyttelton faultline had been accumulating extreme pressure over centuries, before collapsing catastrophically. Experts said the enormous aftershock was statistically UNUSUAL. Generally aftershocks get smaller and less frequent as months go by. "With the decay of the Darfield event, many of us would have breathed a sigh of relief - until Tuesday." The quake was a "strike-slip event with oblique motion", meaning the earth moved mostly side-to-side but occasionally up-and-down. The vertical acceleration of the earth, at 1.9 times the acceleration of gravity, was far greater than the sideways movement. "Anything you put at nearly 2g - it's like lifting a building and dropping it to the ground." The simultaneous vertical and horizontal seismic shifts made it almost impossible for buildings to survive. "It's a blow from below that compresses things up, then a shove sideways, and very little can withstand that."
The earth under Canterbury is still shaking out the stress of the fault, with more than 70 aftershocks measured since Tuesday, four of them magnitude 5 or greater. Seismologists said 4000 aftershocks had occurred since the September quake, but now the "clock had been reset" and Cantabrians could expect months more of tremors. Geologists have reported that the liquefaction in the city was worse than during last year's tremor. Many suburbs have seen houses sink into the ground as the shaken soil turns to wet mush.
Somerset Maugham
LARGEST QUAKES -
This morning -
5.4 TONGA
Yesterday -
2/23/11 -
5.3 IZU ISLANDS, JAPAN REGION
5.4 NEAR THE COAST OF NICARAGUA
NEW ZEALAND - Rescuers have given up all hope of finding any more survivors in the rubble of Christchurch's flattened Canterbury TV building where up to 120 people are buried. "At the CTV site there is no chance of survival." Police confirmed that 76 bodies had been brought to the quake-ravaged city's temporary morgue. However, the number of dead from Tuesday's 6.3-magnitude earthquake is expected to skyrocket once recovery efforts get under way in coming days. 238 people are still unaccounted for.
The last person brought out alive was a woman who was pulled from the Pyne Gould Corporation (PGC) building at 3pm (1pm AEDT) yesterday. The PGC building remained a rescue site but police were unable to say how many people were believed to trapped inside. Twenty-nine people have been rescued from the site since the earthquake struck. The badly damaged Christ Church Cathedral contains 16-22 bodies, but the landmark building has been deemed too dangerous to clear. At least three people had died when the bus they were in was crushed by falling rocks. There were also several deaths in cars. Engineers were closely monitoring the 26-storey Grand Chancellor hotel, which is tilting to one side and sunk one-and-a-half metres.
VOLCANOES -
Scientists say volcanoes produce distinctive tremors (persistent earthquakes called volcanic tremors) minutes, days or even weeks before they erupt, making prediction of events possible.
Child dies under volcanic ash cloud in Philippines - Health authorities handed out face masks to thousands of residents around an erupting volcano on Wednesday after a child died of an asthma attack blamed on falling ash. Bulusan volcano spewed a huge ash column on Monday, sending thousands of people fleeing their homes. More than 700 remained at evacuation centres Wednesday awaiting advice on when it is safe to return. Some 6,000 dust masks were handed out to residents of Irosin, one of three towns affected by the ashfall, including nearly 500 people at an evacuation centre there. The health ministry meanwhile distributed face masks in the nearby town of Bulan, where the two-year-old boy died.
Volcanic ash can cause nose, throat, eye and skin irritation as well as contaminate tap water, while prolonged exposure can cause lung disease. Government volcanologists said they had recorded one volcanic quake in the volcano in the past 24 hours, but thick clouds hampered visual observations of further steam and ash emissions.
Bulusan is among 23 active volcanoes in the Philippines, which is located in the so-called Ring of Fire of volcanic activity around the Pacific. Bulusan, 360 kilometres southeast of Manila, last erupted between March and June of 2006. The volcano also shot ash into the air in November last year, forcing hundreds of people to evacuate their homes. However volcanologists said that was not an eruption, but heated ash deposits near the crater mouth that exploded and burst out on contact with rainwater.
Philippine scientists on Tuesday warned of more explosions from the restive Bulusan volcano that has been spewing ash for two days after nearly three months of inactivity.
TROPICAL STORMS -
Cyclone ATU was 421 nmi NE of Auckland, New Zealand
Cyclone CARLOS was 567 nmi NNW of Perth, Australia
AUSTRALIA'S avocado industry has felt the full force of Cyclone Yasi, with the storm destroying fruit worth at least $10 million. About 20 per cent of the crop in north Queensland was stripped from trees and a further 30 to 40 per cent of the fruit was damaged by wind resulting in blemishes to the skin. And with the spotty fruit due to hit supermarket shelves this week growers are assuring consumers the damage is only skin deep. Consumers can help avocado growers get back on their feet by continuing to buy the fruit "despite their imperfect appearance." Both Woolworths and Coles have shown their support for Queensland's growers by reviewing their quality specifications and allowing some spotted fruit to shelf. "Supermarkets will continue to enforce strict quality control on all fruit and vegetables, ensuring any imperfections lie on the surface of the skin only."
The full extent of Cyclone Yasi's damage will be revealed this week as growers begin to harvest their crops. Cyclone Yasi has predominantly affected growers in the north Queensland region, in particular the Atherton Tablelands which accounts for 17 per cent to the nation's overall avocado supply. During March and April this figure jumps to 80 to 85 per cent. It will take about 12 months for the industry to recover and for supplies to return to normal, with suppliers relying on avocados from Bundaberg and Western Australia in the meantime. Consumers can expect to see an improvement in the appearance of the fruit when Bundaberg growers harvest their crop in April.
The outer bands of Severe Tropical Cyclone Atu were spreading above the upper North Island of New Zealand last evening creating a hazy sky. The cyclone is as wide as New Zealand is long and it dwarfs the North Island as it begins its three day trek past the country. Atu is not going to hit New Zealand with all forecasters and models agreeing it will pass well to the east of the North Island. Information on the system is sketchy at this latitude, as it leaves the Fijian authorities and moves into MetService's area of responsibility. However unlike Australia and Fiji, New Zealand's government forecaster doesn't provide tracking or specific maps and updates on tropical systems outside of their marine forecasts and normal weather charts. WeatherWatch.co.nz instead turns to the Joint Typhoon Warning Centre in Hawaii for the latest information. The JTWC says winds this evening are expected to be averaging 150km/h and gusting to 185km/h. As of 7pm NZT the cyclone was centred 800kms north east of Cape Reinga and 1000kms north of East Cape.
Atu will tonight start the process of becoming extra-tropical, which means it loses it's warm centre and starts to develop into a more "typical" low that we'd see around New Zealand. However it still remains a serious storm that will drive in big seas to the east coast of the North Island. It's likely to bring showers to East Cape as well later today or Friday.
