For those in the Tokyo metropolitan area, one of the scariest prospects is for a so-called shuto chokka-gata quake of the magnitude 8 class, which last occurred in 1703. Chokka means "directly beneath," but this does not mean such a quake's epicenter would necessarily be under the center of Tokyo, but rather somewhere within a large area that ranges between southern Ibaraki in the northeast to Kanagawa's boundary with Shizuoka in the southwest. Since 1894, five large quakes ranging from magnitude 6.7 to magnitude 7.2, have occurred therein, with the epicenter of two in Ibaraki (1895 and 1921), one in Tokyo (1894), one off the coast of Chiba (1987) and one near the entrance to Tokyo Bay (1922).
Guessing where the next one will strike is like playing Russian roulette with a revolver with chambers for 18 bullets. On a list drawn up by the Cabinet Office in 2005, each scenario contains an estimate of human fatalities and number of structures suffering damage. Quakes between magnitude 6.9 and 7.3 centered at the north, east, or west of Tokyo Bay, for example, are projected to kill between 11,000 and 12,000 people and damage or destroy some 680,000 to 850,000 buildings. These three, however, are worst-case scenarios and the damage from a quake occurring on the region's outer fringes would be much less. In any event, havoc is likely to ensue. A scenario of what could be expected to transpire in Tokyo in the first week following a major earthquake points out that 70 percent of Tokyo's water mains are unprepared for a major quake. Repair costs to water mains from a Tokyo quake of the same scale as the one last March 11 would run several tenfolds that of the damage incurred in Tohoku. And the power utility may need as long as 55 days to restore electric power to 1.9 million households.
As for harbingers of impending geological activity, reportsare coming in that bats in caves at the foothills of Mt. Fuji have begun to behave erratically since last December. Are their sensitive ears picking up the nascent rumbles of a major volcanic eruption? What really drove the needle against the pin on the scare-o-meter was the front page story in the Yomiuri Shimbun of Jan. 23, which cited a team of seismologists at the University of Tokyo who were quoted as having estimated the probability of a major quake beneath Tokyo as 70 percent within the next four years. With such a probability, 'by the time this column is printed, the quake might have already occurred'.
A point of contention arose, however, over the estimate cited by the Todai team, which appears to have been based on analysis of the frequency of aftershocks following the March 11 disaster off the coast of Miyagi Prefecture through September. The number has tapered off sharply since then. The publishing of such figures points to "a decline in the quality of journalism," because the writer cherry-picked the figures without providing other data that mitigates their impact. The newspapers are now even worse than the weekly magazines. Since readership is in decline, their reporters want to run figures that catch readers' attention. Then that gets amplified by TV networks and the weekly magazines. This suggests Japanese journalism is in its final throes of terminal illness." "Stated simply, for each incremental increase in quake magnitude, the number of earthquakes declines to one-tenth. For every 10 magnitude-5 quakes occurring, there will be one magnitude 6. While the total number of earthquakes between March and September of last year were sevenfold that of a normal year, if the number from September is extended through to present, the figure drops to just threefold. So that should make the likelihood of a major quake in Tokyo 80 percent over the next 30 years and less than 50 percent over the next four years."
for it is better to be alone than in bad company.**
George Washington
LARGEST QUAKES -
This morning -
5.4 NORTHERN SUMATRA, INDONESIA
5.0 KYRGYZSTAN
Yesterday -
2/19/12 -
5.3 NEAR EAST COAST OF HONSHU, JAPAN
5.1 FIJI REGION
5.1 CROZET ISLANDS REGION [2006 km (1246 miles) SSE of Mozambique]
Iranian Experts to Manufacture Earthquake Prediction Satellite - Iranian researchers plan to manufacture a law-altitude satellite which helps predict earthquakes from space. The satellite dubbed Ayat (Signs) will help predict the time of earthquakes for the first time in the country. The Deputy Head of Iran's Industrial and Scientific Studies Center for Innovation and International Cooperation said the satellite would identify the signals sent out from the earth before or after the earthquake, adding the satellite weighs 50-70 kg and would be placed in a lower altitude.
He stressed some countries including France, China and Russia are working in this regard, noting Ayat satellite possesses a key role in processing the seismic disturbances before and after the shocks.
Basic studies have been carried out and the practical process will begin after the required budget is provided.
Iran sits astride several major faults in the earth's crust, and is prone to frequent earthquakes, many of which have been devastating. The worst in recent times hit Bam in southeastern Kerman province in December 2003, killing 31,000 people - about a quarter of its population - and destroying the city's ancient mud-built citadel. The deadliest quake in the country was in June 1990 and measured 7.7 on the Richter scale. About 37,000 people were killed and more than 100,000 injured in the northwestern provinces of Gilan and Zanjan. It devastated 27 towns and about 1,870 villages. Tehran alone sits on two major fault lines, and the capital's 14 million residents fear a major quake.
New Zealand - Five thousand earthquakes after the devastating February 22 tremor, Canterbury's aftershock sequence has a recognisable personality. Seismologists looking at 12 months of data have found that the frequency and size of the aftershocks is similar to the seismic aftermath observed in eastern Californian and Tasmanian events, where the tremors lasted decades but were increasingly smaller in scale.
Since the original rumble in September 2010, 10000 quakes have rattled Canterbury. More than 5500 of these have occurred since the deadly February 2011 quake re-energised the sequence, and 214 of these tremors were magnitude 4 or larger. The Darfield aftershock sequence is expected to last for 30 years, with tremors tailing off gradually until they are unnoticeable. Cantabrians repeatedly asked whether they were experiencing a particularly vicious sequence, in particular when a magnitude 5.8 earthquake occurred two days before Christmas. Seismologists say the Darfield sequence was not violent compared with historical records. In contrast, Sumatra is still experiencing moderate-size quakes eight years after the magnitude 9.1 quake which caused the Boxing Day tsunami in 2004.
But unlike the Sumatran sequence, the Canterbury quakes were limited to a smaller geographic area, and have been particularly hard on Christchurch's central city. "We had the misfortune of the quakes migrating into the city and staying in the city for a while. But now we're seeing them migrating away." GNS Science's latest computer modelling shows there is an 8% chance of a 5.5 to 5.9 magnitude tremor in the next month and 2% chance of a magnitude 6 to 6.4 quake.
Why the city suffered so badly -
* 60km to 80km of the earth's crust has experienced a stress change, meaning the aftershock sequence will last about 30 years.
* Horizontal ground motions 1.7 times the force of gravity were larger than expected.
* One reason for this could be the way the fault ruptured towards Christchurch (it had strong "directivity").
* Upper and lower layers of the earth separated during the quake, then "slapped" back together, producing very high impacts (known as the trampoline effect).
* The hard rock under Banks Peninsula may have compounded the effect of the quake by reflecting seismic activity back towards the city.
* There were "remarkably high" levels of stress built up under Canterbury's soil.
* High water tables trapped energy in the top layers of soil in some areas, boosting liquefaction.
* Liquefaction caused the worst damage to land and buildings, including many CBD high-rises.
* Deep-seated landslides caused the most damage in the southern Port Hills.
* Critical structural elements in buildings built between 1976 and 1992 failed.
VOLCANOES -
Alert level raised for a new remote Alaska volcano - The Alaska Volcano Observatory has raised the alert level for Kanaga Volcano in the remote Aleutian Islands. in the remote Aleutian Islands. Scientists on Saturday said possible explosive activity and a likely ash cloud indicate new unrest at the volcano, leading it to raise the volcano alert level from normal to advisory. Volcanic tremor was detected at about 6:23 a.m. Saturday. The unrest indicates a possibility for sudden explosions of ash to occur at any time, and ash clouds exceeding 20,000 feet above sea level may develop. Ash clouds above 20,000 feet from Alaska volcanoes are a threat to trans-Pacific air carriers. Kanaga Volcano is located about 1,215 miles southwest of Anchorage.
TROPICAL STORMS -
In the Indian Ocean -
-Tropical cyclone 12s (Giovanna) was located approximately 455 nm south-southeast of Antananarivo, Madagascar.
-Tropical cyclone 13s was located approximately 650 nm east of Port Louis, Mauritius.
HEAVY SNOW / EXTREME COLD -
U.S. - Deadly avalanche near ski resort in Washington state - 4 dead. A police spokesperson said the skiers were ''very experienced'' and well prepared. Rescuers were dispatched to an out-of-bounds area near Stevens Pass ski resort after reports around noon local time (20:00 GMT). Three were killed and eight skiers declared missing were later accounted for. The resort is located in the Cascade Mountains north-east of Seattle. The Northwest Weather and Avalanche Center warned of a high avalanche danger above 5,000 ft in the Stevens Pass area with a considerable danger at lower levels. The centre said there had been heavy snowfall over the last few days. Another person was killed in a separate incident when a snowboarder went over a cliff at Alpental ski area east of Seattle.
SPACE WEATHER -
AURORAS OVER THE USA - A solar wind stream hit Earth's magnetic field during the waning hours of Saturday, Feb. 18th. Although the stream was expected, the bright auroras it produced were not. Northern Lights spilled across the Canadian border into US states such as Wisconsin, Michigan, Nebraska, North Dakota, Iowa, and Minnesota. In Grand Portage, MN. "For an hour and a half we were treated to a green glow peppered with dancing curtains of green, purple and red." In Nebraska - yes, Nebraska - "I saw auroras on and off for approximately 2 hours from around 9pm to 11pm local time. There was a brief spell where color was visible to the eye with rays and bands."
This episode might have been amplified by the action of a co-rotating interaction region or "CIR." CIRs are transition zones between fast and slow solar wind streams. Solar wind plasma piles up in these regions, producing density gradients and shock waves that do a good job of sparking auroras. Local solar wind data suggest that Earth moved through a CIR around 1500 UT on Feb. 18th. (photos)
