Tuesday, May 20

Chinese experts give reasons for magnitude revision of SW China earthquake

BEIJING, May 19 (Xinhua) -- Experts from the China Seismological Bureau (CSB) said on Monday the magnitude revision of the strong earthquake in southwestern Sichuan Province was due to confirmed statistics from more monitoring stations at home and reference from overseas seismological observatories.

"It is a common practice to revise the magnitude of a major earthquake," said Xiu Jigang, CSB deputy director in an interview with Xinhua.

He explained that scientists had to use statistics from a few monitoring stations to estimate the magnitude of the earthquake as soon as possible. Then as they were able to take reference of statistics from more domestic stations and with the estimated figures by the observatories around the globe, they came to a more accurate conclusion.

The first report by CSB set the magnitude at 7.6 on the Richter scale after the quake hit Sichuan Province on May 12. The quake was shortly upgraded to 7.8. Then the bureau revised the magnitude from 7.8 to 8.0 on Sunday.

The magnitude was revised upward after specialists carried out "real-time and detailed measurements of the quake according to international practices," said Luo Zhuoli, an expert with CSB.

Scientists from the United States first put the magnitude of the tremor at 7.8 and then revised it to 7.9, while their counterparts in Europe revised it from 7.5 to 7.9, and Russia, 8.0.

The quake, claiming 34,073 lives as of 4:30 p.m. Monday and leaving 245,108 injured so far, has caused serious damage to buildings, bridges and other public facilities in an area of more than 100,000 square kilometers.

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Comet Boattini: Barely Visible Now, Bright in July?

Serious comet chasers — people who track faint comets with telescopes and binoculars — have been aware of Comet C/2007 W1 (Boattini) for quite a while. It was forecast to become quite bright for a telescopic comet, 6th or perhaps even 5th magnitude, making it visible without optical aid to skilled observers at dark sites.

So far, Boattini has exceeded the brightness predictions by more than a full magnitude. If it keeps behaving like this — and that's a very big if! — it could become quite prominent in July.

Right now, unfortunately, the comet is fairly deep in the southern sky, making it a difficult target from mid-northern latitudes. The best sightings have been from the Southern Hemisphere, where it's already visible without optical aid under ideal conditions. But Boattini has also been spotted by many binocular observers in the southern tier of the United States, particularly Arizona and Southern California.

At the time of writing, the nearly full Moon makes Comet Boattini's faint, fuzzy shape almost impossible to see. But there will be a brief window of visibility after the Moon gets out of the early-evening sky (on May 21st) and before the comet disappears into the Sun's glow in June.

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