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When Asteroids Hit...

Read an interesting article in BBC News 'Science' section this evening. Could We Survive An Asteroid Hit? looks at the impact, destruction and aftermath of an asteroid hitting the center of  London. The figures are based upon previous strikes against our little planet and scientific calculations. Scientists at the University of Arizona have even developed a website so you can calculate the effects of an asteroid strike near you. It's called the Earth Impact Effects Program but I'd recommend reading the BBC article before trying it out (unless you're a scientist in which case you'll understand the jargon already).

I checked out my survival rate if an asteroid hit the center of London (about 6 miles from where I live) and ignoring the radiation effects I got the following if we're hit by a standard 'one in every 1,000 years' asteroids...


The major seismic shaking will arrive at approximately 1.9 seconds.

Richter Scale Magnitude: 5.4
Mercalli Scale Intensity at a distance of 9.66 km:

VI. Felt by all. Many frightened and run outdoors. Persons walk unsteadily. Windows, dishes, glassware broken. Knickknacks, books, etc., off shelves. Pictures off walls. Furniture moved or overturned. Weak plaster and masonry D cracked. Small bells ring (church, school). Trees, bushes shaken (visibly, or heard to rustle).

VII. Difficult to stand. Noticed by drivers of motor cars. Hanging objects quiver. Furniture broken. Damage to masonry D, including cracks. Weak chimneys broken at roof line. Fall of plaster, loose bricks, stones, tiles, cornices (also unbraced parapets and architectural ornaments). Some cracks in masonry C. Waves on ponds; water turbid with mud. Small slides and caving in along sand or gravel banks. Large bells ring. Concrete irrigation ditches damaged.

Masonry C. Ordinary workmanship and mortar; no extreme weaknesses like failing to tie in at corners, but neither reinforced nor designed against horizontal forces.
Masonry D. Weak materials, such as adobe; poor mortar; low standards of workmanship; weak horizontally.


The air blast will arrive at approximately 32.2 seconds.

Peak Overpressure: 51256.1 Pa = 0.5126 bars = 7.2784 psi
Max wind velocity: 91.5 m/s = 204.8 mph
Sound Intensity: 94 dB (May cause ear pain)
Damage Description:

    Multistory wall-bearing buildings will collapse.

    Wood frame buildings will almost completely collapse.

    Glass windows will shatter.

    Up to 90 percent of trees blown down; remainder stripped of branches and leaves.
    Sounds like fun for me!


( 2 comments — Leave a comment )
Apr. 13th, 2004 06:12 pm (UTC)
At least you only get blown off your feet and have to dodge flying trees.
The poor sods around Soho would be vapourised where they stand.
Apr. 13th, 2004 07:06 pm (UTC)
That's nothing. I've been dropping the moon on the UK (not out of malice mind you, I just wanted to see what the effects on me here on Vancouver Island would be). According to the website, I'd be buried under the ejecta even though I'm about 5,000 km away, and the earthquake would be somewhere around magnitude 16 :)

I'm fairly desensitized to these things though. I think what people should be more worried about is the fact that there are very few astronomers looking for asteroids that could hit us - it's still a very underfunded side of the field, and as you can see from that website it's very necessary - if the Tunguska event (a rocky body that blew up over Siberia in 1908) had happened over a major city, millions would have been killed.
( 2 comments — Leave a comment )

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