[meteorite-list] falls per year

From: Michel <Michel_at_meteoritecentral.com>
Date: Thu Apr 22 09:41:13 2004
Message-ID: <005101c0a1a8$b1af3080$0100a8c0_at_nwc.fr>

Hello Jeff and List,

How many is THE QUESTION and so often asked that we came last week to talk
about it with Claude PERRON, in charge of the Lab when Brigitte Zanda is the
US.

he gave me teh following figures:

Between 10 000 and 50 000 falls per year of meteeorites weighing more than
20 grams.
Another figure is 100 falls over 100 kg per year.
Above figures are ocean included.

Your analysis makes sense but there is a unknown factor ( you said it is
0.30) but this a very difficult factor to estimate. I personnaly think that
this factor can be influenced by the following:

density of population. coef increases with density
annual earning ( the more you earn the less you live outside) coef decreases
with earning
average vegetation height coef decreases with height.

Best wishes

Michel FRANCO


.


Michel FRANCO
100 Chemin des Campènes
74400 CHAMONIX - FRANCE
----- Message d'origine -----
De : Jeff Grossman <jgrossman_at_usgs.gov>
À : <meteorite-list_at_meteoritecentral.com>
Envoyé : mercredi 28 février 2001 14:59
Objet : [meteorite-list] falls per year


> Here's a fresh estimate of the number of RECOVERABLE meteorite falls on
the
> earth each year. I don't know what the other workers have done, but this
> is a fairly simple way to get a minimum estimate:
>
> The most densely populated places on earth have the highest recovery rates
> of meteorite falls. One such place is Japan. Over the last 20 years of
> the 20th century, 10 falls were recovered there: Aomori, Tomiya,
Kokubunji,
> Tahara, Mihonoseki, Senboku, Neagari, Tsukuba, Kobe, and Sayama. The rate
> was almost as high (9 meteorites) between 1920 and 1940, so this is not an
> anomalous statistic. The surface area of Japan is 3.73e5 km^2, but
nothing
> is ever recovered on sparsely populated Hokkaido, so the effective area
for
> this calculation is 2.94e5 km^2. We can now calculate the number of falls
> per year per km^2, and then extrapolate this to the surface of the entire
> earth (5.12e8 km^2). Assuming my numbers are right for all these areas,
we
> get 870 falls/year on earth, which we can take as a lower limit on the
true
> value.
>
> This calculation assumes that the Japanese are 100% efficient at
recovering
> all falls in the country, which is not likely. Adding another fudge
factor
> for this which I'll conservatively place at 0.3 (30% efficiency), we get
an
> adjusted figure of 2900 falls/year on earth. If 70% of the earth is
ocean,
> we get a figure of 870 falls/year just on land.
>
> There is no object-size limit on this calculation, it's just based on
> recoverable falls. Obviously it is biased toward bigger things.
> Dr. Jeffrey N. Grossman phone: (703) 648-6184
> US Geological Survey fax: (703) 648-6383
> 954 National Center
> Reston, VA 20192, USA
>
>
>
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Received on Wed 28 Feb 2001 11:53:28 AM PST