Dan,

As the number of stations decreases and their spacing increases, the 
resolution of the process decreases proportionally.  If you want to 
record good detail you need lots of close-spaced stations.  For 
example, if there had been a less dense array, the details of the 
Sendai quake would have been more fuzzy, and less accurate.  So the 
plan for the USArray has been to have a limited geographical area for 
the Transportable Array and every so often roll it toward the 
East.  That way they can get a detailed look at what the earth is 
like under and around the US, in particular, while only requiring 
about 1/10 as many instruments.  Their Web 
site,    http://www.usarray.org/    tells the story much better than I can.

Regards,
Brett

At 10:11 AM 3/16/2011, Dan Bolser wrote:
>Cheers Brett,
>
>Indeed that visualization is incredibly cool, but I'm still not
>getting my head round the argument.
>
>Let me try again (I'm really sorry if this is coming over as trolling,
>I'm just trying to understand properly): If I were to force you at
>gunpoint to close one of those stations (from the YouTube
>visualization) wouldn't you be more willing to close one in the middle
>of the array rather than one scattered around?
>
>If I forced you to close 50 stations, wouldn't you just thin out the
>array in certain places rather than removing all the scattered
>stations?
>
>Perhaps I'm getting it wrong, and you would choose to keep the array
>intact, and selectively remove the 'outliers'. I'd be interested to
>know.
>
>
>Thanks again for the links to the very nice images.
>Dan.
>
>P.S. I'm not proposing that we should close any stations! I'm just
>wondering if I can use much less data to represent most of the
>'information'. This is a concept from bioinformatics, where you can
>trim a protein sequence database to 10% of its original size, yet keep
>90% accuracy in terms of protein family identification of a query
>sequence [1].
>
>[1] http://www.ncbi.nlm.nih.gov/pubmed/10871268


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