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<DIV><FONT size=4>Why the Chile quake tsunami was smaller than feared</FONT>
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<DIV>by <A
href="http://www.newscientist.com/search?rbauthors=Kate+Ravilious"><B><FONT
color=#000000>Kate Ravilious</FONT></B></A> </DIV>
<DIV>01 March 2010</DIV>
<DIV><A
href="http://www.newscientist.com/article/dn18588-why-the-chile-quake-tsunami-was-smaller-than-feared.html?DCMP=NLC-nletter&nsref=dn18588"><FONT
color=#000000>http://www.newscientist.com/article/dn18588-why-the-chile-quake-tsunami-was-smaller-than-feared.html?DCMP=NLC-nletter&nsref=dn18588</FONT></A></DIV><!-- pgtop -->
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<P class=infuse>The earthquake in Chile on Saturday was one of the biggest the
world has felt in the past century – so why was the tsunami that spread across
the Pacific smaller than originally feared?</P>
<P class=infuse>The magnitude-8.8 earthquake was devastating, claiming at least
700 lives. Large tsunami waves were reported along parts of Chile's coastline:
reports suggest the town of Constitución was worst affected by the wave.</P>
<P class=infuse>Yet locations further afield were more or less spared by the
tsunami. Waves smaller than 1.5 metres struck Hawaii and Japan, for
example, causing very little damage. By contrast, a magnitude-9.5 earthquake in
1960 spawned a tsunami that claimed over 200 lives in Japan, Hawaii and the
Philippines.</P>
<P class=infuse><A href="http://www.soes.soton.ac.uk/staff/then/" target=ns>Tim
Henstock</A> of the National Oceanography Centre at the University of
Southampton, UK, speculates that <U>the reason might be that Saturday's
earthquake ruptured a relatively small segment of fault – around
350 kilometres. The length of fault rupture determines the distance at
which a tsunami begins to lose energy. By comparison, the magnitude-9.1
earthquake that generated the 2004 Indian ocean tsunami ruptured around
1600 kilometres of fault.</U></P>
<P class=infuse><U>Chile's recent tsunami was also highly focused.</U> "It was
quite a directed tsunami, rather than a 'stone in a pool' type propagation,"
explains <A
href="http://www3.newport.ac.uk/displayPage.aspx?object_id=8076&type=SEC"
target=ns>Simon Haslett</A> of the University of Wales, Newport. The tsunami was
severe at the coast nearest the epicentre, and westward at the Juan Fernandez
Islands, but the energy and height were lost quickly in other directions, he
says.</P>
<P class=infuse>Furthermore, the relatively deep origin of the earthquake –
35 kilometres – may have minimised the uplift on the sea floor that
displaced the water. "The Chile quake was smaller and deeper than the Indian
Ocean quake of 2004, so less energy was released and, most importantly, less of
this reached the surface," says <A
href="http://www.abuhrc.org/newsmedia/Pages/affiliate_view.aspx?affiliate=11"
target=ns>Bill McGuire</A> of University College
London.</P></DIV></DIV></DIV></FONT></BODY></HTML>