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Rupture characteristics of the 2003 Mw 7.6 mid-Indian Ocean earthquake: Implications for seismic properties of young
 

Summary: Rupture characteristics of the 2003 Mw 7.6 mid-Indian Ocean
earthquake: Implications for seismic properties of young
oceanic lithosphere
Michael Antolik,1,2
Rachel E. Abercrombie,3
Jianfeng Pan,1
and Go¨ran Ekstro¨m1
Received 16 April 2005; revised 12 October 2005; accepted 20 December 2005; published 13 April 2006.
[1] Analysis of broadband seismograms from the 15 July 2003 large earthquake (M 7.6)
in the central Indian Ocean reveals an unusual source process. The source duration of
longer than a minute is more than twice as long as expected from earthquake scaling
relations, yet $80% of the moment release occurred in two energetic asperities near the
end of the rupture. These two asperities were located in lithosphere with an age of 7 Ma or
greater. A previous study has suggested that strike-slip earthquakes in oceanic lithosphere
having much longer than expected source durations also have a slow, dissipative
rupture process characterized by low radiated seismic energy (and therefore low apparent
stress). We find no evidence for a slow rupture process to the 2003 earthquake. Instead, the
long duration appears to be due only to nucleation close to the actively spreading Carlsberg
Ridge, in lithosphere younger than 7 Ma. Younger oceanic lithosphere may be able to
generate small to moderate earthquakes but be unable to sustain slip in a large event due to

  

Source: Abercrombie, Rachel E. - Department of Earth Sciences, Boston University

 

Collections: Geosciences