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Horizontal coseismic deformation of the 1999 Chi-Chi earthquake measured from SPOT satellite images: Implications for the seismic
 

Summary: Horizontal coseismic deformation of the 1999 Chi-Chi earthquake
measured from SPOT satellite images: Implications for the seismic
cycle along the western foothills of central Taiwan
Ste´phane Dominguez, Jean-Philippe Avouac,1,2
and Re´mi Michel
Laboratoire de De´tection et de Ge´ophysique, Commissariat a` l'Energie Atomique, Bruye`res-le-Cha^tel, France
Received 6 August 2001; revised 8 April 2002; accepted 9 September 2002; published 7 February 2003.
[1] The 1999 Chi-Chi earthquake, Mw = 7.6, broke a major thrust fault along the western
foothills of the Central Range of Taiwan. We have measured the horizontal coseismic
displacement field by correlating optical satellite images acquired before and after the
earthquake. These data reveal the fault trace and a clockwise rotation of surface
displacements toward the north with much larger displacements and strain in the hanging
wall. At the surface, coseismic slip increases from 5­6 m near the epicenter to 10­11 m
to the north. In the epicentral area, we observe a left-lateral strike-slip zone trending
N125°E, and farther north, a fault zone trending N-S with a right-lateral component. The
data were modeled using elastic dislocations. The fault geometry consists of a shallow
20­35° east dipping ramp, which soles out into a low dipping de´collement at a depth of
$6 to 8 km. Surface displacements can be satisfactorily modeled, assuming a constant
slip azimuth on the main fault plane, close to the azimuth of plate convergence (N305°E ±
5°). At depth, slips along the fault plane evolve from 5­6 m in the south to 7 to 12 m

  

Source: Avouac, Jean-Philippe - Division of Geological and Planetary Sciences, California Institute of Technology
Heaton, Thomas H. - Division of Geological and Planetary Sciences, California Institute of Technology

 

Collections: Engineering; Geosciences