HR: 0800h
AN: T41B-1301    [Abstracts]
TI: Co-seismic Horizontal Ground Slips of 1999 Chi-Chi Earthquake (Mw 7.6) Deduced From Image-Comparison of Satellite SPOT and Aerial Photos
AU: * Kuo, Y
EM: yutingkuo@ntu.edu.tw
AF: Dept. of Geosciences, NTU, Taipei, 106
AU: Ayoub, F
T41B-1301 AF: Division of Geological and Planetary Sciences, Caltech, Pasadena, 91125
AU: Avouac, J
T41B-1301 AF: Division of Geological and Planetary Sciences, Caltech, Pasadena, 91125
AU: Leprince, S
T41B-1301 AF: Division of Geological and Planetary Sciences, Caltech, Pasadena, 91125
AU: Chen, Y
EM: ygchen@ntu.edu.tw
AF: Division of Geological and Planetary Sciences, Caltech, Pasadena, 91125
AU: Shyu, J H
T41B-1301 AF: Division of Geological and Planetary Sciences, Caltech, Pasadena, 91125
AU: Kuo, Y
T41B-1301 AF: Mathematics Dept., Indiana Univ., Indiana, 15705
AB: In addition to seismological records,the measurement of coseismic ground displacements is critical to understand the mechanism and behavior of seismic rupture.Geodetic measurements,i.e.,GPS or conventional techniques,can provide accurate results but only on a limited number of points.A much more complete measurement of the displacement field can be retrieved from sub-pixel correlation of optical images,such as satellite imagery(i.e.,SPOT,ASTER,IKONOS)or even aerial photos.The established displacement field can be further utilized to analyze fault geometry and slip distribution at depth with unprecedented accuracy.As previously published by Dominguez et al.in 2003,the offsets from SPOT provide a reliable configuration of horizontal coseismic ground slips when compared with the GPS dataset.However,their results still showed inconsistencies with the field observations at specific places.Besides,this former study did not apply to the southernmost segment.By using an improved method,we attempt to find solutions for the above-mentioned inconsistencies and to complete the mapping of the southernmost segment.In addition to SPOT,aerial photos in the central segment near Tsaotun are processed to test the method at high resolution,as subsidiary structures were recognized in the field,in particular a back-thrust.Regardless the source imagery,all images are orthorectified by taking Ground Control Points (GCP) away from the fault trace or close to GPS stations.Each SPOT image covers an area of 60 x 60 km with a ground resolution of 10 m, whereas one aerial photo covers an area of 2 x 2km and with a resolution of 0.5 m.New SPOT results yield:(1)better consistency regarding to the previous discrepancies;(2)complete surface rupture pattern in southernmost segment where field investigation is hard to accomplish due to the mountainous terrane.Furthermore, our results confirm that a proposed triple junction model in 2002 is a way of stress-transfer in the southern end of 1999 surface rupture.On the other hand, results from aerial photos provide consistent measures with SPOT but with a higher resolution,and appear to show the secondary structures such as a back-thrust recognized in the field before.
DE: 8000 STRUCTURAL GEOLOGY
DE: 8040 Remote sensing
SC: Tectonophysics [T]
MN: Fall Meeting 2005