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

Abstract

[1] The 1999 Chi-Chi earthquake, M w = 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 5-6 m near the epicenter to 10-11 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 20-35°east dipping ramp, which soles out into a low dipping décollement 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 5-6 m in the south to 7 to 12 m to the north. Our model suggests that the deeper portion of the fault was not activated during the Chi-Chi earthquake. This zone of slip deficit must break during large earthquakes or be activated during transient episodes of aseismic slip. On the basis of these observations, the western front of the central Taiwan should produce a M = 7 to 7.5 event, about every 150 to 250 years.INDEX TERMS: 8040 Structural Geology: Remote sensing; 7209 Seismology: Earthquake dynamics and mechanics; 7230 Seismology: Seismicity and seismotectonics; 7260 Seismology: Theory and modeling; KEYWORDS: earthquake, Chi-Chi, Taiwan, coseismic, imagery, Okada Citation: Dominguez, S., J.-P. Avouac, and R. Michel, 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,

Monitoring Earth Surface Dynamics With Optical Imagery

“…Optical-image correlation has proven to be effi cient in mapping fault ruptures and in measuring both the faultparallel and fault-perpendicular components of coseismic displacements [Avouac et al, 2006]. Several studies indicate success in correlating images from the same sensor and with nearly equal incidence views [e.g., Van Puymbroeck et al, 2000;Dominguez et al, 2003;Klinger et al, 2006]. COSI-Corr now allows the processing of images acquired by different systems and with different incidence views, considerably broadening the technique's potential.…”

Co-Registration of Optically Sensed Images and Correlation (COSI-Corr): an operational methodology for ground deformation measurements

“…In principle, this information can be retrieved from sub-pixel correlation of pre-and post-earthquake remotely sensed optical images [1], as illustrated by earlier promising results [2], [3], [4]. However, this technique suffers from numerous limitations, mostly due to uncertainties on the imaging systems and on the platform attitudes.…”

Coseismic displacements of the 14 November 2016 <i>M</i><sub>w</sub> 7.8 Kaikoura, New Zealand, earthquake using the Planet optical cubesat constellation

“…These methods can be combined (e.g. Fialko et al, 2001). Typical revisit times for current radar satellites are of the order of a few days to weeks (e.g.…”

“…Coseismic displacements have, for instance, been measured on repeat data from Landsat (Liu et al, 2006;Avouac et al, 2014;Barnhart et al, 2014), ASTER , SPOT (Dominguez et al, 2003;Leprince et al, 2007;Konca et al, 2010), very high-resolution optical satellites (Barnhart et al, 2015;Zhou et al, 2015), or air photos (Michel and Avouac, 2006;Ayoub et al, 2009). Coseismic displacements from Sentinel-2 data have to our best knowledge not yet been published in peer-reviewed journal publications, but are used by operational services (COMET, 2016).…”