Jean-Philippe Avouac photoJean-Philippe Avouac Professor of Geology:Director of the Tectonics Observatory:CaltechCaltech logo



Measuring Deformation from Satellite Images and Aerial Photos

After the Landers earthquake it became evident that co-seismic deformation and possibly interseismic deformation can be measured from SAR interferometry. With Rémi Michel and Jean Taboury (Ecole Supérieure d’Optique) we have tested the possibility of measuring  horizontal offsets using SAR amplitude images. The technique proved very efficacious [Michel et al., 1999a] and can be used to improve SAR interferograms, especially in the near-fault zone where coherence is often lost [Michel et al., 1999b]. Following earlier investigations by Bob Crippen, we have next tested the possibility of a similar approach using optical images.

The technique is based on a sub-pixel correlation technique [Van Puymbroeck et al., 2000]. Mis-registration due to stereoscopic effects are compensated together with those due to the changing attitude of the satellite during image acquisition. Residual mis-registrations then reflect ground deformation. Applied to SPOT panchromatic images, the technique provides independent measurements about every 1km with an accuracy of about 0.5m. As shown in the case of the 1999, Izmit earthquake, in Turkey, [Michel and Avouac, 2002] or the Chichi earthquake in Taiwan [Dominguez , Avouac and Michel, 2002], the displacement field obtained from this technique can be used to map co-seismic ground ruptures  and measure slip on the fault. This technique is a valuable complement to SAR interferometry which provides accurate measurements kilometers away from the faults but generally fails in the near-fault zone where the fringes get noisy and saturated. The advent of higher resolution optical imagery, available commercially, makes this approach very promising and applicable to a wider range of magnitude. This technique could be used on an operational basis in the near future to provide rapid information on major earthquakes and help assess source parameters and damages.

We are currently working on improving the technique, in particular, by taking into account some models of the satellite changing attitude (PhD project of Sebastien Leprince).

·        Measuring offsets from SAR amplitudes images [Michel et al., 1999a].

·        Combining SAR interferometry and SAR offsets [Michel et al., 1999b]

·        Measuring offsets from SPOT images , application to Landers (California) [Van Puymbroeck et al., 2000]. See fig. 1.


                                Figure 1 - Amplitude of co-seismic displacements measured from SPOT images.

·       Application to Izmit ( Turkey ) [Michel and Avouac,  2002]. See fig 2.


                        Figure 2 -  Co-seismic displacements measured from SPOT images.

·        Application to Chichi (Taiwan) [Dominguez, Avouac and Michel, 2002].  See fig. 3.


Figure 3 - Amplitude of ground displacements measured from SPOT images. Ground displacements measured from GPS and SPOT images.

SAR interferometry on the 1995  the Aqaba earthquake [Klinger, Michel and Avouac, 2000].

My main contributions on the subject:

Leprince, S., P. Muse, J.P. Avouac, In-Flight CCD Distortion Calibration for Pushbroom Satellites Based on Subpixel Correlation, IEEE Transactions on Geoscience and Remote Sensing, 46, No. 9, 2008. [PDF]

Dominguez  S., J.P. Avouac, 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, Journal of Geophysical Research, 108, 2003 . [PDF]

Klinger, Y., R. Michel and J.P. Avouac, Co-seismic deformation during the Mw 7.3 Aqaba earthquake (1995):  from ERS-SAR interferometry , Geophys. Res. Lett., 27, 3651-3654, 2000. [PDF]

Michel, R.,  J.P. Avouac, and J. Taboury, Measuring ground displacements from SAR amplitude images : Application to the Landers earthquake, Geophys. Res. Lett., 26, 875-878, 1999a. [PDF].

Michel, R.,  J.P. Avouac, and J. Taboury, Measuring near field coseismic displacements from SAR images : Application to the Landers earthquake, Geophys. Res. Lett., 26, 3017-3020, 1999b. [PDF]

Michel, R. and J.P. Avouac,  Deformation due to the 17 August Izmit, Turkey, earthquake measured from SPOT images, J. Geophys. Res, 107, 2002. [PDF]

Van Puymbroeck, N., Michel, R., Binet, R., Avouac, J.P. and J. Taboury. Measuring earthquakes from optical satellite images, Applied Optics Information Processing, 39 (20): 1–14, 2000.  [PDF]

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