Geoscience Journal Vol. 2, No. 2, p. 78--87, June 1998 Feasibility of applying space-borne SAR interferometry for earthquake tectonic investigation Wooil M. Moon John Ristau Paris Vachon Geophysics, University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada (e-mail: wmoon@cc.umanitoba.ca) Applications Division, Canada Center for Remote Sensing, Ottawa, Ontario K1A OY7, Canada ABSTRACT: Space-borne Synthetic Aperture Radar (SAR) techniques have recently become one of the most flexible and cost-effective Earth-observation tools for monitoring surface processes, including natural hazard monitoring and man- agement tasks such as landslides, volcanic activities, and earth- quake-related problems. This study investigates the feasibility of applying space-borne SAR interferometry to the monitoring of earthquake hazards and investigation of the earthquake- related tectonic processes, focusing on the investigation of the geological setting and associated tectonic processes in the Na- hanni Earthquake area, NWT, Canada. Investigation of seismotectonics in the Nahanni area was carried out in two stages: traditional analysis of remote-sensing data, including both optical and microwave data, for static aspects of tectonic processes (Moon et al., 1991); and new SAR interferometry using RADARSAT, ERS-1/2, and JERS-1 SAR data to study relative movements of several active geological tectonic blocks. Preliminary results indicate that (1) conventional geological remote-sensing methods provide us with important basic infor- mation on the tectonic setting associated with local earthquake activities, including several newly discovered structural fea- tures, and remain important as Earth-observation tools, (2) the newly discovered tectonic features correlate well with the earthquake focal plane solutions obtained from teleseismic data, (3) multi-temporal SAR interferometric (or differential InSAR) analysis can provide us with detailed tectonic movements and understanding of the earthquake processes in the study area, but (4) availability of suitable space-borne SAR data suitable for differential SAR interferometry may pose more problems than the technical development. Key words: SAR interferometry, earthquake tectonics, RADARSAT, geological remote sensing 1. INTRODUCTION Theoretical and laboratory simulation of optical inter- ferometry and holographic intefferometry techniques were proposed and developed in the 1960"s (Gabor et al., 1965; Hilderbrand and Haines, 1967). However, it was the pio- neering work by Graham (1974) that demonstrated that microwave synthetic aperture radar (SAR) interferometry was a viable technique for the derivation of digital terrain models and related applications. More recent works have greatly extended the technological basis and application capabilities of both airborne and space-bome interferome- tric SAR (Zebker and Goldstein, 1986; Goldstein et al., 1988; Prati et al., 1989; Li and Goldstein, 1990; Zebker and Villasenor, 1992; Massonnet and Rabaute, 1993; Gray et al., 1994; Ishikawa et al., 1994; Massonnet et al., 1994; Stevens et al., 1994). The application of radar interferometry to topographic mapping was first successfully implemented by Graham (1974), and was followed by Zebker and Goldstein (1986), Gabriel and Goldstein (1988), Goldstein et al. (1988), and Gabriel et al. (1989). Airborne SAR interferometric tech- niques were studied and successfully tested by Gray and Farris-Manning (1993), Stevens et al. (1994), Gray et al. (1994), and his group at the Canada Center for Remote Sensing (CCRS). Airborne interferometric SAR (or inSAR) techniques were also developed by several Japanese scientists including Ishikawa et al. (1994). Realistic multi- baseline SAR interferometry was successfully developed and tested using SEASAT (L-Band) SAR data over Death Valley, California by Li and Goldstein (1990). Their work is important because they tested several para- meters for space-borne repeat orbit interferometric tech- niques. They also defined an "optimal baseline separation" for the maximum surface-height accuracy for a given sys- tem configuration. Massonnet and Rabaute (1993) and Massonnet et al. (1994) reported the first successful differential interfero- metric SAR imaging of the displacement field of the earthquake in Landers, California using the ERS-1 SAR system. According to Massonnet and his group (personal communication), sub-centimeter accuracy can now be achieved using intefferometric SAR if optimum con- ditions can be met. Even though the basic principle of SAR intefferometry is the invariant, the actual approach and implementation of obtaining topographic interfer- ograms are different between the JPL (e.g., Zebker and Goldstein, 1986; Zebker and Villasenor, 1992) group and the Massonnet (CNES, France) group. In this research, we initially planned to thoroughly review both approach- es and develop an optimum algorithm for a selected modes of RADARSAT and compare the results with