Abstract:

Space-borne Interferometric Synthetic Aperture Radar (InSAR) techniques provide a method to determine earthquake locations and focal mechanisms that are independent of error sources which have plagued seismologists for the last century, including: inaccurate velocity models, sparse and uneven station coverage, and inaccurate or misidentified phase picks. By modeling InSAR-derived surface deformations, the rupture plane and fault slip of near-surface dry-land events can be obtained. The prospect of a dedicated InSAR mission, combined with the now-refined processing techniques, makes routine seismic monitoring using InSAR a future possibility. Here we assess the potential impact of InSAR on routine earthquake analysis by estimating the frequency and global distribution of InSAR-detectable earthquakes. Theoretical detection-threshold curves for a range of magnitudes, focal mechanisms, and depths show which earthquakes are candidates for InSAR analysis. These calculations indicate that earthquakes smaller than 4.5 are unlikely to produce sufficient surface deformation for the extraction of source parameters, assuming a threshold of 3 cm line-of-sight displacement. Good locations and mechanisms can likely be obtained from magnitude 5.5, 6.0, and 6.5 earthquakes occurring beneath land areas with depths less than 5 km, 15 km, and 30 km respectively. We estimate about 30 near-surface earthquakes per year will produce enough surface deformation for InSAR analysis. However even with a dedicated InSAR mission, some earthquakes will be unusable due to interferometric phase decorrelation. Thirty earthquakes is only a small fraction of the ~1,000 moderate and larger (Mw >= 5.0) earthquakes that occur globally per year. However, near-surface earthquakes occurring beneath land commonly have great societal impact. In addition, InSAR promises accurate locations in seismogenic areas with sparse regional seismic-station coverage, such as southern and western China, New Guinea, Kamchatka, Iran, and some regions of western South America.