Surface displacement of the March 26, 1997 Kagoshima-kenhokuseibu earthquake in Japan from synthetic aperture radar interferometry

A JERS 1 differential L-band synthetic aperture radar (SAR) interferogram of the March 26, 1997 Kagoshimaken-hokuseibu earthquake (M-w=6.1) in southwestern Japan shows about 9 cm peak-to-peak coseismic surface displacement in the radar line-of-sight (LOS) direction. A permanent GPS array detected 1 to 2 cm horizontal displacements from this earthquake. By inverting the SAR and GPS data together, we estimated a fault mechanism without any seismological data. A theoretical radar LOS displacement pattern from a single fault model of the earthquake motion matches the SAR and GPS observations closely. The model assumes left lateral slip of 0.46 cm with rake angle of 19 degrees on a rectangular fault plane of dimensions 11 km (width) by 12 km (length). We demonstrate that L-band SAR interferometry can describe several cm surface displacement in detail and construct a fault model. However, despite the acquisitions being during the cold season, there are apparent water vapor signatures in the interferogram with equivalent path delays of up to 1.5 cm.