A simple method for improving the resolution of geodetic slip inversion

SUMMARY In geodetic slip inversions, resolution decreases rapidly with depth because deformation data are measured at the ground surface. Traditionally, this decrease in resolution has been attributed to the weak deformation signals caused by slips at greater depths. However, this study demonstrated that the primary cause is the stronger smoothing applied to deeper slips compared to shallower ones. This work proposes a method that scales the Green's functions to equalize smoothing effects across depths. The method's effectiveness was validated through both synthetic tests and real earthquake applications. In synthetic tests, it improved recovery of deep slips in both location and amplitude. When applied to the 2008 MW 7.9 Wenchuan earthquake, the method produced smaller slips near the ground surface and larger slips at depth. For the land-based deformation inversion of the 2011 MW 9.0 Tohoku earthquake, the method resulted in larger shallow slips near the trench and greater sea-floor uplift compared to the conventional inversion, which is valuable for accurate prediction of tsunami wave height. Additionally, this method may also be applicable to other inversions where smoothing is used and observation amplitudes vary with distance.