Synthetic Source Inversion Tests with the Damped Isochrone Inversion Approach

Abstract

Earthquake source parameters such as slip distribution and slip rate are useful information for understanding the physical processes behind earthquakes. The isochrone back-projection method, or isochrone-BPM, is one of the methods used to obtain slip distribution in the fault plane by incorporating the isochrone concept with back-projection method. Isochrone-BPM has advantages in its ease of implementation. However, it appears that the resulted slip distribution images always contain artifacts causing the images to be smeared. The emergence of these artifacts may lead to misinterpretation of the slip distribution, thus becoming a major weakness of isochrone-BPM. In this work, an alternative approach is proposed by utilizing least-square inversion scheme with the addition of damping factor as an alternative to the isochrone-BPM, which is then referred to as damped isochrone inversion since it still utilizes the core formulation of isochrone-BPM. The application of isochrone-BPM slip inversion to synthetic data generated from a test model shows that the quality of the resulted image will highly depend on the set of receiving stations used. In addition, the isochrone-BPM image will also depend on the focal mechanism of the earthquake, which is indicated by the difference in patterns on different mechanisms. Contrary to isochrone-BPM, the damped isochrone inversion produces slip distribution images that do not depend on the set of receiving stations used and do exhibit dependence on the focal mechanism. These results may suggest that as an alternative to the isochrone-BPM, the damped isochrone inversion offers better performance in recovering the slip distribution images.