Potential applicability and limitations of radiation-corrected empirical Green's functions for point-source cases

Numerous efforts have been made to accurately estimate Green's functions, which link observed seismic waves to physical source processes. Detailed a priori information is required for the theoretical Green's function calculated from a given velocity structure. In contrast, the empirical Green's function (EGF) obtained from seismograms of nearby earthquakes with similar focal mechanisms requires the occurrence of such appropriate events. To partially release these constraints, we propose radiation-corrected EGF by correcting the radiation patterns of the EGF seismograms. In this study, we performed synthetic tests to quantify the applicability of radiation correction, together with its limitations. Such tests are a useful approach to test a benchmark of EGF applicability. We then applied the new method to real earthquakes to validate the concept for practical use. The synthetic test and real applications confirmed the superiority of the radiation-corrected EGF over the conventional EGF in specific, but realistic, cases.