Empirical Green's functions calculated from the inversion of earthquake radiation patterns

Abstract

In this paper, the empirical Green's function is calculated based on a method that inverts the radiation patterns of earthquakes. The method utilizes several close-lying earthquakes with known focal mechanisms that are received by a common seismic station. The empirical Green's function between the given source area and the seismic station is then calculated by extracting common features and phases from earthquake waveforms. This is achieved through removing the effect of focal mechanisms from the waveforms and combining the remaining terms based on a damped least-squares approach. The resulting function represents the main characteristics of the propagation path after the waves have left the source area until they are received by a given seismic station. The application of the method is not limited by any requirement to make any separations of seismic phases and the earthquakes used are not required to have the same focal mechanisms. In this research the method is applied to two different data sets, including local Icelandic and regional Iranian earthquakes. In the latter data set the 1990 June 20 Iranian earthquake (Mw = 7.4) was modelled at broad-band seismic station KIV in Russia.