Normal mode detection and splitting after Sumatra–Andaman earthquake

Apart from life loss and damages which earthquakes cause, their signature in the collected data either seismic and/or gravity enables us to define their location and dislocation (i.e., geometric parameters), time of occurrence, and magnitude. In addition, the Earth’s interior physical parameters, such as density profile and anelasticity can be defined. Gravity data contribute additional knowledge about the Earth’s interior through careful analyses of superconducting gravimeter (SG) records particularly after strong earthquakes. In this paper, SG data recorded after the Sumatra–Andaman earthquake in December 26, 2004 at eight SG stations, are used to investigate the properties of the long-period seismic modes: their frequencies, amplitudes, and quality factors. These parameters are estimated very precisely in this study for the spheroidal modes S00, S02 and S03. In addition, for the first time we observe the toroidal modes T14 and T15.