Earthquake source is underground rupture. We can investigate the process of this underground rupture phenomenon, i.e., what happens at the earthquake source, from the analysis of the ground surface shaking data (seismic waveform data). "Approach to the mystery of earthquake rupture process using seismic waveform data" is the main research interest of mine.
In order to investigate what happens at the underground earthquake source using the ground surface shaking, we need knowledge on the mechanism of wave generation and propagation when rupture happens beneath the ground. This is provided by the physics called "Theory of Elastic Waves." The physics called "Theory of Rupture Dynamics" helps to understand the rupture phenomenon itself. For the data analysis, mathematical methods such as least square method are necessary. Knowledge of Linear Algebra helps it. Like this, physics and mathematics are powerful tools for the study on earthquakes. This was unexpected, and at the same time a pleasant surprise for me when I was a undergraduate student. This odd (?) combination of earthquakes, physics, and mathematics remains to give academic stimulation to me even after I became a professional researcher.
Kasatani, N. and Y. Kakehi (2014), Source effects of the intraslab and interplate earthquakes off Miyagi Prefecture in Northeastern Japan based on spectral inversion, Zisin, 67, 57-79, DOI:10.4294/zisin.67.57.
Kubo, H. and Y. Kakehi (2013), Source process of the 2011 Tohoku earthquake estimated from the joint Inversion of teleseismic body Waves and geodetic data including seafloor observation data: source model with enhanced reliability by using objectively determined inversion settings, Bull. Seismol. Soc. Am., 103, 1195-1220, doi:10.1785/0120120113.
Kakehi, Y. (2010), Structure of northeastern Japan arc and strong ground motions: strong ground motions from an intraslab earthquake and interplate earthquakes east off Fukushima prefecture, Proc. 13th JEES, 73, 3850-3857.
Kakehi, Y., Y. Saijo, and K. Somei (2010), Analyses of strong ground motions from intraslab earthquakes using high-density observation network data: relation to the island arc structure, Geophys. Bull. Hokkaido Univ.,, 73, 57-70.
Kimura, T. and Y. Kakehi (2005), Source process of the 2001 Hyogo-ken Hokubu, Japan, earthquake (Mw 5.2) and comparison between the aftershock activity and the static stress change, Bull. Seismol. Soc. Am., 95, 145-158.
Kakehi, Y., (2004), Analysis of the 2001 Geiyo, Japan, earthquake using high-density strong ground motion data: Detailed rupture process of a slab earthquake in a medium with a large velocity contrast, J. Geophys. Res., 109, B08306, doi:10.1029/2004JB002980.