Determination and Identification of Focal Mechanism Solutions for the 2016 Kumamoto Earthquake from Waveform Inversion Using ISOLA Software

Abstract

On April 14, 2016, at 21:26 (JST), a shallow earthquake of magnitude MJMA 6.5 occurred at Kumamoto prefecture in Kyushu region, Japan. It was one of the foreshocks before the main shock of magnitude MJMA 7.3 28 hours later, on April 16 hits the area. They began at the Hinagu fault zone, which intersects the main shock Futagawa fault zone, creating a complex tectonic context for this earthquake sequence. Here we find out the focal mechanism solution for the MJMA 6.5 earthquake. A software package ISOLA-GUI, a user-friendly MATLAB-based interface, developed by J. Zahradnik and E. Sokos, is used to find moment tensor solutions. It uses data from the three-component seismogram from a single station. The earthquake data is taken from strong motion records of the KiK-net networks. Full-wave seismogram data are used for inversion for single or multiple-point source earthquake models. This software is useful to find the moment tensor solutions where data at all azimuths are not available. The software uses a graphical interface that helps the user easily interact with the software and makes it easier to work. The software allows the result to be mapped using GMT. The focal mechanism solution from multi-station data has been shown along with a cross-plot of source depth and correlation. The power and SNR spectrum are also shown to assess the quality of the data. © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG 2024.