Seismic Moment Tensor Solutions for Geophysical Mapping of the Philippine Sea Basin by GMT

This paper presents a GMT scripting technique for mapping seismic moment tensor solutions. The underlying geophysical properties and settings of the Philippine Sea Plate (PSP) situated on the margins of the Pacific Ocean are analysed. Active volcanism and high seismicity of this region located along the margins of the Philippine Sea Basin (PSB) results in a series of earthquake events caused by geodynamic processes of tectonic plate subduction. The proposed console-based framework of cartographic workflow is designed to perform mapping of the earthquake events using Generic Mapping Tools (GMT) modules, to analyse seismic setting through visualisation of the geophysical dataset. The materials include General Bathymetric Chart of the Oceans (GEBCO), Centroid Moment Tensor (CMT) and International Seismological Centre (ISC) seismic data. Technically, the algorithm of mapping by GMT consists in a consecutive use of modules used in a script run from a command line: 'psmeca', 'psvelo', 'img2grd', 'grdtrack', 'grdimage'. The GMT functionality is illustrated by the key snippets of code. The path to the full codes is provided with a link to the author's GitHub repository for technical repeatability. Furthermore, the algorithm of GMT enabled to visualise CMT solutions for shallow depth earthquakes of Mw < 10 along the PSB margins from 1976 to 2010. Thus, the paper also demonstrated and presented the performance of the GMT on a geophysical dataset that features complete earthquakes data along the zone of tectonic plate subduction from the Global CMT Project. In both technical and geophysical cases, this approach of GMT-based mapping presents cartographic workflow better than state-of-the-art traditional GIS programs through increased automation of the cartographic workflow. The study contributed to the development of methods of geophysical and seismic mapping using GMT scripting toolset by visualising focal mechanisms and seismic moment tensor solutions