A database of revised fault plane solutions for Italy and surrounding regions

Abstract

The analysis of fault plane solutions of earthquakes is carried out in most seismotectonic studies to characterize the tectonic deformation styles and to estimate strain and stress directions in the investigated areas. Nevertheless the data available in the literature, are reported with different formats and notations and, in most cases, only in papery form, so that they are not suitable to be handled by computer procedures and graphic packages. Sometimes the data are reported with typographical errors, inaccuracies and inconsistencies that make them almost useless for other investigators. In some cases several solutions, often very different among each other, are given for the same earthquake by different authors thus requiring a choice be made among them. We have tried to solve some of these problems, in building a comprehensive database, on a Microsoft ACCESS platform, including most of the mechanisms (presently about 5000) published for the Italian region and more generally for the Mediterranean area. We tested the perpendicularity of nodal planes and/or P and T axes of all solutions and, when both axes and planes are given, even their mutual consistency. Moreover from the comparison of planes and axes we were able to detect and sometimes to correct misprints and other types of errors. All the parameters are recomputed uniformly and consistently, keeping track of all the corrections made. We also established an automatic procedure, based on several criteria, to choose the most “representative” solution when more than one is available for the same earthquake. The MS-ACCESS application also allows to making selections on the earthquake data, to display the plot of the mechanisms and to export data files suitable to be handled by graphic software and user written procedures.