Overview

Summary: Package for determining and displaying earthquake focal mechanisms.

Author: Arthur Snoke

Description: This package contains software for determining and displaying double-couple earthquake focal mechanisms. Input are polarities (P, SV , SH) and amplitude ratios (SV/P, SH/P, SV/SH). The main program, Focmec (coded in Fortran 77), performs an efficient, systematic search of the focal sphere and reports acceptable solutions based on selection criteria for the number of polarity errors and errors in amplitude ratios. The search of the focal sphere is uniform in angle, with selectable step size and bounds. The selection criteria for both polarities and angles allow adjustment through weightings for near-nodal solutions. Published applications include determinations of best-constrained fault-plane solutions for suites of earthquakes recorded at local to regional distances, analysis of large earthquakes observed at teleseismic distances, and the use of recorded polarities and relative
amplitudes to produce waveform synthetics.