FPFIT, FPPLOT and FPPAGE; Fortran computer programs for calculating and displaying earthquake fault-plane solutions

Abstract

inability of FPFIT to perform its uncertainty analysis without a full range of solutions neighboring the adopted solution.Hence, the restricted search mode should only be used in special studies in which a "forced" solution is desired and estimates of solution uncertainty are not needed.The unrestricted search mode is invoked by including in the input control file only lines 1, 2 and3, and(optionally) station status lines, as in Appendix examples B.I,a and B.l.b (see also Section V.B).The restricted search mode is invoked by including in the input control file an additional line specifying the ranges of the restricted search, as in Appendix examples B.l.c and B.l.d.V. Input Files A. Data File: FPFIT reads the print output file from program HYP071 (Lee and Lahr, 1975).This file contains the hypocenter summary card, followed by (for each P-wave observation) the station-to-epicenter distance and azimuth, P-remark, angle of incidence, and flag denoting phase data discarded due to Jeffrey's weighting.B. Control File (see appendix B.I): This file sets parameter values to tailor the computation to suit the particular requirements of the data set.At least three lines are required: Line 1 -DISTMX, FMAGMN, MINOBS, IPRNT, IJEFF, NEV, DFITC (free format) Name Explanation DISTMX Maximum epicentral distance in km.Phase data from stations at epicentral distances greater than DISTMX are ignored.I FMAGMN Minimum magnitude.Fault-plane solutions are not computed for events with magnitudes smaller than FMAGMN.MINOBS Minimum number of observations.Fault plane solutions are not computed for events f<j>r which NOBS < MINOBS.IPRNT Print output control.If IPRNT = 1, FPFIT generates a listing of the misfit function for each test solution in the fine search.Normally, I^RNT = 0. IJEFF Jeffrey's weighting control.When I JEFF = 1, inversion includes phase data discarded!byJeffrey's weighting in HYP071.When IJEFF = 0, phas|» data discarded by Jeffrey's-weighting are omitttd NEV Maximum number of events for ^hich fault plane solutions will be calculated.Solution^ are calculated sequentially i from the input file until NEV events have been processed.DFITC Depth of search for relative minima in misfit.Relative minima with F < F .+ DFITC are considered.We mm recommend the value DFITC=0.05 be used for most applications.Line 2 -ERATE(l), ERATE(2), ERATE(3), ERATE(4) (free format) Name Explanation ERATE Estimated weighted error (discrepancy) rates for classes of hand-picked data.ERATE(J+1) corresponds to assigned pick quality J. Set ERATE(J+1) = class J.For 0.0 < ERATE(J) better-quality data.Use actual weighted error rates reported in a previous run of FPFIT on same data for best estimates of ERATE.1.0 to exclude all data from < 0.5 lower values reflect with an asterisk (*) to indicate multiple solutions.Compressions!rays are depicted as solid circles; dilational rays as opein circles.Plotting of the first motion symbols may be suppressed by the user.Finally the P-and T-axes of the solution are plotted.If first-motion plotting is suppressed, only the T-axis is plotted.