Free Software

FORTRAN or BASIC source code of seven computer programs mentioned in the text can be downloaded from the author's FTP site (see below). These are stand-alone programs for calibrating and testing seismometers and for standardizing noise specifications; they do not form a package for general seismic processing such as SAC, SEISMIC UNIX, PITSA, or PREPROC (see below). Whereever appropriate, the FTP subdirectory of each program contains test data, auxiliary files, and a Read.me file with detailed instructions. No graphics are included but some programs generate data files in ASCII format from which the signals can be plotted. The programs are:

• CALEX: Determines parameters of the transfer function of a seismometer from its response to an arbitrary input signal. Input and output signals must both be digitally recorded. The transfer function is implemented in the time domain as an impulse-invariant recursive filter. Parameters represent the corner periods and damping constants of subsystems of first and second order.
• DISPCAL: Determines the generator constant of a horizontal or vertical seismometer from an experiment where the seismometer is moved stepwise on the table of a machine tool or a mechanical balance.
• TILTCAL: Determines the generator constant of a horizontal seismometer from an experiment where the seismometer is stepwise tilted.
• SINFIT: fits sinewaves to a pair of sinusoidal signals and determines their frequency and the relative amplitude and phase.
• UNICROSP: Estimates seismic and instrumental noise separately from the coherency of the output signals of two seismometers.
• NOISECON: converts noise specifications into all kind of standard and nonstandard units and compares them to the USGS New Low Noise Model [Peterson 1993]. Interactive program available in BASIC, FORTRAN, C and as a Windows 95 - Executable.
• POL_ZERO: a BASIC program and Windows-95 executable for an interactive evaluation of the analog part of SEED data headers, producing a plot of the amplitude response versus frequency.

ftp server: ftp.geophys.uni-stuttgart.de (141.58.73.149)
name: ftp
password: your e-mail address
directory: /pub/ew
Author's address:
Erhard Wielandt
Institute of Geophysics
University of Stuttgart
Richard-Wagner-Str. 44
D - 70184 Stuttgart, Germany
e-mail: ew@geophys.uni-stuttgart.de

Free seismic software packages from other sources:

• SAC: http://www.llnl.gov/sac/SAC_Info_Install/Availability.html
• SEISMIC UNIX: http://www.cwp.mines.edu/cwpcodes/index.html
• PITSA: http://www.uni-potsdam.de/u/Geowissenschaft/Software/
  haupt_software.html
• PREPROC: ftp://orfeus.knmi.nl/pub/software/mirror/preproc/
  index.html

If you cannot find these websites, try

• http://www.seismolinks.com/Software/Seismological.htm
• http://orfeus.knmi.nl/other.services/software.links.shtml