Instructions for Getting Surface-Wave Velocity Spectra
from Data Recorded on Seismic Refraction Equipment

John Louie, 18 May 1999
Copyright © 1999 John N. Louie, all rights reserved.

Purpose

Surface-wave velocity spectra can determine shallow earth structure and contribute to the estimation of earthquake ground-shaking hazards. This tutorial details how to analyze surface-wave data recorded on common seismic refraction equipment. The surface waves can arise from controlled sources, or from microtremor noise. It does not describe how to record surface waves in the field, much about how to derive a velocity structure from a dispersion curve, or how to interpret S-wave velocity structure for any particular purpose. This turorial is meant to function as an aid to laboratory exercises in undergraduate geophysics university courses.

More information on the use of refraction equipment to estimate S-wave velocity structure is available in the following draft reports:

George A. McMechan and Mathew J. Yedlin, then of Stanford University, originally published the slantstack and Fourier transformation analysis method used here in 1981, as ``Analysis of dispersive waves by wave field transformation,'' in volume 46 of Geophysics, on pages 869-874.

Detailed Instructions

There are several steps involved in getting data from the seismograph to a computer where you can do the surface-wave analysis. These steps are broken down according to the kind of computer needed. While the main analysis you can do on almost any computer, you may need a certain type of system for other steps. For those steps, I provide here software for Sun computers with SPARC processors and the Solaris 2 operating system only. Your department may already have its own means for these steps.

The software and methods here are the subject of academic research, not commercial products. I would like to know what use you make of my methods, and have your feedback on their success or failure. Also, by letting me know who you are, I can inform you if bugs or errors are discovered.

Please send me an email message with: your name and email address; whether you are a student or faculty member, consultant or employee; the name of your university or company, and department; and a sentence or two describing what use you intend to make of these methods. Send your message to louie@seismo.unr.edu

  1. Convert the data from the seismograph (Sun only)

  2. Obtain the Java software (any computer)

  3. Run the velocity-spectrum analysis (any computer)

  4. Model structure from the results (Sun only)