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U.S. Geological Survey Open File Report 99–23, Version 1.1

HYPOELLIPSE: A Computer Program for Determining Local Earthquake Hypocentral Parameters, Magnitude, and First-Motion Pattern

By John C. Lahr

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This report provides Fortran source code and program manuals for HYPOELLIPSE, a computer program for determining hypocenters and magnitudes of near regional earthquakes and the ellipsoids that enclose the 68-percent confidence volumes of the computed hypocenters. HYPOELLIPSE was developed to meet the needs of U.S. Geological Survey (USGS) scientists studying crustal and sub-crustal earthquakes recorded by a sparse regional seismograph network. The program was extended to locate hypocenters of volcanic earthquakes recorded by seismographs distributed on and around the volcanic edifice, at elevations above and below the hypocenter. HYPOELLIPSE was used to locate events recorded by the USGS southern Alaska seismograph network from October 1971 to the early 1990s. Both UNIX and PC/DOS versions of the source code of the program are provided along with sample runs.

Last modified April 25, 2012
First posted February 1999

  • This report is available only on the Web.

For additional information:
Contact Information, Earthquake Science Center, Menlo Park Science Center
U.S. Geological Survey
345 Middlefield Road, MS 977
Menlo Park, California 94025

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Suggested citation:

Lahr, J.C., 1999, revised 2012, HYPOELLIPSE: a computer program for determining local earthquake hypocentral parameters, magnitude, and first-motion pattern: U.S. Geological Survey Open-File Report 99–23, version 1.1, 119 p. and software, available at


Chapter 1 - Introduction to HYPOELLIPSE

Chapter 2 - HYPOELLIPSE Users Guide

Chapter 3 - Error Estimates

Chapter 4 - Magnitude Determinations

Chapter 5 - Determination of Vp/Vs Ratio

Chapter 6 - Generating Travel-Time Tables

Chapter 7 - Use of Cylindrical Delay Regions

Chapter 8 - Summary of Important Formats

Chapter 9 - Acknowledgements

Chapter 10 - References


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