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U.S. Geological Survey Open-File Report 77–671

A FORTRAN Program for Calculating Nonlinear Seismic Ground Response

By William B. Joyner

Thumbnail of and link to report PDF (31.3 MB)Introduction

The program described here was designed for calculating the nonlinear seismic response of a system of horizontal soil layers underlain by a semi-infinite elastic medium representing bedrock. Excitation is a vertically incident shear wave in the underlying medium. The nonlinear hysteretic behavior of the soil is represented by a model consisting of simple linear springs and Coulomb friction elements arranged as shown. A boundary condition is used which takes account of finite rigidity in the elastic substratum. The computations are performed by an explicit finite-difference scheme that proceeds step by step in space and time. A brief program description is provided here with instructions for preparing the input and a source listing. A more detailed discussion of the method is presented elsewhere as is the description of a different program employing implicit integration.

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Contact Information, Earthquake Science Center, Menlo Park Science Center
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345 Middlefield Road, MS 977
Menlo Park, California 94025

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Suggested citation:

Joyner, W.B., 1977, A FORTRAN program for calculating nonlinear seismic ground response: U.S. Geological Survey Open-File Report 77–671, 50 p., available at



Soil Layers

Input Motion

Resolution, Stability and Filtering

General Description of Output

Instructions for Preparing Input

Memory and Time Requirements

Variables in Printer Output not Previously Defined

Other Important Variables

Description of Subroutines

Sample Problem




Sample Problem Input Deck

Sample Problem Printer Output

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