Sensitivity Analysis of Soil Site Response Modelling in Seismic ... - ITC

3. Shake2000
3.1. Introduction
Local site effects influence the intensity of shaking, and they have been a popular research area for
many earthquake engineers, seismologists and other scientists. The reason is also it plays an important
role in earthquake resistant design of buildings. The basics of this analysis depend on the wave propagation
theory. In a nutshell the theory comes from seismology, which studies the ability of seismic
waves -vibrations of Rocks- to propagate through the Earth. Generally, seismic waves do not travel in
straight lines but are deflected, by refraction or reflection, by the layers they encounter, before they
return to the surface of the Earth and this allows the internal structure to be determined (Musset and
Khan 2000).
Using wave propagation theory combined with material properties and seismic input motion the expected
ground movement could be determined. This is done using quantitative inputs into complex
mathematical calculations. One of the earliest and most successful attempts was in the early seventies
when Schabel and Lysmer (1972) published, “A computer program for conducting equivalent linear
seismic response analyses for horizontally layered soil deposits” called SHAKE. This software was
based on Kanai (1951), Roesset and Whitman (1969), and Tsai and Housner (1970), SHAKE assumes
that the recurrent and circular soil behaviour can be simulated using an equivalent linear model (e.g.
(Kramer 1996)). From then, many upgrades and derived programs have been released. In general the
upgrades were focused on the user friendliness of the software; the fundamental part; the core algorithm
was left untouched. The program is still in use widely all over the world and the upgrades are
still continuing in the same way.
3.2. Background
The software that is used in this research is called SHAKE2000, which is a software package that integrates
ShakEdit and SHAKE. Computer programs such as WESHAKE (Wallace, 1999), ProShake
(Edu Pro Civil Systems, 2002) and ShakEdit are examples of the trend towards the development of
the next generation of user-friendly, geotechnical earthquake engineering software. ProShake, was
developed from EduShake, is a public domain program developed to help engineering students understand
the mechanics of seismic ground response. Differing from the ProShake, EduShake can only be
used with the seven ground motions that are included in the software itself. The development of
EduShake evolved through several stages and was eventually beta tested by graduate students, researchers
and practicing engineers. After a few modifications in response to the comments of beta testers,
EduShake was made public domain. Shortly thereafter, the restrictions of EduShake were removed
and a few additional features added to produce ProShake. And, ProShake featured a windows
graphical user interface that both simplifies and speeds the analysis and interpretation of seismic
ground response (Edu Pro Civil Systems, 2002 ).
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Sensitivity Analysis Of Soil Site Response Modelling In Seismic Microzonation For Lalitpur, Nepal