MASTODON Theory Manual
MASTODON User Manual for Site-Response Analysis (coming soon)
MASTODON User Manual for Soil-Structure Interaction Analysis (coming soon)
Implementation of SSI capabilities in MOOSE: Mastodon
MOOSE is an open-source multi-physics simulation environment developed at INL. The Seismic Research Group is currently in the process of implementing seismic analysis capabilities in MOOSE, through the application called Mastodon. Once implemented, Mastodon will be capable of performing nonlinear three-dimensional seismic SSI analysis. Current capabilities are described below.
Earthquakes originate due to rupture of a fault segment. The P and S waves resulting from this rupture traverse the soil domain to reach the site location where the structure of interest is located. Mastadon has the capability to model a concentrated fault rupture (using a point source) or a fault segment rupture (using a combination of point sources). Non-reflecting boundary conditions (Lysmer dampers) have also been implemented in Mastadon to model infinite half-spaces. The animations below show a half-space with waves being generated by different kinds of sources.
a. Point source
b. Horizontal (left) and inclined (right) planar sources
Domain Reduction Method
Source to site simulations often require modeling kilometers of soil
domain and hence are computationally expensive.
Domain reduction method (DRM) is a two-step finite element methodology
used for modeling earthquake ground motion in localized heterogeneous regions.
In this first step of this method, the big soil domain with the earthquake source
but without localized features (like structure and other localized heterogeneity)
is modeled first. The second step solves a much smaller soil domain which
contains the localized features. The second step takes as input a set of
effective forces, which are calculated from the displacements obtained in the
first step. This methodology significantly reduces the computational effort.
Bielak, J., Loukakis, K., Hisada, Y. and Yoshimura, C. (2003), Domain Reduction Method for Three-Dimensional Earthquake
Modeling in Localized Regions, Part I: Theory, Bulletin of Seismological Society of America,