Three-dimensional dynamic modelling of earthquake tremors

2000. Three-dimensional dynamic modelling of earthquake tremors / by N. Leenders, MS Thesis, Delft University of Technology, Delft (2000). ABSTRACT, supervisor(s): Hack & Scarpas (Technical University Delft), thesis availability: Technical University Delft

ABSTRACT

In this research a three-dimensional dynamic elasto-plastic finite element model is developed to simulate earthquake response for a three-dimensional irregular topography in the city of Armenia, Colombia.

Topographical and geomorphologic effects may be the cause for high local accelerations during the earthquake of January 1999. This effect has been studied for a simple geometrical model. In this study, the Brasilia Nueva area has been chosen as a test site for this purpose. The Brasilia Nueva area, situated on a narrow ridge, shows more damage than the surrounding area. Three-dimensional modeling is necessary because one- and two-dimensional simulations cannot model site effects, since these effects incorporate geometry and different waves traveling in three directions. The three-dimensional modeling of earthquake response has resulted in amplifications for different locations and directions in a small area (250m x 750m). Ratios of maximum acceleration at the surface, and the input signal, are displayed, irrespective of the frequency and dependent on the frequency. The selection of an appropriate constitutive model is very important. This model should correctly represent the main features of (dynamic) behavior while behaving mathematically accurate, using soil parameters that can easily be obtained in field and through laboratory tests. The parameters used for modeling are derived from investigations described in INGEOMINAS reports.

The results show that with finite element modeling it is possible to simulate strong ground motion for a small area. The actual damage pattern in the Brasilia Nueva area, caused by the January 1999 earthquake, does show great similarities with the results of the analysis. The presence of high accelerations in the Brasilia area, in the dangerous frequency ranges for local structures, has also been found in the model near the top and close to the edges.