Urban seismology: Interaction between earthquake ground motion and response of urban regions

The objective of this research is to develop a numerical methodology, based on the Finite Element Method (FEM), capable of simulating three dimensional (3-D) ground motion during strong earthquakes, with the presence of buildings and urban environments as factors that can affect the nature of the same ground motion. There are four essential steps involved: (1) use of an integrated 3-D FEM code for modeling elastic wave propagation on parallel computers, such as Archimedes (Bao, et al. 1998); the code includes absorbing boundaries to minimize the occurrence of spurious wave reflections at the boundaries of the computational domain, and effective forces for representing the seismic excitation, both for incident waves arriving from outside the domain and for point or extended fault sources generated within the domain; (2) implementation and use of the Domain Reduction Method (DRM) for 3-D spaces (Bielak, et al. 2003), a very convenient methodology for the incorporation of equivalent forces that can match the effects of far field seismic excitations; (3) incorporation of Building Idealized Models (BIMs) into the original soil FEM mesh; the BIMs are mathematical representations of real buildings, based on FEM beam elements, which are capable of interacting with the existing soil mesh; and (4) comparison of free field motion to that resulting from the analysis that accounts for the interaction between the soil and the structures.; The work analyzes global effects as well as some local Soil Structure Interaction (SS1) phenomena. The models used correspond to idealized scenarios that resemble the geologic setting of the Mexico City Basin and the effects of a far field seismic event, such as the one that occurred in September of 1985.