Characterization of ground motion variability due to the presence of the built environment

Ricardo Taborda, & Yigit D. Isbiliroglu

Submitted June 25, 2018, SCEC Contribution #7993

Spatial variability and ground motion uncertainty during earthquakes can significantly influence both our interpretation of seismic data and the behavior of structures and infrastructure systems, especially those susceptible to differential motions, or those that benefit from more diffuse wave-fields. Spatial variations typically observed in ground motions are mostly the consequence of wave interferences, refraction, scattering and other phenomena resulting from the three-dimensional nature of the crust, the surface topography, site conditions, and heterogeneities in the transmitting media. Also influential but regularly ignored is the presence of the built environment, especially in the case of densely urbanized regions. In this study we investigate the extent to which the presence of building-foundation systems can modify earthquake ground motions and contribute to their variability. We perform a series of three-dimensional simulations using a finite element software for seismic wave propagation problems, with and without the presence of simplified building (block) models. We analyze the potential correlations that exist between wave-field perturbations (or relative changes in ground motion with respect to the free-field response) and the collective characteristics of building clusters (urban density, or inter-building spacing and total number of buildings per measure of area, and the individual structural dynamic properties of buildings). To this end, we identify parameters that can serve as proxies to characterize urban environments and measure the changes on the ground motion in terms of spatial distribution, amplitude, duration, and frequency content. We draw conclusions relevant to urban planning and seismic hazard analysis, and attempt to identify some of the observations from our models in strong motion data from monitoring stations located within dense urban areas.

Taborda, R., & Isbiliroglu, Y. D. (2018, 06). Characterization of ground motion variability due to the presence of the built environment. Poster Presentation at 11th National Conference in Earthquake Engineering.