Study of directionality in ground motions recorded on soft soils
Journal
World Conference on Earthquake Engineering proceedings
ISSN
30065933
Publisher
International Association for Earthquake Engineering
Date Issued
2024
Type
text::journal::journal article
Abstract
Directionality of ground motions refers to changes in ground motion intensity with changes in orientation. Previous studies have investigated the directionality of response spectral ordinates of ground motions recorded on rock or firm soils. However, there are no studies on the directionality of ground motions recorded on very soft soil deposits. The present study focuses on quantifying the directionality of horizontal components from strong motions recorded in stations located on the soft soils of Mexico City, and develops models for estimating the maximum horizontal component (RotD100), the recently proposed median of the maximum of two orthogonal components (MaxRotD50), and their corresponding variabilities as a function of periods of vibration normalized by the fundamental period of the site and the median spectral ordinate for all non-redundant orientations ordinate (RotD50). These models are developed after analyzing the results from 625 record pairs obtained during 26 major earthquake events in Mexico. These events have moment magnitudes between 6 and 8.2 and were recorded at stations with fundamental periods of vibration between 1 and 3s. Results demonstrate that horizontal components show larger directionality as the period of vibration increases, similar to what has been observed in stiff soils, but an additional increase in directionality in spectral ordinates is observed for periods of vibration equal to or close to the predominant period of the site. More specifically, it is observed that RotD100 and MaxRotD50 values are 25% and 18% larger than the RotD50 component, respectively, when the period of vibration coincides (i.e., is tuned) with the period of the site.
License
Acceso Restringido.
URL License