STRENGTH AND ENERGY DEMANDS FROM THE AUGUST 1999 KOCAELI EARTHQUAKE GROUND MOTIONS

摘要

Traditionally, the intensity of ground shaking and the demand on structures has been characterized using parameters such as peak ground acceleration as well as strength-based parameters such as response spectrum ordinates (e.g., spectral acceleration) that represent the maximum amplitude of shaking for structures with specified natural periods and damping ratios. It has long been recognized that to understand the demands placed on structures during earthquakes one might also employ an energy-based approach, especially when there is an interest in assessing the damage potential of ground motions. An input energy spectrum, obtained with the same level of effort as is required to construct a conventional response spectrum, is a convenient single-parameter description of both amplitude and duration of ground motion and can be a useful means by which to describe the performance of structures. Both elastic and inelastic input energy spectra can be easily constructed - the latter can provide useful information for systems that undergo inelastic deformations (or that are designed with adequate ductility capacity) and for assessing the damage potential of ground motions. The two earthquakes that occurred in Turkey in 1999 and the damage suffered by structures in those events motivated the present study that examines recorded ground motions from those events. Input energy spectra and response spectra are computed for recorded ground motions from the Kocaeli earthquake. Several Western United States attenuation models have been established from a larger database of ground motions than are available for Turkey. Because of reported similarities between the San Andreas and the North Anatolian fault systems, strength and energy spectra estimated from Kocaeli motions are compared with these empirical attenuation models developed for the Western United States.