Comparison of the Spectral Representation Method to Simulate Spatially Variable Ground Motions

The spectral representation method (SRM) is widely used when simulating spatially variable ground motions. It has mainly two formulas, i.e., the random amplitudes and the random phases formulas. There exist three methods for decomposing the cross spectral density matrix: Cholesky decomposition, eigen decomposition, and root decomposition. Therefore, there are six forms with respect to the different combinations of the simulation formulas and the decomposition methods. To provide researchers and engineers with the guidance on choosing simulation method, the six forms are systematically investigated from five aspects: the power intensity, response spectra, and stochastic error of auto/cross spectral density, Fourier spectra, and difference indexes for Fourier amplitudes and phases. Finally, we give the following advice: the characteristics of the ground motions simulated by the random amplitudes formula are independent of the decomposition method, while the characteristics of the ground motions simulated by random phases formula are dependent of the decomposition method. Furthermore, the root decomposition is strongly recommended when utilizing the random phases formula.     

Egyptian Scarabs Discovered on Kuwait’s Failaka Island and Similar Finds from the Gulf Region

Over the course of the last three decades, Ancient Egyptian scarabs have been discovered on Failaka Island off Kuwait, as well as at other sites in the Arabian Gulf. A scarab is the most expressive amulet of the cultural identity of ancient Egypt, revealing its influence and its cultural diffusion in the ancient world. Therefore, this paper discusses the reasons for the presence of such exotic products on the island and also answers the question about their origin. Were Failaka scarabs locally manufactured? What is their connection to the Levant? Are they a testimony to the interconnection between ancient Egypt and Arabia?