13 th National Congress on Civil Engineering 10 & 11, May 2022 Isfahan University of Technology, Isfahan, Iran 1 On Seismic Response of Attenuated Orthotropic Gaussian- Shaped Sedimentary Basin Saeed Mojtabazadeh-Hasanlouei 1 , Mehdi Panji 2* , Mohsen Kamalian 3 1, 2- Department of Civil Engineering, Zanjan Branch, Islamic Azad University, Zanjan, Iran. 3- Geotechnical Engineering Research Center, International Institute of Earthquake Engineering & Seismology, Tehran, Iran. mojtabazadeh@iauz.ac.ir m.panji@iauz.ac.ir kamalian@iiees.ac.ir Abstract The surface motion of an orthotropic Gaussian-shaped sedimentary basin embedded in a linear elastic half- space was successfully obtained under transient SH-wave propagation. In the use of the time-domain boundary element approach, a simple model was developed only by discretizing the interface. To achieve better convergence of the response, an attenuation rule was implemented with the assistance of the reduction exponential function applied in the boundary integral equations. After a brief overview of the method, the heterogonous sub-structured basin model was created and decomposed into two parts to satisfy the modified continuity conditions based on the normal direction at the interface node position. The developed computer code was tested by solving a validation example. Finally, to illustrate the basin surface response in the time/frequency-domain, a general sensitivity analysis was performed by considering the parameters of frequency, isotropy-factor, wave angle, seismograms, and amplification patterns. The results showed that the effect of orthotropic anisotropy was very efficient on the ground response and different seismic patterns on the surface of sedimentary basins were extracted by changes in the quantity of this parameter. Keywords: Orthotropic half-space, Sedimentary Basin, Seismic anisotropy, SH-wave, Time-domain BEM. 1. OVERVIEW Sedimentary basins are among the most important topographic features in geotechnical/earthquake engineering; because many cities are located on them. Therefore, it is necessary to study their seismic behavior using modern methods to eliminate its unknown aspects more than before. In The boundary method which is known as Boundary Element Method (BEM), the high accuracy of the responses and the ease of modeling process cover the weaknesses of volumetric methods. By satisfaction of the wave radiation conditions in the infinite, this approach can significantly reduce the computational volume, the occupied memory, and the analysis time. Therefore, it can be one of the most ideal methods to analyze the infinite and semi-infinite models including the waves propagation in the topographic features. A review of the development history of isotropic BEM shows that Sánchez-Sesma & Rosenblueth (1979) were the pioneering researchers who conducted the first study on the ground motions in the presence of arbitrarily shaped canyons subjected to incident SH-waves using half-plane frequency-domain BEM. Then, Luco et al. (1990) illustrated the 3D responses of a cylindrical canyon in a layered half-space. Reinoso et al. (1993) presented the responses of the Mexico City valley. The seismic responses of semi-elliptical alluvial valleys due to incident SH, P, and SV-waves were presented by Fishman & Ahmad (1995). The seismic responses of alluvial valleys for incidence SH-waves were presented by Ausilio et al. (2008). Also, among the recent isotropic studies can refer to the works of Liu et al. (2019), Ba et al. (2020), Panji et al. (2021), Panji & Mojtabazadeh-Hasanlouei (2021), and Mojtabazadeh-Hasanlouei et al. (2020). The studies about the anisotropic bodies show that Maznev & Every (1997), Saez & Dominguez (2000), Watanabe & Payton (2001), Manolis et al. (2007), Daros (2013), and recently, Chiang (2018) were among the researchers who concentrated their works to obtaining elastodynamic Green’s functions, elastic solutions, the waves propagation and other aspects of anisotropy as well as orthotropy effects in engineering problems. The application of full-space BEM for wave propagation problems of the anisotropic, transversely isotropic, and orthotropic medium can refer to the studies of Wang et al. (1996), Zhang (2002), Chuhan et al.