Nonlinear dynamic behavior of the basins with 2D bedrock

Due to copyright restrictions, the access to the full text of this article is only available via subscription.Resonance due to impedance contrast, focusing due to subsurface topography, conversion of the body waves to surface waves and subsurface topography are among the factors influencing the amplification specification of the sites, which can only be considered by the application of suitable nonlinear analysis method. In this study, using the fully nonlinear analysis method, along with a hysteretic-type model and no extra damping, the effects of the basin edge on the dynamic behavior of the basins is investigated in more accurate manner. To make the results useful at engineering affaires, the investigated basins are classified into sandy, clayey and layered basins. Special degradation curves for each of the (soft, medium plasticity and stiff) clay and (loose, medium dense and dense) sand types have been extracted and fitted to the continuous functions which is used by the nonlinear method's hysteretic-type damping scheme. The results exhibit the differences in the amplification behavior of the basins with different soil types under the different excitation levels. Also, the sensitivity of the different parts of the basin surface with 2D geometry to different period levels is investigated. This finding can be used at dynamic structural design of the buildings on basins with 2D bedrock inclination

2D non-linear seismic response of the Dinar basin,TURKEY

Due to copyright restrictions, the access to the full text of this article is only available via subscription.Local geological conditions generate significant amplification of ground motion and concentrated damage during earthquakes. The highly concentrated damages at the edges of the Dinar basin during occurred earthquakes at regions close to rock outcrop bring up the effect of the inclined bedrock effect on the dynamic behavior of the basin with 2D geometry. In this study, first the idealized 2D model of the basin based on the results of the underground explorations and geologic investigations is proposed. Results show that Dinar basin has an asymmetric 2D geometry with two different bedrock angles at edges. Then, a numerical study using finite difference based nonlinear code which utilizes appropriate static and dynamic boundary conditions, and includes hysteresis damping formulation based on the user defined degradation curves is conducted using real earthquake motions of different strength and frequency content. The constructed model is subjected to the collection of 16 earthquakes with different PGA's of 0.1, 0.2, 0.3 and 0.4 g, four motions for each PGA. It was seen that the dynamic behavior of the basin is broadly affected by the two dimensional bedrock. The results indicates the higher effect of the 6° bedrock inclination at east part on the amplification with respect to the steeper 20° bedrock slope at the west. Also, the results show the insignificant effect of the bedrock at the depth more than 150 m on the amplification of the east edge. While the effect of the 6° bedrock angle at the east part continues until 1500 m from the outcrop, it affects the amplification until 700 m from the outcrop at the west part with 20° bedrock angle

Interaction of geometry and mechanical property of trapezoidal sedimentary basins with incident SH waves

This paper investigated the effects of basin geometry and material property on the response of 2D trapezoidal sediment-filled basin to incident plane SH waves. Ten basin configurations with different geometries were developed, and then their seismic responses to both Ricker wavelets and seismic records were simulated by using an explicit finite difference scheme. The definition of deep/shallow basin, the precondition for the observation of prominent surface waves and the influential area of edge effects of the shallow basin were discussed quantitatively in this study. The followings were concluded: in the common velocity contrast range (v s1/v s2 < 10), the fundamental frequency a basin with W/H > 3.0 can be estimated approximately by 1D theory. The complexity of peak ground acceleration distribution pattern, the width of the most affected section as well as the amplitude of ground motion in the Edge Region increase with incident frequency. Prominent surface waves can only be observed when the incident wavelength is shorter than the critical wavelength λ c . The interaction between incident wave and basin dynamic property plays a dominant role on the peak ground acceleration amplitude while the interaction between incident wave and geometry plays a more significant role on the peak ground acceleration distribution. For very shallow basin, different areas along the basin width are affected to different extents. Only a limited area close to the basin edge is influenced significantly. It is more feasible to propose spectral aggravation factor for different surface zones respectively than a uniform constant as a tool to calibrate the 1D-based design spectrum so as to take the basin effects into account