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Resonance vs Shape of Sedimentary Basins

Description: 

The dynamic behaviour of sedimentary basins is traditionally studied in the frame of 1D plane-parallel conditions, when the aspect ratio of the basin is low, or by means of 3D numerical models, trying to replicate the real case. The latter, however, require not always available parameters and rely on not always verifiable assumptions. Between the idealized 1D and the real 3D cases, an intermediate 2D idealized case can be conceived, whose properties constitute an important link to overcome the limitations of the 1D approaches and towards the understanding of the complexity of real 3D cases. This intermediate case was studied in the '80s by means of analytical approaches and is here more systematically explored, by exploiting the power of numerical methods. Thus, we study the relations between the modal frequencies of idealized 2D sedimentary filled basins and their geometrical properties, under different Vs gradients, to show what information, often unused, might be hidden in the resonance frequencies of basins. We show that when a basin geometry is not known, but its modal frequencies have been experimentally assessed, the proposed relations offer a quick estimate of its aspect ratio, maximum depth, and equivalent shear-wave velocity of the sedimentary filling. When the basin geometry is known, the proposed relations offer a prediction of the expected modal sequence, thus helping in the design of future field surveys to better characterize the basin fill. The proposed relations help understanding the main parameters governing the modal sequence in a basin and to quantify the role and the weight of each parameter. This also provides constraints on the information and the degree of accuracy effectively needed in the input parameters of site response analysis. The conceptual elements will be presented in a historical perspective.

Session: How Well Can We Predict Broadband Site-Specific Ground Motion and Its Spatial Variability So Far? -III

Type: Oral

Date: 5/1/2024

Presentation Time: 02:15 PM (local time)

Presenting Author: Silvia

Student Presenter: No

Invited Presentation: 

Authors