Incorporation of Local Site Effects in Broadband Simulations of Ground Motions: Case Study of the Wildlife Liquefaction Array

Ramin Motamed, & John G. Anderson

Published October 20, 2016, SCEC Contribution #6804, 2016 SCEC Annual Meeting Poster #281 (PDF)

Poster Image: 
The principal objective of this research is to explore the most efficient approach to incorporate local site effects in Broadband (BB) simulations of ground motions and include the nonlinear soil behavior in the overall response. In this research, we will utilize ground motions recorded at the Wildlife Liquefaction Array (WLA) in Southern California for the purpose of validation of this research.

We will select at least 10 seismic events recorded by this array. The selected data will be grouped into two categories: (1) Category 1 which includes small-to-moderate ground shakings which initiated negligible excess pore water pressure and limited soil nonlinearity, and (2) Category 2 which consists of strong motions produced significant excess pore water pressure and substantial soil nonlinear behavior.

This study will explore different approaches in incorporating local site effects in the BB simulations including:
1. Direct method: in this method, the subsurface soil properties are explicitly incorporated in the BB simulations. An equivalent linear approach is possible in this alternative, at least with the Composite Source Model approach (Anderson, 2015) since this model retains a full wave propagation solution at high frequencies.
2. Two-stage simulation: consisting of the BB simulations for predicting motions for some horizon beneath the surface and then calculating the soil response using one of the Site Response Analysis (SRA) programs such as Deepsoil (Hashash et al. 2015) or D-MOD2000 (Matasovic and Ordonez 2011).
3. Transfer function method: because in many cases, less information is available than what is known of WLA, our experiences with the above approaches will be used to evaluate the use of transfer functions, including phase, that can be applied to surface synthetics.

We will evaluate the efficiency of different methods in inclusion of local site effects in the BB simulations using recorded data at WLA and quantify the quality of predictions using the Goodness-of-Fit (GOF) concept proposed by Anderson (2004).

Key Words
Local site effects, Broadband simulations, CSM

Motamed, R., & Anderson, J. G. (2016, 10). Incorporation of Local Site Effects in Broadband Simulations of Ground Motions: Case Study of the Wildlife Liquefaction Array. Poster Presentation at 2016 SCEC Annual Meeting.

Related Projects & Working Groups
Ground Motion Simulation Validation (GMSV)