A Frequency Domain based Inverse Ground Response Analysis Framework for the Determination of Dynamic Soil Properties

Abstract

Effect of local soil in amplifying bedrock motion during earthquakes (EQs) is an important phenomenon, and is observed globally. As a result, the bedrock motion at times increases manifold while reaching the surface. Such amplification in ground motions due to local soil is termed as local site effect (LSE), and can numerically be quantified by performing ground response analysis (GRA). Understanding the effect of local soil requires information about subsoil type as well as shear strain dependent behaviour of each subsoil layer (known as dynamic soil properties curves or DSPCs). Literature suggests that DSPCs of local soil are not readily available at regional level. Due to this reason, while attempting to estimate LSE, majority of site-specific studies consider DSPCs developed for other region's soils. DSPCs, though can be determined using existing inverse GRA methodologies, critical review done in this work highlighted that most of the frequency domain studies target to determine change in shear modulus (G) with shear strain (γ) but no to very limited studies target to determine damping ratio (β) variation with γ (or β curve). Additionally, these methodologies are limited to finding out soil properties for the surficial layer only. During an EQ excitation however, each of such soil layers will behave distinctively.