ROLE OF A-PRIORI INFORMATION IN MINIMIZING UNCERTAINTIES IN MASW TESTING AND SUBSEQUENT SITE RESPONSE ANALYSIS

Abstract

Earthquakes cause heavy destruction to human lives and the economy. Especially, when there are deficiencies in preparedness against earthquakes, the damage becomes enormous. The recent 2023 Turkey earthquake aptly demonstrated that the flaws in earthquake-resistant design lead to unbearable consequences. A pivotal exercise for any earthquake-resistant design is the estimation of the shear wave velocity (Vs) profile of the soil. However, the most commonly used method for that, the multichannel analysis of surface waves (MASW), is fraught with several uncertainties. Even more concerning is the fact that the practitioners often carry out the MASW test without using apriori information. A literature review on surface wave methods revealed that only 5% of the articles on MASW testing explored joint/constrained inversion during Vs profile estimation, despite the availability of a-priori information (Socco et al., 2010). Neglecting the consideration of a-priori information may lead to gross errors in earthquake-resistant design, with potentially deadly consequences during an earthquake. Therefore, understanding the role of a-priori information in Vs profile estimation during MASW testing is of utmost importance. The objective of this thesis is to investigate the influence of a-priori information on the three types of uncertainties associated with MASW testing, namely inversion uncertainty, data measurement uncertainty, and model-based uncertainty. The primary aim is to quantify the extent of uncertainty that arises in the absence of a-priori information and determine the degree of uncertainty reduction achieved by incorporating a-priori information. The a-priori information is considered in the form of the number and thickness of soil layers and the index properties of soil, which are available from the commonly carried out geotechnical field investigations.