Surface wave tomography in engineering: Move over MASW, FTAN is here.

Title: Surface wave tomography in engineering: Move over MASW, FTAN is here.

Presenter: Dr Craig O’Neil

Date: Wednesday 16th March 2022

Time: 6:00 pm to 7:00 pm AEDT

Registration: https://us02web.zoom.us/webinar/register/WN_cAHHIn2YQDe9VOWKmH-T6Q

Abstract:

Many large scale civil works, such as dams and foundations, require a detailed knowledge of the shear-wave velocity and elastic properties of the underlying bedrock. These properties determine the earthquake risk and ground acceleration of a dam, or the vibrational response of built structures. Over recent years, multichannel analysis of seismic waves (MASW) has been widely adopted to provide this information, and has been incorporated into engineering guidelines such as ANCOLD.  However, these methods are time intensive, and a high level of interpreter skill is needed to identify phase velocity modes within noisy data, and misinterpretation of fundamental modes can lead to unrealistic geological models.  Here we develop an approach from the research seismology realm - frequency time analysis (FTAN) - to provide an alternative approach. Field acquisition can co-opt existing refraction surveys, and uses a Gaussian-band filtering to identify fundamental and higher group velocity modes in the data, which can be inverted for vertical S-wave velocity structure. I show a number of field examples, and highlight the approache's ability to discern site-specific engineering information such as rock-mass classification, degree of weathering, and earthquake risk to structures. An explosion of development in renewable infrastructure, from wind onshore and offshore wind turbines and foundation characterisation, pumped hydroelectricity schemes, and geothermal reservoir development, is being seen recently, and the FTAN approach offers a reliable and affordable way of characterising local geotechnical properties

Bio:

Dr Craig O’Neill has over 17 years’ experience in geophysics, engineering geology, and computational geoscience. He has utilised geophysical techniques and geological approaches to deliver on diverse projects from groundwater exploration in remote communities, archaeological excavations in Italy, electromagnetics for copper mineralisation, and geothermal characterisation of deep sedimentary basins. He has supervised projects in slope stability and landslide risk in developing countries, drone photogrammetry, and rock mechanics. He developed a geotechnical laboratory and teaching program at Macquarie University, where he was also director of a major Research Centre. He also has a long experience with computational geoscience and machine learning. He has over 74 highly cited Earth Science papers, and was a member of the Australian Academy of Science’s National Committee for Earth Science, where he helped draft the National Decadal Plan