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Geophysical evaluation of the geotechnical properties of Quaternary sediments fron the continental margin, northwest of the UK

Finlayson, K.A. (1999) Geophysical evaluation of the geotechnical properties of Quaternary sediments fron the continental margin, northwest of the UK. PhD thesis, Prifysgol Bangor University.

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Abstract

There are a number of inherent problems associated with the interpretation of high resolution seismic data based on seismo-stratigraphic techniques. This is particularly true in complex, glacially influenced depositional environments, and groundtruth data are vital for calibrating the interpretation. Forward modelling, based on data from borehole logging, is one approach which can be used to predict and relate groundtruth data and seismic data in order to understand the seismic character and response. However, during engineering site investigations continuous geophysical logging is not routinely carried out and hence forward modelling is not easily undertaken. The aim of this project was to investigate inter-relationships between borehole sample derived properties ('Borehole method'), cone penetrometer test results ('CPT method') and the seismo-acoustic response. This investigation aimed to overcome the shortfall in continuous logging data and to understand glacially derived sediments in a seismic facies context. High resolution seismic data in digital form were analysed to calculate seismic attributes to test the relationships between physical properties and the seismo-acoustic response. The ultimate aim of the project was to test the applicability of an integrated approach to high resolution seismic data interpretation. The global empirical inter-relationship which was adopted in the study to predict acoustic properties for the 'Borehole method' was shown to be applicable for glacially influenced continental slope sediments, and the `Borehole method' reliably predicted the seismic response. However, it was noted that caution is needed to avoid aliasing as a function of geotechnical sampling frequency. The `CPT method' was able to produce predictions of major lithologic units through the blockaveraging method, and site specific empirical inter-relationships were derived to predict acoustic properties from the CPT results. The geophysical and geotechnical integration was shown to be very useful for determining the depositional environment and for calibrating seismic facies and character analysis. The seismic attribute analysis produced a reliable method of inferring physical properties based on amplitude variations. The results presented in this study have shown that by integrating methods of geotechnical and geophysical interpretation, modelling techniques can be successfully applied to improve calibration within the seismostratigraphic interpretation approach to high resolution seismic data.

Item Type: Thesis (PhD)
Subjects: Degree Thesis
Departments: College of Natural Sciences > School of Ocean Sciences
Degree Thesis
Date Deposited: 14 May 2015 05:18
Last Modified: 13 Apr 2016 15:41
URI: http://e.bangor.ac.uk/id/eprint/4499
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