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Title: Propagation and dissipation of VHF Rayleigh waves in Scotland
Author: Evans, Andrew C.
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1982
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This work is an analysis of Rayleigh waves with frequencies of around 1 to 3 Hz, observed from four explosions fired in Scotland during the large scale refraction project LISPB. Time domain measurements are made from reduced tra.vel time sections showing recordings from the linear LISPB array in northern Scotland and for isolated paths around the LOWNET network in the Midland Valley and to the EKA array in the Southern Uplands. These show a division of the country into seven separate provinces with boundaries marked by sharp velocity changes and sudden attenuation, co-incident with features of the mapped surface geology. In the frequency domain, group and phase arrival times and amplitude are obtained for each Rayleigh wave recorded. After least squares analysis, phase and group slowness (s (f), s (f)) are c u obtained for each of the seven provinces and the specific dissipation factor (Q~1(f)) for five. s (f) ranges from 0.329 to 0.610 s/km and generally increases c with frequency, consistent with s (f) which is always larger. u ranges from 0.015 to 0.050. These data are inverted using both linear and Hedgehog methods to obtain shear wave velocity (~) and the shear wave dissipation factor (Qp1) in layered models for the upper 2 km of the crust in each province. generally increases with depth, due to compaction and near surface weathering. It also increases with geological age, which ranges from the Carboniferous of the Midland Valley to the Moine of northern Scotland. A low velocity zone beneath the Ochil Hills indicates that Devonian lavas overlie Old Red Sandstone whichoutcrops further north. Q~ generally increases with depth also. Introducing a Q~1(f) which varies as f-O.5 makes no marked change to the models, with a tendency for larger values at shallow depth and smaller values deeper down
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Communication systems & telecommunications Communication