Surface Wave Dispresion between North and East Africa
| dc.contributor.advisor | Asfaw, Laike Mariam (PhD) | |
| dc.contributor.author | kebede, Fekadu | |
| dc.date.accessioned | 2018-06-22T09:23:44Z | |
| dc.date.accessioned | 2023-11-09T11:23:29Z | |
| dc.date.available | 2018-06-22T09:23:44Z | |
| dc.date.available | 2023-11-09T11:23:29Z | |
| dc.date.issued | 1983-06 | |
| dc.description.abstract | A comprehensive study of dispersion of surface Rayleigh waves for three paths: Gulf of Aden - Addis Ababa (GOA - AAE), Red Sea Addis Ababa (RES - AAE) and Arab republic of Egypt - Addis Ababa (ARE - AAE), lying between north and east Africa is made. Earlier studies of surface wave dispersion in the region were made for short epicentral distances without considering contribution by different modes. The problem of contribution by different modes to dispersion is inherent at short epicentral distance ranges. Rayleigh wave trains identified from seismograms of Addis Ababa seismic station (AAE) are enlarged and digitized. The results are analysed using fixed window Fourier analysis and moving window analysis (Landisman et a1. 1969). These methods have advantages in displaying different modes which otherwise would be absent if the usual peak and trough method is used. Dispersion curves obtained by the above methods and the usual peak and trough method are compared with theoretical dispersion curves generated for different crustal models. An efficient algorithm developed for solving the period equation on a computer (Dunkin 1965; Robert H. Herrman personal communication 1980 ) is used to obtain theoretical dispersion curves up to ten modes. However, in this study the fundamental and first modes were found adequate to explain the seismogram observations. A total of 150 theoretical models each with multimode outputs were considered. A crustal thickness of 27 km with high Poisson's ratio overlying an anomalous mantle (,d-- = 7.2 km/sec) 4 km thick is found for GOA - AAE path. For RES - AAE and ARE - AAE paths crustal thicknesses of 37 km and 38 km respectively overlying a normal mantle are found. The Poisson's ratios for these paths are similar to that of a 'normal continental crust. Regarding resolution of modes for the period range considered in this study both moving and fixed window methods give similar results indicating that the former method is superfluous | en_US |
| dc.identifier.uri | http://10.90.10.223:4000/handle/123456789/2979 | |
| dc.language.iso | en | en_US |
| dc.publisher | Addis Ababa University | en_US |
| dc.subject | Surface Wave Dispresion | en_US |
| dc.title | Surface Wave Dispresion between North and East Africa | en_US |
| dc.type | Thesis | en_US |