Small earthquakes in southern British Columbia : 1975-1991
| dc.contributor.author | Mulder, Taimi Lynn | en_US |
| dc.date.accessioned | 2024-08-14T22:55:04Z | |
| dc.date.available | 2024-08-14T22:55:04Z | |
| dc.date.copyright | 1995 | en_US |
| dc.date.issued | 1995 | |
| dc.degree.department | School of Earth and Ocean Sciences | |
| dc.degree.level | Master of Science M.Sc. | en |
| dc.description.abstract | Digital seismographs were first installed on the west coast of Canada in 1975. From 1981 to 1984 the seismic network expanded from the initial four stations to twenty-two stations. This provided a large database of digital data and well located earthquakes in southwestern British Columbia. In this thesis, the character of the seismicity in the North America plate was examined by calculating b-values (recurrence relationships) and Poisson's ratios for sub-regions of southwestern British Columbia and by investigating correlations of seismicity with geology, and with gravity and magnetic data. A rheological profile for the middle of the Strait of Georgia was calculated. One hundred and eleven focal mechanism solutions were computed from earthquakes in southwestern British Columbia from which the regional stress directions were determined (from P and T-axes). The following are the main conclusions from this study: 1. There is a bimodal earthquake distribution: a group of shallow events (< 10 km) and a group of deeper events (> 10 km), peaking around 20 km. In the Coast Plutonic Complex the majority of events are shallow, and beneath Vancouver Island the majority of events are deep(> 10 km). 2. The maximum regional compressive stress direction in southwestern British Columbia is north-northwest. The P-axes (maximum compressive stress) lie horizontally and dominate the focal mechanism solutions. The T-axes (minimum compressive stress) are oriented southsouthwest and have no preferential angle of inclination, which implies they are close to the same magnitude as the intermediate compressive stress. Together the P and T-axes suggest right-lateral shear or north-northwest compression. 3. Victoria area seismicity is not correlated with subsurface extensions of the Leech River, Survey Mountain, or Hurricane Ridge faults. | |
| dc.format.extent | 117 pages | |
| dc.identifier.uri | https://hdl.handle.net/1828/19064 | |
| dc.rights | Available to the World Wide Web | en_US |
| dc.title | Small earthquakes in southern British Columbia : 1975-1991 | en_US |
| dc.type | Thesis | en_US |
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