| Title | Soft soil response investigations in Kitimat, BC - some preliminary results |
| |
| Author | Crow, H L ;
Hunter, J; Brewer, K; Brillon, C; Cote, M; Allen, T; Cassidy, J F; Hayek, S |
| Source | Proceedings of the 11th Canadian Conference on Earthquake Engineering (11th CCEE); by Canadian Association for Earthquake Engineering; Earthquake Engineering and Engineering Vibration 2015, 9
pages |
| Links | Online - En ligne
(ResearchGate)
|
| Year | 2015 |
| Alt Series | Earth Sciences Sector, Contribution Series 20150034 |
| Meeting | 11th Canadian Conference on Earthquake Engineering (CCEE); Victoria; CA; July 21-24, 2015 |
| Document | serial |
| Lang. | English |
| Media | paper |
| File format | doc |
| Province | British Columbia |
| NTS | 103I/02 |
| Area | Kitimat |
| Lat/Long WENS | -128.7500 -128.5000 54.0833 54.0000 |
| Subjects | soils science; geophysics; soil studies; seismic interpretations; glacial deposits; seismic surveys; earthquakes; fluvial deposits; marine sediments |
| Illustrations | location maps; seismic maps; seismic velocity profiles; seismic profiles; tables; graphs |
| Program | Marine Geohazards Mapping & Monitoring (MGMM) |
| Released | 2015 01 01 |
| Abstract | The north coast town of Kitimat, BC is located in a zone of moderate seismic hazard, relative to high-hazard regions of southwest BC. The town is underlain by a valley filled with unlithified glacial,
soft fluvial, and marine sediments deposited on firm bedrock. Such settings are commonly prone to earthquake ground motion amplification and resonance effects. Reconnaissance field surveys were conducted to measure resonance effects in areas of thick
soft soil. Results indicate substantial Horizontal-to-Vertical Spectral Ratio (HVSR) peaks at frequencies as low as 0.41 Hz using a portable seismograph. During these surveys, a local MW 4.6 earthquake occurred to the west of Haida Gwaii (275 km
away) and was recorded by both the portable seismograph at a soft soil site and at a bedrock site 2.5 km away. Comparisons of the time histories showed considerable amplitude and frequency differences between the soil and rock sites. At the soil
site, an HVSR resonant peak amplitude of 8 was recorded at 0.84 Hz during ambient noise measurements, whereas an HVSR peak amplitude of 21 was observed from the surface-wave portion of the earthquake event. Particle-motion plots of various portions
of the earthquake time series at the soil site showed several packets of late arriving "valley-generated" surface waves at the site resonance frequency which were not observed at the rock site. These preliminary results demonstrate the importance of
conducting additional site response investigations in this region. |
| Summary | (Plain Language Summary, not published)
The north coast town of Kitimat, British Columbia, is located in a zone of moderate seismic hazard. The town is underlain by a valley filled with
unconsolidated glacial, soft fluvial, and marine sediments deposited on firm bedrock. Such settings are commonly prone to earthquake ground motion amplification and resonance effects. Field surveys were conducted to measure resonance effects in areas
of thick soft soil. Results indicate substantial Horizontal-to-Vertical Spectral Ratio (HVSR) peaks at frequencies as low as 0.41 Hz using a portable seismograph. During these surveys, a local Mw4.6 earthquake occurred offshore Haida Gwaii (275 km
west) and was recorded by both the portable seismograph at a soft soil site and at a bedrock site 2.5 km away. Comparisons of the time histories showed considerable amplitude and frequency differences between soil and rock. |
| GEOSCAN ID | 296374 |
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