The tectonic structure and seismicity of West Antarctica from a regional seismic deployment
In this thesis I investigate the tectonic structure and seismicity of West Antarctica using recently deployed seismic networks. To study the crustal thickness of West Antarctica's constituent tectonic blocks, I model crustal shear-wave velocity structure using a joint inversion of receiver func...
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| Format: | Thesis |
| Language: | English |
| Published: |
2020
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| Online Access: | https://etheses.whiterose.ac.uk/28982/ https://etheses.whiterose.ac.uk/28982/1/Dunham_CKD_Earth_and_Environment_PhD_2020.pdf |
| Summary: | In this thesis I investigate the tectonic structure and seismicity of West Antarctica using recently deployed seismic networks. To study the crustal thickness of West Antarctica's constituent tectonic blocks, I model crustal shear-wave velocity structure using a joint inversion of receiver functions and Rayleigh wave phase velocity dispersion. I model crustal thickness from 30-38 km in the Antarctic Peninsula, and 38-40 km in the Haag-Ellsworth Whitmore block. Within the West Antarctic Rift System (WARS), I model a crustal thickness range of 18-28 km, and show that the thinnest crust is in the vicinity of the Byrd Subglacial Basin and Bentley Subglacial Trench. I find that the thin WARS crust extends towards the Pine Island Rift, suggesting that the northern boundary of the WARS lies in this region, ~200 km north of its previously accepted position. I additionally forward model high frequency receiver functions to assess if any thick, low velocity subglacial sediment accumulations are present, finding a 0.1-0.8 km thick layer at 10 stations. Such subglacial sediment could provide a source region for the soft basal till that acts to accelerate ice flow. To investigate the active processes occurring in West Antarctica I study local seismicity recorded from 2015-2018. I locate 86 events during this period, of which I categorise 32 as `likely tectonic', 17 as `likely ice-quakes' and 37 as `possible ice-quakes'. The distribution of events correlates well with modelled regions of high uplift resulting from Glacial Isostatic Adjustment. I also investigate styles and patterns of cryoseismicity produced by Pine Island Glacier, recorded at nearby stations from 2016-2018. High frequency (1-5 Hz) tremor produced by iceberg calving was detected at stations >250 km away from the glacier's calving front, whilst smaller repetitive seismicity produced by the destruction of the glacier's ice melange is also located. |
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