Browsing by Author "Purba, Joshua Chris Shadday"

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    Seismicity and tectonic interpretation of the Southern Rocky Mountain Trench near Valemount, British Columbia, Canada
    (2020-05-15) Purba, Joshua Chris Shadday; Dettmer, Jan; Gilbert, Hersh; Eaton, David William S.; Trad, Daniel O.
    The Rocky Mountain Trench is a large geological feature in the Canadian Cordillera with complex structures. Although efforts to understand the structure of the trench have been conducted through refraction-seismic, reflection-seismic, and geological studies, detailed knowledge of the trench is still sparse but crucial to understanding its evolution. Here, I conduct a local seismic study that involves earthquake detection, arrival-time picking, earthquake location, and a tectonic interpretation of the Rocky Mountain Trench in the area of Valemount, British Columbia. I developed and employed a nonlinear, probabilistic multiple-earthquake location for earthquakes detected here. The location provides both earthquake locations and rigorous estimates of their uncertainties. Based on analysing one year of data, my catalogue includes 47 local earthquakes that I identified and located. The results of the multiple-earthquake location presented here illustrates uncertainty reduction in depth from 18 to 5 km compared to the depths of earthquakes calculated based on single-earthquake locations. This lower depth uncertainty permits better inferences of the tectonic development of the Rocky Mountain Trench. The earthquake locations determined here displays a change in the distribution of seismicity around Valemount. Seismicity extends to the west of the RMT and the south of Valemount. While to the north, the seismicity is primarily confined to the trench and areas to the east. The distribution of seismicity also supports the dome-shaped Malton Gneiss in the subsurface. Seismic velocities are consistent with metamorphic rocks and the presence of significant amount of quartz in crustal rocks.