Extension and Quaternary Faulting in the Northern Central Nevada Seismic Belt
AdvisorWesnousky, Steven G.
Geological Sciences and Engineering
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Quaternary mapping of seven sites along the 1915 MS 7.7 Pleasant Valleyearthquake and one site on the 1954 MS 6.8 Dixie Valley earthquake is the basis todescribe the style and rate of faulting in the northern Central Nevada Seismic Belt.Cosmogenic depth profiles collected on alluvial surfaces displaced by multipleearthquakes at Siard Canyon in Pleasant Valley and Terrace Creek in Dixie Valley areanalyzed to show the Pleasant Valley and Terrace Creek surfaces where abandoned ~110ka and ~70 ka ago, respectively. The Pleasant Valley and Terraces Creek surfaces aredisplaced to exhibit vertical separations of 5.6 ± 0.5 and 34.6 ± 1.0 meters, respectively.Dividing the offsets observed at each site by the ages of fan abandonment at each siteyields estimates of the vertical slip rate equal to 0.47 (0.26-0.83) mm/yr at Terrace Creekin Dixie Valley, and 0.05 (0.03-0.07) mm/yr at Siard Canyon in Pleasant Valley.Diffusion modeling of scarp profiles at two sites within Pleasant Valley show the lastearthquake to rupture the Pleasant valley fault occurred ~14 – 27 ka before 1915.Reoccupation and remapping of 7 sites previously studied by Wallace, 1984 shows thatthe direction of crustal extension accommodated during the 1915 earthquake is orientedbetween 308.4° ± 12.5° and 294.2° ± 9.3°.