The dextral Totschunda fault in southeast Alaska is a critical structure for transferring strain from the Fairweather plate boundary fault in the south to the intra-plate Denali fault to the west. However, the kinematics of this fault have been little studied. Based on reconnaissance work, Plafker et al. (1977) proposed a Holocene dextral slip rate of 1-2 cm/yr using offsets on supposed (but undated) late Wisconsin glacial deposits. This rate is consistent with a trilateration study along the southern Totschunda fault which estimated a smaller (but poorly-resolved) rate of ~1 cm/yr (Lisowski et al., 1987). For my proposed study, I will test these estimates by measuring the Quaternary slip rate along the southern / central Totschunda fault by employing geomorphic mapping of offset features (e.g. glacial moraines, debris flows, terraces, etc) and employ either radiocarbon or cosmogenic dating to obtain absolute ages. This data can then be used to test hypotheses about the role of the Totschunda fault in transferring strain and also help constrain the regional tectonic puzzle.

The regional importance of the Totschunda fault became apparent as a result of the 2002 M w 7.9 Denali earthquake, which ruptured both the central segment of the Denali fault and northern half of the Totschunda fault. To understand the regional kinematics of the Fairweather, Denali, and Totschunda faults, the variation in slip rate on the Totschunda fault must be determined. My proposed research will attempt to place the first hard constraint on the Quaternary slip rate on the southern Totschunda fault, while future work could focus on the northern segment. This will help answer questions about how strain is transferred between the Fairweather and Denali faults and also improve our understanding of how the lithosphere deforms by studying how strike slip fault systems interact and evolve. Lastly, my proposed research will also help quantify the potential for future large earthquakes within the vicinity of the Alaskan oil pipeline.