3.5 Kodiak section
The Kodiak section (Figure 3) extends ~310 km along Kodiak Island to just beyond the Trinity Islands and encompasses a major slip patch in the CE 1964 rupture (Ichinose et al., 2007; Suito & Freymueller, 2009). The Kodiak section also exhibits a larger area of high interseismic coupling than the adjacent Barren Islands and Kenai sections (Li et al., 2016). The slab dip beneath Kodiak is steeper, and the seismogenic interface correspondingly narrower, than the neighboring Barren Islands, Kenai, and Prince William Sound sections (Hayes et al., 2018). Slip in 1964 terminated near Sitkinak Island southwest of Kodiak (Briggs et al., 2014; Plafker, 1969), corresponding roughly with the intersection of the Aja fracture zone and the accretionary prism (von Huene et al., 1999).
The Kodiak section has been the focus of many detailed paleoseismic investigations (Carver & Plafker, 2008; Gilpin, 1995; Gilpin et al., 1994; Shennan et al., 2014). Shennan et al. (2018) summarize evidence for five Kodiak-section-wide land-level changes between 1964 CE and ~1500 BP, including the historical penultimate event in1788, resulting in a mean closed-interval recurrence of ~379 years (Table 1). Observations from sites spanning the 1964 rupture zone indicate that the Kodiak section typically ruptures independently of the Prince William Sound section (Shennan et al., 2018).
Geodetic observations along the Kodiak section are consistent with a highly coupled interface beneath Kodiak Island (Drooff & Freymueller, 2021; Li et al., 2016; Li & Freymueller, 2018). Here we generalize the geodetic models into 100% coupling extending ~175 from the deformation front, corresponding to a locking depth of ~30km on the plate interface (Figure 3).