3.14 Komandorski section
The Komandorski section (Figure 6) extends ~530 km from near the western edge of Attu to the western end of the AASZ. Although this section is not included in the USGS NSHM, we include it here for completeness. There is no historical subduction interface rupture larger than Mw 6 or deeper than 50 km recorded along this section of the subduction zone (Kogan et al., 2017), nor is there active volcanism (Newberry et al., 1986). The 2017 Mw 7.8 earthquake near Komandorskiye Ostrova (also known as Komandorski Islands) in Russia ruptured nearly 400 km of the strike-slip Bering fracture zone between the Komandorski sliver and the Bering plate (Lay et al., 2017).
A substantial component of relative Pacific-Bering plate convergence is arc-parallel in the Komandorski section. Modeled geodetic observations indicate that lateral motion is accommodated along primarily along backarc strike-slip faulting as demonstrated in the 2017 Mw 7.8 rupture, but also as oblique convergence along the shallow subduction interface (Kogan et al., 2017; Lay et al., 2017). It is unclear if shallow interface slip is completely strike-slip as depicted in Lay et al. (2017), or if it is oblique or even occasionally trench-normal on the interface. Given the occurrence of subduction interface slip near the Andaman Islands (India) in the Mw 9.15 Sumatra–Andaman earthquake of 2004 where the Indian Plate converges obliquely under the Andaman Islands (Chlieh et al., 2007), we do not discard the idea that highly oblique relative plate convergence can lead to interface slip.
Geodetic observations in the Komandorski section can be fit with a model of a rigid Komandorski sliver moving westward at ~51 mm/year, bounded by the Aleutian subduction interface to the south and by the Bering fracture zone to the north (Kogan et al., 2017). Our calculation of relative Pacific - arc velocities (Table 2) indicates that as much as 38 mm/yr of convergence is available for interface slip. In the context of these models, we infer 100% coupling on the shallow subduction interface from the deformation front to a map distance of ~55 km arcward, corresponding to a depth of ~15 km (Figure 6).