Streak Tectonics associated with the Irregular Slab Topography at Subduction Zones

Abstract:

We demonstrate the physical features of streak tectonics (or abrasion tectonics) associated with the irregular surface topography, such as local convex rise or seamount(s), on the downgoing slab at subduction zones.

Marine surveys such as sophisticated multichannel seismic experiments have revealed the detailed vertical structure of the overriding lithosphere as well as the upper-most part of downgoing slab at the fore-arc zone from the trench axis through the inclined plate interface zone at a depth of 10 - 15km.

As previously, some researchers (e.g., Eguchi, 1979, 1996; Hilde, 1983; Suzan, 2010) demonstrated the influence of the surface irregular topography of the slab on the occurrence regime of greater interplate seismic events with the low-angle underthrusting slip.

However, the earlier studies didn’t incorporate any effects due to the spherical buckling of oceanic lithosphere with the age-dependent elastic thickness at subduction zones.

In the case of a subduction zone where the slab age has gradually been decreasing or increasing, the spherical buckling of elastic shell (e.g., Eguchi, 2012) suggests that the interplate mechanical coupling strength varies with time and space.

Next, we argue some tectonic features of strain-rate dependent deformation at areas surrounding an isolated-seamount on the downgoing slab, such as the quasi-static fluid lubrication, boundary lubrication or plastic deformation.

We then discuss how to represent mathematically the streak process during a larger interplate seismic event at the non-uniform plate interface zone.