Frictional and Lithological Controls on Shallow Slow Slip at the Northern Hikurangi Margin. (9th February 2022)

• Record Type: Journal Article
• Authors: Shreedharan, Srisharan; Ikari, Matt; Wood, Clay; Saffer, Demian; Wallace, Laura; Marone, Chris
• Is Part Of: Geochemistry, geophysics, geosystems. Volume 23:Number 2(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-02-09
• Subjects: slow earthquakes -- Hikurangi -- friction -- slow slip; Geochemistry -- Periodicals; Geophysics -- Periodicals; Earth sciences -- Periodicals; 550.5
• DOI: 10.1029/2021GC010107
• Languages: English
• ISSNs: 1525-2027

Abstract

Abstract: Slow slip events (SSEs) have been identified at subduction zones globally as an important link in the continuum between elastodynamic ruptures and stable creep. The northern Hikurangi margin is home to shallow SSEs which propagate to within 2 km of the seafloor and possibly to the trench, providing insights into the physical conditions conducive to SSE behavior. We report on a suite of friction experiments performed on protolith material entering the SSE source region at the Hikurangi margin, collected during the International Ocean Discovery Program Expedition 375. We performed velocity stepping and slide‐hold‐slide experiments over a range of fault slip rates, from plate rate (5 cm/yr or 1.6 × 10 −9 m/s) to ∼1 mm/s (10 −3 m/s) and quantified the frictional velocity dependence and healing rates for a range of lithologies atdifferent stresses. The frictional velocity dependence ( a‐b ) and critical slip distance DC increase with fault slip rate in our experiments. We observe atransition from velocity weakening to strengthening at slip rates of ∼0.3 µm/s. This velocity dependence of DC could be due to a combination of dilatant strengthening and a widening of the active shear zone at higher slip rates. We document low healing rates in the clay‐rich volcaniclastic conglomerates, which lie above the incoming plate basement at least locally, and relatively higher healing rates in the chalk lithology. Finally, our experimental constraints on healing rates in different input lithologies extrapolated to timescales of 1–10 years are consistent with the geodetically inferred low stress drops and healing rates characteristic of the Hikurangi SSEs. Key Points: We quantify frictional stability and healing behavior of input material to the subduction plate interface at the northern Hikurangi margin Increasing frictional stability and critical slip distance with velocity may be key mechanisms responsible for shallow slow slip Velocity dependence of critical slip distance may be from a combination of dilatant strengthening and distributed slip at higher slip rates