Rough Subducting Seafloor Reduces Interseismic Coupling and Mega‐Earthquake Occurrence: Insights From Analogue Models

Abstract

The roughness of the subduction interface is thought to influence seismogenic behavior in subduction zones, but a detailed understanding of how such roughness affects the state of stress along the subduction megathrust is still debated. Here, we use seismotectonic analogue models to investigate the effect of subduction interface roughness on seismicity in subduction zones. We compared analogue earthquake source parameters and slip distributions for two roughness endmembers. Models characterized by a very rough interface have lower integrated fault strength and lower interseismic coupling than models with a smooth interface. Overall, ruptures in the rough models have smaller rupture area, duration, and mean displacement. Individual slip distributions indicate a segmentation of the subduction interface by the rough geometry. We propose that flexure of the overriding plate is one of the mechanisms that contribute to a heterogeneous stress distribution, responsible for the observed seismic behavior.

Kinetic Models for Healing of the Subduction Interface Based on Observations of Ancient Accretionary Complexes

“…Some subduction interface earthquakes seem to have asperities that coincide with subducting bathymetric features such as seamounts (Abercrombie et al, 2001;Bilek et al, 2003;Collot et al, 2017;Husen et al, 2002). However, the greatest subduction zone earthquakes are correlated with smooth subducting interfaces and thick subducting sediment piles (Lallemand et al, 2018;van Rijsingen et al, 2019;Scholl et al, 2015). Moreover, in records of repeated earthquake cycles from microatoll records from Sumatra, the arrangement of asperities can change from event to event (Philibosian et al, 2017).…”

“…The relationship between crack sealing via silica kinetics and fault zone slip behavior can be understood in terms of the influence of crack healing on frictional properties and the local fault zone stiffness. The mode of frictional sliding is dictated by the ratio of the fault stiffness, K, and the rate of fault weakening with slip, which defines a critical rheologic stiffness, K c (Rice & Ruina, 1983), that can be written…”

Coupled Evolution of Deformation, Pore Fluid Pressure, and Fluid Flow in Shallow Subduction Forearcs

“…The overall conceptual picture is one of a structurally disrupted upper plate, a highly heterogeneous stress state, pervasive shearing and fracturing promoted by the irregular geometry, and spatially complex patterns of basal erosion and material underplating. These effects have been investigated by several numerical and laboratory analogue modeling studies (Ding & Lin, 2016; Morgan & Bangs, 2017; Ruh et al, 2016; van Rijsingen et al, 2019). Our model (in Figure 8) differs from most existing numerical studies by explicitly incorporating the effects of fluid drainage and its interplay with deformation processes including geometrically modulated tectonic loading and stress‐dependent sediment compaction.…”

“…Moreover, the higher the basement relief (from 100 m in RB1 to 300 m in RB3), the greater the departure from the theoretical expectation for a smooth interface (Figure 8c). In other words, when the subducting basement is rough, the wedge morphology will respond as if the detachment is mechanically stronger-a phenomenon that has been qualitatively documented in laboratory analogue studies (e.g., Gutscher et al, 1996;van Rijsingen et al, 2019). Compared with the general trend reflected by our "smooth and weak" models (white symbols in Figure 8b, right panel), modeled subduction forearcs with either rough basement (models RB1-3) or strong décollement material (SD1-3) exhibit high wedge tapers.…”

Fault slip envelope: a new parametric investigation tool for fault slip based on geomechanics and 3-D fault geometry

“…In the example of Olkiluoto, uncertainties in fault surface geometry were estimated from a significant amount of data available from bore hole, seismic profiles, tunnel wall observations, and outcrop measurements (Mattila et al, 2008). Truncation bias is here defined by not considering the faults smaller than 100 m length estimated to allow incremental displacement lower than 10 −2 m (Wells and Coppersmith, 1994). Variability or uncertainty in in situ stresses and rock material properties estimated from bore hole and rock tests are not considered limitations since they are used to constrain their range of variability in the parametric study (see Sect.…”