Project title: The link between stress, fluid flow, and subduction dynamics: Implications for offshore geohazards and resource development
Researcher: Effat Behboudi
Over the past decade, Hikurangi Subduction Margin (HSM) has gained increased research attention due to earthquake ruptures and shallow Slow Slip Events (SSEs) along the plate interface. Shallow (< 2-15 km from the seafloor), episodic SSEs are recurring every 18-24 months over a period of 2-3 weeks between the deep steadily slipping zones and the shallow locked portion of the subduction interface at North of HSM (Wallace et al., 2020; Figure 1). It has been suggested that SSEs may play a critical role in triggering damaging earthquakes and tsunamis by redistributing and increasing stress in shallow seismogenic zones where the subduction interface is locked (Voss et al., 2018). On the other hand, SSEs could reduce the probability of large earthquakes by relieving strain and reducing the magnitude of coseismic slip (Voss et al., 2018). However the physical mechanism of SSEs and the role of the upper plate in coupling behaviour of subduction are not completely understood. To assess seismic hazards and improve our understanding of active crustal deformation, geodynamic processes and seismicity in tectonically active regions such as the Hikurangi subduction margin, the knowledge of upper crustal stress, tectonic structure, pore pressure, and geomechanical properties of HSM’s hangingwall is crucial.
Hypothesis: The stress state of the Hikurangi Subduction Margin varies along and across strike and this plays a role in the variable seismic behaviour across this subduction zone.
• To quantify the in-situ stress state and its variation along and across strike of the Hikurangi Subduction Margin.
• To determine the relationship between stress state and subduction dynamics and the role of this in seismic behavior.
• To develop a geomechanical model of aspects of the subduction margin that will inform hazard modelling and resource development planning.
• Determine the stress orientation and its variability within the shallow upper crust of the subduction margin hangingwall.
• Quantify the full in-situ crustal stress tensor and its variation along and across the strike of Hikurangi Subduction Margin and build a 1D geomechanical model.
• Investigate likely links between stress state and coupling behaviour of the subduction interface, geological structure (faults and fractures), lithological properties, and pore pressure variation within the hangingwall of Hikurangi subduction interface.
• Perform fault slip tendency analysis for selected structures across the HSM using our stress model to understand their potential seismic behaviours.