Linking Visco‐Elasto‐Plastic Modeling of Recent Slab Deformation to Present‐Day Deep Earthquakes

Abstract Deep earthquakes require the cold temperatures found in sinking lithosphere to store elastic strain. It has also been proposed that sufficiently high rates of deformation are also required, regardless of the failure mechanism. However, this strain‐rate hypothesis is based on generic time‐dependent and visco‐plastic subduction models, positing a challenge for direct comparisons to present‐day earthquake observations. Here, we present a new numerical modeling approach incorporating location‐specific visco‐elasto‐plastic models to facilitate direct comparison with deep earthquake observations. We present a Proof‐of‐Concept Model using a 2D synthetic slab to demonstrate that this novel approach can reproduce stress and strain‐rate patterns and the stress orientations from a fully time‐dependent model. Applying this method to a 2D profile through the Tonga‐Kermadec subduction zone we find that variations in strain‐rate correlate with seismicity rate and regions of stress in the slab exceeding 500 MPa. Elasticity in the slab leads to formation of a clearly defined neutral plane extending into the transition zone and creating a narrow region of down‐dip compression along the top portion of the slab which broadens across the full width of the slab only within the deep transition zone. In addition, assuming that the strain‐rate hypothesis is correct, we show that peaks in strain‐rate, which are associated with bends in the slab, could be used to constrain the slab shape beyond the envelope of seismicity.