Abstract:

The layer of major seismic events in continental crust at the depth of the quartz brittle-plastic transition zone is called seismogenic zone. The crustal deformation of this zone, controlled by temperature and affected by strain rate and stress, plays an important role during seismic cycle. The major deformation mechanism is steady state creep during interseismic deformation, then changing to rupture at coseismic loading and transient creep at postseismic relaxation. However, most of the studies in the past were focused on intersceismic creep-related ductile deformation in natural fault and steady state creep tests under high temperature. There have been very limited studies on transient creep-related postseismic relaxation based on geological survey of brittle-plastic fault transition and experiments under high temperature and pressure. Especially, there is an absence of constitutive equations related to transient creep at postseismic relaxation. Fault slip research and GPS observation-based simulation of crustal deformation during postseismic depend on the transient creep test data and rheological model. In this study, we report our research progress on transient creep in brittle-ductile fault zone and under high temperature/pressure, analyze the deformation mechanism and models and discuss issues in quantitative calculation of fault strength for transient creep in brittle-ductile transition zone.

Key words: transient creep, postseismic relaxation, brittle-plastic transition