Figure 6.
Conceptual model showing the inferred relationships between pressure pulses originated from subduction earthquakes and failure of pre-existing thrust faults in an accretionary margin. (a) Breaching of pressurised sectors along the ruptured subduction thrust induces pulses of overpressured crustal fluids channelled along adjacent, and steeper splay thrusts. (b) Composite Griffith-Coulomb failure envelope representing the shifting of initial stress states by a fluid pressure pulse localising fluid flow up-through a fault. The modality of failure depends on the differential stress magnitude. Half circles I and III represent different stress states required for producing frictional shear (I) and dilatant shear failure (III) on a 40°-dipping thrust fault. Dilatant shear failure on a 40°-dipping thrust needs a very small differential stress (half circle III), while a slightly larger stress state is necessary for a 30°-dipping thrust fault (half circle II). Both half circles II and III require a minimum principal stress lower than tensile strength of anisotropic material (TA), a condition that can be maintained only transiently (i.e., until when fluid pressure pulse overcomes fluid pressure loss caused by tensile fracturing). This figure was generated using Adobe Illustrator CS3 (https://www.adobe.com).