Box 1 Splay Fractures Associated with Strike-slip Faults and Their Properties‌‌

This box highlights the length and angular characteristics of splays associated with strike-slip faults, along with their controlling parameters, primarily from de Joussineau and others (2007). These geometrical characteristics are relevant for groundwater flow in aquifers as they govern the distance at which splays extend from their parent faults and their angle to them. There is a clear positive correlation between the splay length and the parent fault length: the longer the fault, the longer the splays. The splay length also depends on the remote principal stress ratio: it increases with increasing stress ratio.

The angle that splays make with their parent fault, called the kink angle, depends on the fault configuration and the stress regime. If faults are isolated, their splays make a small angle with the parent fault, typically on the order of 20-30°. Conversely, if faults are located close to one another and could mechanically interact, the splays tend to form at a higher angle with their parent fault, typically above 40°. Finally, as is the case for splay length, the stress regime acting at the time of formation of splays impacts their angular relationships with their parent fault. A wide range of kink angles is possible depending on the confining pressure, the principal stress ratio and the angle of the parent fault with the maximum principal stress.

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