Strikeslip

Strikeslip, in geology, refers to a fault on which the dominant displacement is horizontal, parallel to the strike of the fault. Movement occurs as blocks slide past one another, with little vertical displacement. Strikeslip faults are a primary mechanism of crustal deformation at transform plate boundaries and in zones of oblique collision. They are categorized into right-lateral (dextral) and left-lateral (sinistral) faults, depending on the direction the opposite side moves relative to an observer on one block facing the fault.

These faults form where shear stress causes lateral shear of crust, and they can occur in continental interiors and along mid-ocean ridges. Surface exposure can show linear fault traces, sag ponds, or offset streams. In some settings, strike-slip motion is accommodated by steps or bends in the fault, producing pull-apart basins or restraining and releasing bends.

Prominent examples include the San Andreas Fault system in California, the Alpine Fault in New Zealand, and the North Anatolian Fault in Turkey. Slip rates vary from a few millimeters to tens of millimeters per year and can be episodic during earthquakes.

Modern methods such as GPS geodesy, InSAR, and paleoseismology are used to measure slip rates, rupture history, and earthquake recurrence. Strikeslip faults interact with other fault types and can transfer stress between fault segments, influencing regional seismic hazard.

See also: strike-slip fault, transform fault, oblique-slip fault.