The geometry, kinematics and rates of deformation within a fault segment boundary between the ends of two major active normal fault segments have been investigated through examination of a faulted 126 ka marine terrace. Slip-vector azimuths defined by striations on the faults indicate N-S extension on c. E-W faults, sub-parallel to those from earthquake focal mechanisms, together with significant and contemporaneous E-W extension on c. N-S faults. Summed rates of E-W extension along a c. 550 m transect (0.17 mm/yr) are comparable with those for N-S extension (0.20 mm/yr) along a c. 350 m transect. Our observations show that distributed non-plane strain extension occurs in fault segment boundaries and this should be noted when studying fault-tip fracture toughness and regional deformation rates. ¿ 1997 American Geophysical Union