Localized vs distributed deformation associated with the linkage history of an active normal fault, Whakatane Graben, New Zealand

The deformation associated with an active normal fault is investigated at a high temporal resolution (c. 104 yr). The Rangitaiki Fault (Whakatane Graben, New Zealand) and its adjacent faults accommodated an overall extension of ∼0.83% oriented at ∼N324°E over the past 17 kyr. This is consistent along strike, but the pattern of faulting that accommodates this strain defines two different spatial domains. To the SW, one domain is characterized by a few large faults, with >80% of strain localized onto geometrically and kinematically linked segments of the main fault. This produces marked heterogeneity in the spatial distribution of strain across the graben. In contrast, to the NE, a domain of distributed faulting is characterized by numerous small faults contributing to the overall deformation, with only ∼35% of strain localized onto the Rangitaiki Fault. The transition from distributed to localized deformation is attributed to an increase in linkage maturity of the Rangitaiki Fault. Progressive strain localization has been ongoing within the network over the last 17 kyr, with localization of fault activity increasing by ∼12%, indicating this process occurs over kyr time periods that only reflect a few earthquake events.