Timing of late Holocene surface rupture of the Wairau Fault, Marlborough, New Zealand

Abstract

Three trenches excavated across the central portion of the right-lateral strike-slip Wairau Fault in South Island, New Zealand, exposed a complex set of fault strands that have displaced a sequence of late Holocene alluvial and colluvial deposits. Abundant charcoal fragments provide age control for various stratigraphic horizons dating back to c. 5610 yr ago. Faulting relations from the Wadsworth trench show that the most recent surface rupture event occurred at least 1290 yr and at most 2740 yr ago. Drowned trees in landslide-dammed Lake Chalice, in combination with charcoal from the base of an unfaulted colluvial wedge at Wadsworth trench, suggest a narrower time bracket for this event of 1811-2301 cal. yr BP The penultimate faulting event occurred between c. 2370 and 3380 yr, and possibly near 2680 ± 60 cal. yr BP, when data from both the Wadsworth and Dillon trenches are combined. Two older events have been recognised from Dillon trench but remain poorly dated. A probable elapsed time of at least 1811 yr since the last surface rupture, and an average slip rate estimate for the Wairau Fault of 3-5 mm/yr, suggests that at least 5.4 m and up to 11.5 m of elastic shear strain has accumulated since the last rupture. This is near to or greater than the single-event displacement estimates of 5-7 m. The average recurrence interval for surface rupture of the fault determined from the trench data is 1150-1400 yr. Although the uncertainties in the timing of faulting events and variability in inter-event times remain high, the time elapsed since the last event is in the order of 1-2 times the average recurrence interval, implying that the Wairau Fault is near the end of its interseismic period.

Mid‐late Holocene paleoseismicity of the eastern Clarence Fault, Marlborough, New Zealand

“…Comparisons with other Marlborough faults estimates for the middle Clarence valley section of the Clarence Fault of average recurrence interval (c. 1700 yr), singleevent surface-rupture displacement (7 ± 2 m), and lateral slip rate (c. 4 mm/yr) are similar, within a factor of <2, to published estimates of these values for the northern two Marlborough faults-the Wairau Fault (e.g., Lensen 1976;Knuepfer 1992;Zachariasen et al 2001Zachariasen et al , 2006 and the Awatere Fault (e.g., McCalpin 1996b; Hill et al 2000;Benson et al 2001;Mason & Little 2006;Mason et al 2006a,b). However, they are significantly different from those of the Hope Fault to the south, which has a much higher slip rate and a shorter recurrence interval (Cowan 1990;Cowan & McGlone 1991;Van Dissen & Yeats 1991;Knuepfer 1992;Pettinga et al 2001;Langridge et al 2003).…”

“…By comparison, the middle Clarence valley section of the Clarence Fault has not ruptured within the last c. 1700-1900 yr, and the elapsed time since the most recent rupture is similar to its average recurrence interval. Zachariasen et al (2001Zachariasen et al ( , 2006 comment that there is no geological evidence, to date, suggesting that ruptures on any one Marlborough fault causally relate to ruptures on any other Marlborough fault. If this is the case, then it is probably a consequence of both the orientation and sense of slip of the faults relative to each other.…”

The kinematics of a transition from subduction to strike‐slip: An example from the central New Zealand plate boundary

“…Where the Marlborough faults take on a more northerly strike the deformation involves a greater convergent component (e.g., Jordan Thrust) [ Van Dissen and Yeats , 1991]. The Awatere, Clarence and Wairau faults each have slip rates ranging from 4 to 8 mm/yr [ Benson et al , 2001; Mason et al , 2006; Zachariasen et al , 2006; Van Dissen and Nicol , 2009], while the Hope Fault is slipping at 13–23 mm/yr or more [ Van Dissen and Yeats , 1991; Langridge et al , 2003; Langridge and Berryman , 2005]. There is a general decrease in age of the Marlborough Faults southward: the Awatere Fault activity started ∼5.5–6.2 Ma [ Little and Jones , 1998], the Clarence Fault initiated at ∼3 Ma [ Browne , 1992], and initiation of the Hope Fault occurred ∼1–2 Ma [ Langridge and Berryman , 2005; Wood et al , 1994; R. Langridge, unpublished data, 2011].…”

Investigating subduction earthquake geology along the southern Hikurangi margin using palaeoenvironmental histories of intertidal inlets

“…If correct, the coseismic unit may be associated with a subduction earthquake that produced shaking and a tsunami but no significant upper plate subsidence, or it could have been caused by an event on a nearby upper plate fault. Both the Wairau and Vernon Faults have been active during the Holocene so are candidates for causing strong shaking at Big Lagoon (Zachariasen et al 2006;Pondard & Barnes 2010).…”