Rupture history of the Whirinaki fault, an active normal fault in the Taupo rift, new Zealand

Abstract

Trenching of two fault strands that form part of the 21 km long, and up to 2 km wide Whirinaki Fault, Taupo Rift, New Zealand, shows that surface fault rupture has occurred at least eight times during the past 26.5 kyr. Single-event displacements on each strand vary from a few decimetres to perhaps >2.5 m. Fault trace mapping, geomorphic analysis, and paleoseismic studies indicate a maximum magnitude for the Whirinaki Fault of c. M w 6.6, with a recurrence interval of between 1000 and 4000 yr. The variability of single-event displacement and timing of rupture on the two strands is attributed to various unsegmented and segmented rupture modes. Airfall tephra revealed in the trenches span the past 26.5 kyr, and provide time horizons to enable interpretation of how slip has accumulated on each of the strands of the fault. Temporal variation in slip rate ranges from 0.3 to 1.5 mm/yr and is indicative of spatial and temporal changes in the locus of strain in the Taupo Rift and the interdependence of the displacement rates and paleoearthquakes in the area.

National Seismic Hazard Model for New Zealand: 2010 Update

“…1). On land, many of the fault traces have been mapped in more detail and a number of new faults added, reflecting the large amount of new work on Taupo rift faults (Nairn et al, 2005;Villamor and Berryman, 2006a,b;Tronicke et al, 2006;Nicol et al, 2006;Villamor et al, 2007;Berryman et al, 2008;Canora-Catalan et al, 2008;Mouslopoulou et al, 2008;McClymont et al, 2008McClymont et al, , 2009Nicol et al, 2009;Begg and Mouslopoulou, 2010;Nicol et al, 2010;Villamor et al, 2011). The slip rates for many faults have also been refined, the largest change being the Rangipo fault (255,256,264,268), which has reduced from ∼3 to ∼0:2 mm=yr (Villamor et al, 2007).…”

“…Slip rates are well constrained for a number of on-land faults (e.g., Berryman et al, 1998;Berryman, 2001, 2006a;Villamor et al, 2007;Canora-Catalan et al, 2008;McClymont et al, 2009). However, where paleoseismic data are absent, on-land slip rates were inferred: (1) from faults along-strike, (2) as a proportion of the total extension rate along transects across the rift, and (3) from geomorphic expression.…”

Associations between volcanic eruptions from Okataina volcanic center and surface rupture of nearby active faults, Taupo rift, New Zealand: Insights into the nature of volcano-tectonic interactions

“…Fault rupture length based on fault continuity and geometry varies from a few kilometers to a maximum of 30 km, and fault dip-slip rates range from ~0.1 mm/yr to possibly 3 mm/yr Nicol et al, 2006;Berryman et al, 2008;Canora-Catalán et al, 2008). In many places, faults are 1-3 km apart (Figs.…”

“…3). We have used existing data (Berryman et al, 1998;Vil-lamor and Berryman, 2001;Zachariasen and Van Dissen, 2001;Berryman et al, 2002;Nairn et al, 2005;Villamor et al, 2007b;Canora-Catalán et al, 2008;McClymont et al, 2009) and new data, to investigate volcano-tectonic associations. These fault exposures partially characterize 16 major faults of the approximately 40 major faults in the area.…”

“…In the northern Taupo rift, the area of this study, despite a lack of historic volcano-tectonic interactions (see below), recent paleoseismological and geomorphic studies (e.g., Nairn et al, 2005;Villamor et al, 2007a;Berryman et al, 2008) have presented evidence of time associations between faulting and volcanism. Of particular interest in this study are those data that identify prehistoric temporal associations between a single volcanic eruption and rupture of a specifi c fault in the area around Okataina volcanic center in the past ~26,000 years Berryman et al, 2008;Canora-Catalán et al, 2008;Seebeck and Nicol, 2009). Although there is clear evidence of the coincidence in time and space of the two processes in the Taupo rift, the actual interaction mechanism is still poorly understood.…”