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

Abstract

We develop a kinematic model for the transition from subduction beneath the North Island, New Zealand, to strike‐slip in the South Island, constrained by GPS velocities and active fault slip data. To interpret these data, we use an approach that inverts the kinematic data for poles of rotation of tectonic blocks and the degree of interseismic coupling on faults in the region. Convergence related to the Hikurangi subduction margin becomes very low offshore of the northern South Island, indicating that in this region the majority of the relative plate motion has been transferred onto faults within the upper plate, as suggested by previous studies. This result has implications for understanding the likely extent of subduction interface earthquake rupture in central New Zealand. Easterly trending strike slip faults (such as the Boo Boo fault) are the key features that facilitate the transfer of strike‐slip motion from the northern South Island faults further north into the southern North Island and onto the Hikurangi subduction thrust. Our results also indicate that the transition from rapid forearc rotation adjacent to the Hikurangi subduction margin to a strike‐slip dominated plate boundary (with negligible vertical‐axis rotation) in the South Island occurs via a crustal‐scale hinge or kink in the upper plate, compatible with paleomagnetic and structural geological data. Despite the ongoing tectonic evolution of the central New Zealand region, our study highlights a remarkable consistency between data sets spanning decades (GPS), thousands of years (active faulting data), and millions of years (paleomagnetic data and bedrock structure).

Earthquake and Tsunami Potential of the Hikurangi Subduction Thrust, New Zealand: Insights from Paleoseismology, GPS, and Tsunami Modeling

“…Blue indicates areas of predicted subsidence, and red shows areas of uplift. The slip amounts used in the interseismically coupled area assume reversal of 800 years of accumulated slip deficit (using interseismic slip deficit rates from Wallace et al, 2012a; e.g., Figure 3), while the slip amounts within the SSE source area are tuned to produce vertical deformation consistent with that observed in Hawkes Bay paleoseismic studies (see Paleoearthquake and Paleotsunami Studies section in the text). Note that the use of 800 years of slip deficit does not imply an 800-year recurrence for such events, but rather provides a convenient way to assist with generation of distributed slip models.…”

“…Other interseismic coupling studies published prior to 2011 assumed steady aseismic creep at the Japan Trench Suwa et al, 2006;Hashimoto et al, 2009;Loveless and Meade, 2010) 174°E 175°E 176°E 177°E 178°E 179°E 139°E 140°E 141°E 142°E 144°E 145°E 146°E 143°E 41°S 40°S 39°S 38°S 37°S 41°N 40°N 39°N 38°N 37°N 36°N Figure 6. Comparison of interseismic coupling at the Hikurangi margin (left, Wallace et al, 2012a) and the Japan Trench offshore northern Honshu determined prior to the 2011 M W 9.0 earthquake (right, Wallace et al, 2009b) plotted at the same scale. Green contours on both are the coseismic slip distribution on the Japan Trench during the 2011 M W 9.0 earthquake from GPS (Simons et al, 2011), and the yellow star shows the earthquake's epicenter.…”

“…Gray dots = continuous GPS sites (http://www.geonet.org.nz). Arrows show convergence rates at the trench in mm yr -1 (Wallace et al, 2012a believed to splay from the subduction interface at a depth of about 20-30 km (King et al, 2007;McFadgen, 2008). The name, which translates to "land-swallower, "…”

Evidence for Past Subduction Earthquakes at a Plate Boundary with Widespread Upper Plate Faulting: Southern Hikurangi Margin, New Zealand

“…Geodetic data show the plate interface beneath the southern North Island is currently interseismically coupled ( Fig. 1; Wallace et al, 2012) and accumulating a slip rate deficit of 20-25 mm=yr. The strongly coupled patch on the plate interface from Cook Strait to Cape Turnagain has been suggested by Wallace et al (2009) as a likely rupture area for an M w 8.5-8.7 plate interface earthquake.…”

Chronostratigraphy of the Hottah terrane and Great Bear magmatic zone of Wopmay Orogen, Canada, and exploration of a terrane translation model

“…Basin opening and strike-slip translation have also been related to the evolution of thick-slab subduction that transitions to strike-slip faulting in Alaska, also over a short time period (Trop et al 2012). The Taupo volcanic zone analogy is another example of upper-plate extension, driven by slab rollback, within a complex arc -back-arc environment adjacent to the transition of the subduction zone to a large-scale transtensional shear zone -the Alpine fault (e.g., Wallace et al 2012;Giba et al 2013).…”