Seismicity and state of stress within the overriding plate of the Tonga‐Kermadec subduction zone

Abstract

[1] To reassess the main tectonic units and to quantify the slip partitioning within the overriding plate of the Tonga-Kermadec subduction zone, a seismotectonic study was performed using global seismicity and focal mechanisms catalogs. (1) New tectonic features were identified within the Lau Basin and the volcanic arc by remarkable shallow hypocenters alignments. (2) The Centroid Moment Tensor solutions catalog was processed in order to map the stress tensor variation in the upper plate. We found the tectonic features characterized by a diffuse seismicity are subjected to a composite stress regime and they are interpreted as diffuse immature plate boundaries controlled by the high thermal anomaly lying beneath the Lau Basin. (3) We quantified the margin-parallel rates of motion using the azimuth of the maximum compressive stress component computed within the interplate zone. The results highlight a major tectono-kinematic segmentation related to the subduction of the Louisville Seamount Chain. Citation: Bonnardot, M.-A., M. Régnier, E. Ruellan, C. Christova, and E. Tric (2007), Seismicity and state of stress within the overriding plate of the Tonga-Kermadec subduction zone, Tectonics, 26, TC5017,

Morphometric analysis of the submarine arc volcano Monowai (Tofua–Kermadec Arc) to decipher tectono-magmatic interactions

“…Furthermore, Graham et al (2008) determined the least compressive stress direction from elongation directions of the majority of the calderas to be northwest-southeast, consistent with a 122˚ rifting direction of magnitude 21 ± 5 mm yr⁻¹ at 28˚S (Pelletier and Louat, 1989). Accordingly the morphological expression of Kermadec Arc volcanism is influenced by the magnitude and direction of the local stress regime, which is dominantly transtensional (e.g., Delteil et al, 2002;Bonnardot et al, 2007).…”

Collisional model for rapid fore‐arc block rotations, arc curvature, and episodic back‐arc rifting in subduction settings

“…[50] An example of flattening as a result of fore-arc advance may occur in Tonga (Appendix A, Figure A3), where seismicity profiles taken across the Tonga subduction system show that the shallow portion of the slab dips less steeply in the north where trench retreat rates are highest (16°dip, near 18°S), compared to the south where retreat rates are lowest (27°dip near 23°S) [Bonnardot et al, 2007]. This flattening of the shallow portion of the slab beneath northern Tonga may be related to faster trench retreat at the northern Tonga Trench that is partially driven by the northern Tonga arc advancing more rapidly over the Pacific Plate, compared to the southern Tonga arc.…”

Structure and deformation of the Kermadec forearc in response to subduction of the Pacific oceanic plate

“…These volcanic arcs are continually being uplifted (Ballance et al 1989). Strike-slip and normal fault systems found on the western slope of the Tonga and Kermadec arcs reflect their oblique angle of subduction (Bonnardot et al 2007), while on-going extension in the Lau Basin and Havre Trough causes increasing separation of the arcs from their respective backarcs (Delteil et al 2002).…”

“…The most northwesterly and currently subducting seamount of the volcanic chain (which are commonly ∼2 km high and 10-40 km in diameter) causes a bathymetric discontinuity in the trench and at the lower-trench slope (Lonsdale 1988). This discontinuity divides the Tonga trench-forearc system to the north from the Kermadec trench-forearc system in the south (Karig 1970;Pelletier & Dupont 1990), and causes segmentation into the different tectonic regimes (Bonnardot et al 2007). The oblique strike (335…”

“…subducting plate (Dickinson & Seely 1979;von Huene & Scholl 1991). Variations in these characteristics often manifest themselves as changes in the dominant stress regime (Bonnardot et al 2007), and the rate of frontal and basal subduction erosion of the overriding plate (Clift & Vannucchi 2004;von Huene et al 2004). The LRSC and Hikurangi Plateau are thickened and buoyant regions of oceanic lithosphere, whose subduction is observed to have had a significant effect on the structural development of the forearc of the overriding plate (Collot & Davy 1998;Davy & Collot 2000;Contreras-Reyes et al 2011;Stratford et al 2014).…”