A new analytic model is presented for the thermal structure of subduction zones. It applies to the deeper regions of a subduction zone, where the overriding mantle is no longer rigid but flows parallel to the slab surface. The model captures the development of one thermal boundary layer out into the mantle wedge, and another into the subducting slab. By combining this model with the analytic mo...

Double seismic zones are two-layered distributions of intermediate-depth earthquakes that provide insight into the thermomechanical state of subducting slabs. We present new precise hypocenters of intermediate-depth earthquakes in the Tonga subduction zone obtained using data from local island-based, ocean-bottom, and global seismographs. The results show a downdip compressional upper plane and...

Deep earthquakes have been a paradox since their discovery in the 1920s. The combined increase of pressure and temperature with depth precludes brittle failure or frictional sliding beyond a few tens of kilometers, yet earthquakes occur continually in subduction zones to approximately 700 km. The expected healing effects of pressure and temperature and growing amounts of seismic and experimenta...

Introduction Hydrothermal systems and their associated metal deposits have been studied at oceanic spreading centers since the late 1970s when they were first discovered. More recently, those studies have been extended to subduction zone hydrothermal systems including active volcanic arcs and back-arc environments. Oceanic spreading centers compose a global ridge system where new ocean crust is...

Primarily aseismic deformation transients in subduction zones, sometimes associated with tremors and low-frequency earthquakes, are a newly recognized mode of deformation. Stressing in the up-dip seismogenic zone is increased episodically due to down-dip transient slips, and each eventmaymake itmore prone to failure in a large thrust earthquake. It is important for seismic hazard assessment to ...

Before its collision with Eurasia1–5, the Indian Plate moved rapidly, at rates exceeding 140mmyr−1 for a period of 20 million years1,3–7. This motion is 50 to 100% faster than the maximum sustained rate of convergence of themain tectonic plates today8. The cause of such high rates of convergence is unclear and not reproduced by numerical models9,10. Here we show that existing geological data11,...

[1] We expand the theory of critically tapered Coulomb wedge for accretionary prisms by considering stress changes in subduction earthquake cycles. Building on the Coulomb plasticity of the classical theory, we assume an elastic–perfectly Coulomb plastic rheology and derive exact stress solutions for stable and critical wedges. The new theory postulates that the actively deforming, most seaward...

[1] Adakitic melts from Papua New Guinea (PNG) show adakitic geochemical characteristics, yet their geodynamic context is unclear. Modern adakites are associated with hot-slab melting and/or remelting of orogenic mafic underplate at convergent margins. Rift-propagation over collision-modified lithosphere may explain the PNG adakite enigma, as PNG was influenced by rapid creation and subduction ...

Atmospheric carbon dioxide (CO2) data for the last 420 million years (My) show long-term fluctuations related to supercontinent cycles as well as shorter cycles at 26 to 32 My whose origin is unknown. Periodicities of 26 to 30 My occur in diverse geological phenomena including mass extinctions, flood basalt volcanism, ocean anoxic events, deposition of massive evaporites, sequence boundaries, a...

Understanding variations of slip distance along major thrust systems at convergent margins is an important issue for evaluation of near-trench slip and the potential generation of large tsunamis. We derived quantitative estimates of slip along ancient subduction fault systems by using the maturity of carbonaceous material (CM) of discrete slip zones as a proxy for temperature. We first obtained...