Sharp thermal transition in the forearc mantle wedge as a consequence of nonlinear mantle wedge flow

• Published in: Geophysical research letters Vol. 38; no. 13
• Main Authors: Wada, Ikuko, Rychert, Catherine A., Wang, Kelin
• Format: Journal Article
• Language: English
• Published: Washington, DC Blackwell Publishing Ltd 01-07-2011; American Geophysical Union
• Subjects: Earth sciences; Earth, ocean, space; Exact sciences and technology; mantle rheology; mantle wedge; seismic attenuation; subduction zone; thermal structure; Temperature dependence; interfaces; attenuation; rheology; dip; Thick plate; Modeling; lead; Onset time; Feedback; mantle; Flow velocity; subduction zones; flow field; Timing; slabs; flow
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2011GL047705

In the forearc mantle wedge, the thermal field depends strongly on slab‐driven mantle wedge flow. The flow is in turn affected by the thermal field via the temperature dependence of mantle rheology. Using thermal modeling, we show that the nonlinear feedback between the thermal and flow fields always leads to complete stagnation of the mantle wedge over a shallow, weakened part of the slab‐mantle interface and an abrupt onset of mantle flow further down‐dip. The abrupt increase in flow velocity leads to a sharp thermal transition from a cold stagnant to a hot flowing part of the wedge. This sharp thermal transition is inherent to all subduction zones, explaining a commonly observed sharp arc‐ward increase in seismic attenuation.
Key Points
The temperature dependence of mantle rheology causes nonlinear wedge flow
The nonlinear wedge flow always results in a sharp thermal transition
The thermal transition can explain the observed change in seismic attenuation