Rapid weakening of subducting plates from trench-parallel estimates of flexural rigidity
- 作者：Katrina M. Arredondo ; karredondo@ucdavis.edu ; Magali I. Billen mibillen@ucdavis.edu
- 关键词：Effective elastic thickness ; Oceanic lithosphere ; Plate bending ; Isostatic response ; Mantle convection ; Outer rise ; Gravity ; Energy dissipation ; Earthquakes ; Japan-Izu-Bonin Trench ; Kermadec Trench ; Tonga Trench ; Middle America Trench
- 刊名：Physics of the Earth and Planetary Interiors
- 出版年：2012
- 期刊代码：73_00319201
- 类别：ear
- 出版时间：April, 2012
- 卷：196-197
- 期：Complete
- 页码：1-13
- 文件大小：1099 K
摘要
The negative buoyancy force of sinking lithosphere (slabs) is the principle driving force for subducting plates, but transmission of this force to the subducting plate depends on the strength of the slab (e.g., ). Slab strength has been studied in the context of plate bending within subduction zones for a wide range of rheologies (i.e., perfectly elastic, perfectly viscous, perfectly plastic, brittle-ductile layered). Because the applicability of these rheologic models cannot be distinguished based on trench-perpendicular plate bending models (), a method was developed to directly measure variations in plate strength with distance from the trench and has found significant plate weakening within 100 km of the Kermadec Trench (). Using the same method we show that rapid plate weakening trenchward of the forebulge also exists at the Tonga and Japan-Izu-Bonin subduction zones. The observed plate weakening provides further evidence for a plate rheology that leads to significant yielding (loss of elastic strength and reduction in effective viscosity) within the bending region of the subducting plate. This rapid weakening within the shallow, low curvature, region of the plate may significantly decrease estimates of energy dissipation related to plate bending, compared to recent calculations assuming high plate strength and constant plate curvature.