Thermal and melt structure of the Juan de Fuca plate from ridge to trench to arc, inferred from seismic attenuation across the Amphibious Array

GSTDTAP

项目编号	1536566
	Thermal and melt structure of the Juan de Fuca plate from ridge to trench to arc, inferred from seismic attenuation across the Amphibious Array
	Geoffrey Abers
主持机构	Columbia University
项目开始年	2015
	2015-08-15
项目结束日期	2016-07-31
资助机构	US-NSF
项目类别	Standard Grant
项目经费	80480(USD)
国家	美国
语种	英语
英文摘要	The primary goal of this study is to better understand the mantle beneath tectonic plates that floor the ocean basins. The Cascadia Initiative deployed an Amphibious Array of seismic stations across the complete Juan de Fuca plate and adjacent Cascadia margin, in the Pacific Northwest. This is the first time a seismic array has covered a complete plate from spreading center to trench to volcanic arc. The cooling, rigid structure that characterizes an oceanic plate from its formation, through aging, and its eventual subduction at the continental margin is well understood. In contrast, the nature of the ductile, partially molten mantle underneath is less certain. Does melt occur in the mantle only beneath the magma-producing upwelling zone beneath the oceanic spreading center, or are small amounts of magma beneath the aging plate? As the plate approaches a trench and bends downward to subduct, does fracturing let seawater filter down into the plate, to be absorbed in minerals and carried into the mantle? If so, how and where do these volatiles later emerge to affect the fluidity of the slowly circulating mantle? The seismic analysis carried out in this study aims to answer these questions. A graduate student will carry out most of the analysis, expanding skills in a final PhD training year beyond what has already been gained in earlier thesis research. Although the thermal structure of oceanic lithosphere is well understood, basic questions regarding asthenosphere still exist. Both partial melt and bound water are proposed to explain low asthenosphere seismic velocities and viscosities but their distribution is not well constrained. It is not known if the base of the asthenosphere is defined by a constant pressure / homologous temperature, or if the asthenosphere is entrained at a subduction zone and carried to depth. Additional questions about temperature, water distribution and melt exist once plates subduct. This study focuses on seismic attenuation across the Cascadia Amphibious Array measured from body waves, since these physical properties can be better elucidated than from seismic velocity studies alone. Because the Amphibious Array provides such comprehensive broadband seismic data, the expected variations in body-wave attenuation can be seen here better than any other oceanic region. Comparisons with geodynamic models and with surface-wave derived images will allow calibration of laboratory-based theories of anelasticity.
来源学科分类	Geosciences - Ocean Sciences
文献类型	项目
条目标识符	http://119.78.100.173/C666/handle/2XK7JSWQ/68424
专题	环境与发展全球科技态势
推荐引用方式 GB/T 7714	Geoffrey Abers.Thermal and melt structure of the Juan de Fuca plate from ridge to trench to arc, inferred from seismic attenuation across the Amphibious Array.2015.