Collaborative Research: Active Tectonics at the Aleutian-Kamchatka Corner -- A Lithospheric Perspective

这是科罗拉多大学和耶鲁大学的主要研究人员合作提出的建议。北极构造是由北美、欧亚和太平洋板块的相互作用主导的。在海洋地区，这些板块之间的边界相对来说是众所周知的，但北美-欧亚板块的边界在很大程度上是由一个广泛的大陆内部变形带确定的。这种变形的驱动机制尚不清楚。新获得的地震数据使破译阿留申-堪察加交界处的板块运动成为可能。这个连接处连接了沿阿留申群岛西部的走滑白令断层和堪察加半岛南部的一个活跃俯冲带，在那里板块汇聚伴随着活跃的弧火山活动。鄂霍次克海位于堪察加俯冲带的弧后区域，其未解变形对理解当今北美-欧亚板块的相互作用至关重要。堪察加-阿留申交界处的演化是太平洋-欧亚板块边界的新生代演化的重要组成部分，因此也是整个北极构造的重要组成部分。该项目的主要目标是表征阿留申-堪察加交界处附近岩石圈和软流圈的温度和结构。温度与地震速度异常有关，变形结构与地震各向异性有关。温度和结构将揭示上地幔在板块间相互作用中的作用，特别是1)地幔过程如何促进阿留申-堪察加交界处附近活跃的俯冲相关火山活动，以及2)鄂霍次克海过去的伸展构造是否以及如何影响了北美洲-欧亚大陆边界的新生代发展。1998年至1999年，耶鲁大学首席研究员通过操作便携式宽带地震仪网络，在堪察加半岛获得了地震数据。该网络的记录与永久地震台站的数据将作为本研究的主要数据集。他们带来了区域构造、接收函数分析和利用地震各向异性表征岩石圈动力学的专业知识。科罗拉多首席研究员是地壳和上地幔模型的表面波层析成像反演以及从地震模型推断地幔温度的专家。该合作旨在生成堪察加-阿留申角附近各向同性和各向异性地震特征的准确和更清晰的图像。从这些图像中可以推断出限制岩石圈动力学的上地幔的温度和结构。

0136191ParkThis is a collaborative proposal between Principal Investigators at the University of Colorado and Yale University. Arctic tectonics is dominated by the interaction of the North American, Eurasian,and Pacific plates. In oceanic areas, the boundaries between these plates are relatively well known, but much of the North American-Eurasian plate boundary is defined by a broad zone of intra-continental deformation. The driving mechanisms for this deformation are poorly understood.Newly acquired seismic data makes it possible to decipher plate motion at the Aleutian-Kamchatka junction. This junction connects the strike-slip Bering fault along the western Aleutians with an active subduction zone beneath southern Kamchatka, where plate convergence is accompanied by vigorous arc-volcanics. The Okhotsk Sea lies in the back-arc region of the Kamchatka subduction zone, and its unresolved deformation is critical to understanding present-day North America-Eurasia plate interaction. The evolution of the Kamchatka-Aleutian junction is a critical component of the Cenozoic evolution of the Pacific-Eurasian plate boundary, and thus of Arctic tectonics as a whole. The principal goal of this project to characterize the temperature and the texture of the lithosphere and the asthenosphere near the Aleutian-Kamchatka junction region. Temperature is related to seismic velocity anomalies, and deformation texture to seismic anisotropy. Temperature and texture will reveal the role of the upper mantle in the interplay between the plates, particularly 1) how mantle processes facilitate the vigorous subduction-related volcanism near the Aleutian-Kamchatka junction, and 2) whether and how past extensional tectonics in the Okhotsk Sea have influenced the Cenozoic development of the North America-Eurasia boundary. The Yale Principal Investigators acquired seismic data in Kamchatka by operating a portable network of broadband seismometers in 1998 -1999. Recordings from this network combined with data from permanent seismological stations will for the primary data set for this study. They bring expertise in regional tectonics, receiver function analysis, and characterizing lithospheric dynamics using seismic anisotropy. The Colorado Principal Investigators are experts in surface wave tomography inversion for models of the crust and the upper mantle and the inference of mantle temperature from seismic models. This collaboration is designed to generate accurate and more sharply focused images of isotropic and anisotropic seismic features near the Kamchatka-Aleutian corner. From these images the temperature and texture of the upper mantle that constrains lithospheric dynamics will be inferred.