Source Complications in EarthScope Magnetotelluric Data: Challenges and Opportunities
The EarthScope USArray project has collected long period MT data which can be analyzed as a series of overlapping synoptic 2D arrays with moderately wide (several hundred km) aperture in both N-S and E-W directions. These data thus provide an excellent opportunity to explore non-uniform sources, and their impact on traditional geomagnetic transfer functions. The configuration of sites in some arrays is also well suited to exploring new approaches to generalized horizontal spatial gradient (HSG) methods. Here we apply multivariate statistical methods that we have previously developed to explore the spatial structure of sources, and to test methods for simultaneous estimation of plane wave and gradient responses. We show that there are very significant source gradient biases in the simplest inter-site TF estimates, including large effects on Hx TFs in narrow bands associated with PC activity, and broadband biases in Hy TFs, which we hypothesize result from the dominance of field aligned currents in the E-W magnetic components. Stable estimates of a three component gradient HSG estimates are obtained for periods of 10-103 s.These additional TFs, which are presumably less impacted by local near surface distortion, might ultimately be used to reduce ambiguity in interpretation of widely spaced MT data.
Magnetotellurics Array Processing EM Sources Transfer Functions EarthScope
Gary D Egbert
College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, OR, USA
国际会议
The 19th International Workshop on Electromagnetic Induction in the Earth(第十九届国际地球电磁感应学术研讨会)
北京
英文
948-953
2008-10-23（万方平台首次上网日期，不代表论文的发表时间）