关键词: 长周期大地电磁, 响应函数, 阻抗, 感应矢量, 倾子, 青藏高原

Abstract: As a complement to conventional MT,Long-period Magnetotellurics("LMT") has been developed at low frequency for soundings of deep electric structures.Due to the thick and low resistive crust and upper mantle in east Tibetan Plateau,the conventional MT could not provide sufficient information about deep structures of the study area that requested long period MT measurement to be complemented.This paper presents brief introduction of LMT in respect of the concept,data acquisition,processing,modeling,inversion and interpretation.Most important is that practical LMT sounding applied in eastern Tibetan Plateau gives the LMT transfer functions of impedance and tipper,which coincide with conventional MT.The result of the LMT profile illustrates the wide distribution of high-conductivity layers and provides more information about the base of the conductors beneath the eastern Tibetan Plateau,with higher resolution.Anomalous induction coefficients and 2-D model suggest extensive conductive bodies beneath Lhasa block and Qiangtang terrain which would be a possible evidence for partial melt and fluids at depth.

Key words: long-period magnetotellurics, transfer function, impedance, induction arrow, tipper, Tibetan Plateau