Open AccessBeyond magnetotelluric decomposition: Induction, current channeling, and magnetotelluric phases over 90°
Author(s) -
Lezaeta Pamela,
Haak Volker
Publication year - 2003
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2001jb000990
Subject(s) - magnetotellurics , geology , electrical conductor , current (fluid) , geophysics , seismology , anisotropy , subduction , fault (geology) , crust , conductor , electrical resistivity and conductivity , tectonics , geometry , physics , oceanography , mathematics , quantum mechanics
This paper presents a method to examine strong current channeling affecting the magnetotelluric (MT) impedances, going beyond existing tensor decomposition schemes. The method allows recognition of elongated conductors in the crust and is also useful for a qualitative recognition of general three‐dimensional (3‐D) high‐conductivity anomalies. This has been tested with synthetic data from 3‐D and 2‐D anisotropic models. The current channeling analysis has been applied to MT data collected in the Andean subduction zone, where the Atacama megafault system close to the Pacific Ocean and oriented subparallel to the coast line is located. The analysis suggests the presence of vertical dike‐like conductors of limited lateral extent along the fault zone. Several MT sites distributed along the faults have impedance phases of the electric field tangential to the local azimuth far exceeding 90° at longer periods. We are able to explain this as being the result of strong current channeling producing magnetic distortion due to an electromagnetic coupling between the conductive ocean and the continental elongated conductors.