Magnetotelluric imaging of the Society Islands hotspot

Abstract

Abstract. In April-June 1989, seafloor magnetotelluric data across and along the leading edge of the Tahiti hotspot were obtained. The magnetotelluric response functions were found to be strongly influenced by bathymetric and island effects, and a new procedure for modeling and removing this distortion using a thin sheet approach combined with the measured water depths is introduced. The corrected response functions are consistent with a two-dimensional structure. Inversion of the data shows a slightly higher conductivity (relative to a reference site located away from the hotspot) down to 130 km depth beneath the active area southeast of Tahiti underlain by a more resistive structure. There is a suggestion for a change in conductivity in the 400-450 kln depth range, which is consistent with elevated temperatures. This result is consistent with a mantle plume of limited extent (less than 150 km radius) located near the leading edge of the Tahiti hotspot. The rnagnetotelluric data provide no evidence for lithospheric thinning or for a strong thermal influence over a large area, as would be required by a superswell model.

TIARES Project—Tomographic investigation by seafloor array experiment for the Society hotspot

“…1, modified from Suetsugu et al, 2009). The small-scale anomalies, possibly mantle plumes, are present beneath the Society and Macdonald hotspots, which agrees with the results obtained from early magnetotelluric tomography (Nolasco et al, 1998). However, the explanation remained unclear because the insufficient station coverage impeded the investigation of the anomaly routes to the hotspots and their depth extents.…”

Two-dimensional Inversion of Sea-effect-corrected Magnetotelluric (MT) Data in Jeju Island

“…일반적으로 심부지각 구조를 조사하기 위해서는, 자연송신원 자기지전류(MT; Magnetotelluric) 탐사가 폭넓게 활용된다 (Jones, 1999;Jones and Ferguson, 2001 (Nolasco et al, 1998;Santos et al, 2001;Yang et al, 2010 …”

A study on correction equations for the effect of seafloor topography on ocean bottom magnetotelluric data

“…The correction method is further classified into approaches with or without forward modeling. For the approach with forward modeling, the electromagnetic fields are modeled for a resistivity structure with and without topography to acquire distortion terms which are used for the correction (e.g., Nolasco et al, 1998). On the other hand, for the approach without forward modeling, tensor decomposition is frequently used because of its availability, esCopyright c The Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS); The Seismological Society of Japan; The Volcanological Society of Japan; The Geodetic Society of Japan; The Japanese Society for Planetary Sciences; TERRAPUB.…”

“…These differences are caused by differences in treatment of the distortions of magnetic field and in robustness of the correction equation to a resistivity structure assumed for the topographic correction. The results suggest that the correction equation of Nolasco et al (1998) should be used because it better accommodates the estimation of unknown resistivity structures. We apply the correction equation of Nolasco et al (1998) to a response observed in the Mariana area.…”

“…The results suggest that the correction equation of Nolasco et al (1998) should be used because it better accommodates the estimation of unknown resistivity structures. We apply the correction equation of Nolasco et al (1998) to a response observed in the Mariana area. The one-dimensional resistivity structure estimated from the corrected response explains almost all the components of the observed response.…”