Universität zu Köln

Yogeshwar, Pritam, Kuepper, Mira, Tezkan, Buelent, Rath, Volker ORCID: 0000-0001-9558-6726, Kiyan, Duygu, Byrdina, Svetlana, Cruz, Jose ORCID: 0000-0002-6475-3824, Andrade, Cesar and Viveiros, Fatima (2020). Innovative boat-towed transient electromagnetics - Investigation of the Furnas volcanic lake hydrothermal system, Azores. Geophysics, 85 (2). S. E41 - 16. TULSA: SOC EXPLORATION GEOPHYSICISTS. ISSN 1942-2156

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Abstract

Water-covered areas may lead to gaps in surface electromagnetic surveys, causing reduced resolution and, as a consequence, increased uncertainty in derived subsurface models. We have evaluated a boat-towed floating central loop time-domain electromagnetic technique that mitigates this problem. It facilitates obtaining data with a spatial sampling density, which is rarely possible with standard instrumentation on land, and it only requires moderate logistical effort. A unique field study on a shallow volcanic lake demonstrated that this method is feasible with only a minor loss of accuracy when compared to anchored and land soundings. We found that the noise sources arising from the moving instrument and the boat engine can be neglected. The field survey was performed on the Lagoa das Furnas (Sao Miguel, Azores Islands, Portugal), which is located within an active volcanic area and is characterized by fumarolic fields and CO2 degassing. Thus, the associated hydrothermal system is expected to extend below the lake. However, the character, geometry, and extent of this system are unknown because of the lack of boreholes and geophysical studies. In total, 600 soundings, combining towed profiles with anchored and land-based soundings, were acquired with an aim of imaging the hydrothermal system beneath the lake down to 200 m. The results from all three types of measurements compare well and thus led to consistent 1D inversion models. The inversion results delineate a highly conductive, smectite-rich cap layer dipping below the lake away from the main fumarole zone. Near this zone, the extent of the conductor agrees well with an area of intense dispersed CO2 degassing, which appears to be controlled by at least two electrically distinctive fault zones in which the conductor is found at greater depths.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Yogeshwar, Pritam UNSPECIFIED UNSPECIFIED UNSPECIFIED Kuepper, Mira UNSPECIFIED UNSPECIFIED UNSPECIFIED Tezkan, Buelent UNSPECIFIED UNSPECIFIED UNSPECIFIED Rath, Volker UNSPECIFIED orcid.org/0000-0001-9558-6726 UNSPECIFIED Kiyan, Duygu UNSPECIFIED UNSPECIFIED UNSPECIFIED Byrdina, Svetlana UNSPECIFIED UNSPECIFIED UNSPECIFIED Cruz, Jose UNSPECIFIED orcid.org/0000-0002-6475-3824 UNSPECIFIED Andrade, Cesar UNSPECIFIED UNSPECIFIED UNSPECIFIED Viveiros, Fatima UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-342747
DOI:	10.1190/GEO2019-0292.1
Journal or Publication Title:	Geophysics
Volume:	85
Number:	2
Page Range:	S. E41 - 16
Date:	2020
Publisher:	SOC EXPLORATION GEOPHYSICISTS
Place of Publication:	TULSA
ISSN:	1942-2156
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language SAO-MIGUEL ISLAND; RESOLUTION; INVERSION; SOUNDINGS; SURFACE; TRENDS; DEPTH Multiple languages Geochemistry & Geophysics Multiple languages
URI:	http://kups.ub.uni-koeln.de/id/eprint/34274