Geowissenschaftliches Kolloquium

Mittwoch, 17. November 2021 - 12:15 Uhr
nur Online:

Dr. Pritam Yogeshwar (University of Cologne)

Boat-Towed Transient Electromagnetics - Investigation of the Furnas Volcanic Lake Hydrothermal System, Azores

Water-covered areas may lead to gaps in surface electromagnetic surveys, causing reduced resolution and, as a consequence, increased uncertainty in derived subsurface models. Boat-towed floating central loop time-domain electromagnetic techniques can mitigate this problem. Our proposed system 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. The field survey was performed on the Lagoa das Furnas (São 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.

Geowissenschaftliches Kolloquium "Perspectives of non-seismic applied near-surface geophysics"