Long‐term tilt and acceleration data from the Logatchev Hydrothermal Vent Field, Mid‐Atlantic Ridge, measured by the Bremen Ocean Bottom Tiltmeter

Abstract

[1] Long-term seafloor deformations in the Logatchev Hydrothermal Vent Field (LHF) at the Mid-Atlantic Ridge are largely unexplored and unknown, even though the LHF has been the focus of international research for many years. As seafloor tilt and vertical acceleration provide key information about seafloor deformations, the Bremen Ocean Bottom Tiltmeter (OBT) was deployed in May 2005 at position 14°45 0 11.7 00 N, 44°58 0 47.0 00 W, 3035 m water depth in the LHF. The OBT recorded 384 days and was recovered in January 2007. Strong tilt steps and strong gradual tilt changes over less than a minute to days in the range of some 10 mrad and aligned mostly with the topography possibly indicate nearby mass movements like avalanches of bulk material due to local uplift or subsidence or may show tectonic activity. A vertically aligned high-resolution microelectromechanical systems (MEMS) accelerometer of type Servo K-Beam in the sensor package seems to be helpful to distinguish between tilt signals caused by a true rotation and fake tilt related to a transient translational motion of the OBT in a horizontal direction. Hodographs show elliptic motion patterns with about 1 mrad total tilt amplitude and distinct orientations of tilt toward hydrothermal vents. It is up to speculation whether the latter signals are related to hydrothermal fluid circulation. The amplitude spectra of these tilt signals and acceleration show discrete lines mostly between 0.1 and 50 mHz. The spectra show the periodic character of those signals and also proof that tides or bottom currents, which are known to show lower signal frequencies, or tremor, which generally has higher frequencies, are most likely not the reason. Compared with studies onshore and offshore, the LHF is most likely an area of strong and highly variable seafloor deformations.

Bottom pressure signals at the TAG deep‐sea hydrothermal field: Evidence for short‐period, flow‐induced ground deformation

“…Tilt cycles with similar periods have been observed near the Logatchev hydrothermal field on the MAR at 14°45 0 N [Fabian and Villinger, 2008], and when combined with our bottom pressure data, these observations provide compelling evidence for regular, hydrothermal flow-induced, GSD cycles at deep-sea hydrothermal fields.…”

Deciphering the ocean bottom pressure variation in the Logatchev hydrothermal field at the eastern flank of the Mid-Atlantic Ridge

“…These might reflect internal wave activity. In contrast to the observations of Fabian and Villinger [2008] and of Sohn et al…”

Geological context and vents morphology of the ultramafic‐hosted Ashadze hydrothermal areas (Mid‐Atlantic Ridge 13°N)

“…Pressure probe data for the TAG hydrothermal field shows periodic ground deformation that have been interpreted with a geyser‐like mechanism [ Sohn et al , 2009], yet TAG presents no craters. Tilt cycles with similar periods as those described at TAG by Sohn et al [2009] have been measured at the Logatchev field [ Fabian and Villinger , 2008]. These authors suggested that pressure fluctuations occur in the hydrothermal upflow zone with a periodicity comparable to those measured near on‐land geysers [ Nishimura et al , 2006].…”