Print Email Facebook Twitter Passive Deep Ocean Thermometry using Hydroacoustic Signals from Submarine Earthquakes Title Passive Deep Ocean Thermometry using Hydroacoustic Signals from Submarine Earthquakes Author Morandini, Ludovic (TU Delft Civil Engineering & Geosciences; TU Delft Applied Geophysics and Petrophysics) Contributor Shani-Kadmiel, Shahar (mentor) Evers, L.G. (graduation committee) Ghose, R. (graduation committee) Wagner, Florian (graduation committee) Degree granting institution Delft University of Technology Programme Applied Geophysics | IDEA League Date 2020-08-21 Abstract Measuring temperature variations of the deep ocean is necessary to evaluate the heat flux between the atmosphere and the hydrosphere and thus calibrate climate change models. In the last two decades a passive alternative to profiling oceanographic floats has emerged: hydroacoustic thermometry. This method consists of using the oceanic ambient noise field as a source of acoustic waves and hydrophone arrays as receivers. These sensors are part of the International Monitoring System which is in place for the verification of the Comprehensive Nuclear-Test-Ban Treaty. They are positioned at a water depth of approximately 1 km, in the Sound Fixing and Ranging channel. This channel is a low-velocity layer that functions as an acoustic wave guide, thus facilitating very long range propagation with little attenuation. This study analyses transient signals between 2005 and 2018 triggered by submarine earthquakes and detected at station H10, situated near Ascension Island in the South Atlantic Ocean. This station consists of two three-element (triplet) arrays with an aperture of approximately 2 km each. The triplets are 126 km apart. Array processing techniques applied to individual triplets are prone to be biased by local conditions of the array surroundings. We demonstrate that this bias is largely suppressed when jointly processing both triplets as one six-elements array. Due to the malfunction of element S1, data quality decreased after October 2013 and our results are less robust. For the 2005-2013 period, we retrieve a temperature of 4.3 to 4.8 °C. Subject GeophysicsThermometryBeamformingHydroacousticSignalsOceanEarthquakes To reference this document use: http://resolver.tudelft.nl/uuid:746ad403-689e-4a07-9da4-5523ddc93e09 Part of collection Student theses Document type master thesis Rights © 2020 Ludovic Morandini Files PDF Morandini_Thesis.pdf 16.38 MB Close viewer /islandora/object/uuid:746ad403-689e-4a07-9da4-5523ddc93e09/datastream/OBJ/view