Nonseismic Signals in the Ocean: Indicators of Deep Sea and Seafloor Processes on Ocean‐Bottom Seismometer Data

Autor: Jing Yi Lin, Clément Monteil, Gaye Bayrakci, David Dellong, Emmy T. Y. Chang, Eve Tsang-Hin-Sun, Louis Géli, Frauke Klingelhoefer, Evangelia Batsi
Přispěvatelé: Laboratoire Géosciences Océan (LGO), Université de Bretagne Sud (UBS)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), University of Southampton, National Chiao Tung University (NCTU), National Central University [Taiwan] (NCU), European Commission, EC: 116Y371, ANR‐16‐CE03‐0010‐02Seventh Framework Programme, FP7, Institut Français de Recherche pour l'Exploitation de la Mer - Brest (IFREMER Centre de Bretagne), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)
Rok vydání: 2019
Předmět:
Zdroj: Geochemistry, Geophysics, Geosystems
Geochemistry, Geophysics, Geosystems, AGU and the Geochemical Society, 2019, 20 (8), pp.3882-3900. ⟨10.1029/2019GC008349⟩
Geochemistry Geophysics Geosystems (1525-2027) (American Geophysical Union (AGU)), 2019-08, Vol. 20, N. 8, P. 3882-3900
ISSN: 1525-2027
Popis: Ocean bottom seismometers (OBS) commonly record short duration events (SDEs), that could be described by all of these characteristics: (i) duration < 1 s, (ii) one single‐wave train with no identified P‐ nor S‐wave arrivals and (iii) a dominant frequency usually between 4 Hz and 30 Hz. In many areas, SDEs have been associated with gas or fluid‐related processes near cold seeps or hydrothermal vents, although fish bumps, instrumental or current‐generated noise have been proposed as possible sources. In order to address some remaining issues, this study presents results from in situ and laboratory experiments combined with observations from 2 contrasting areas, the Sea of Marmara (Turkey) and the Chilean subduction zone. The in situ experiment was conducted at the EMSO‐Molène submarine observatory (near Brest, France) and consisted in continuously monitoring two OBSs with a camera. The images revealed that no fish regularly bumped into the instruments. Laboratory experiments aimed at reproducing SDEs’ waveforms by injecting air or water in a tank filled by sand and sea‐water and monitored with an OBS. Injecting air in the sediments produced waveforms very similar to the observed SDEs, while injecting air in the water column did not, constraining the source of SDEs in the seafloor sediments. Finally, the systematic analysis of two real data sets revealed that it is possible to discriminate gas‐related SDEs from biological or sea‐state related noise from simple source parameters, such as the temporal mode of occurrence, the back azimuth and the dominant frequency. Key Points Short duration high amplitude events routinely recorded on marine seismometers are not created by fish bumping into the geophone. In laboratory experiments, the waveforms of these events are well reproduced by fluid migration in the sediments. We propose 3 simple source parameters to discriminate gas‐related short duration events in ocean bottom seismometer data.
Databáze: OpenAIRE