scholarly journals Estimation of surficial sediment thickness using mid-frequency ocean acoustic bottom reflected signals measured in shallow water off Geoje island

2016 ◽  
Vol 35 (6) ◽  
pp. 419-426
Author(s):  
Hyuckjong Kwon ◽  
Jee Woong Choi ◽  
Su-Uk Son ◽  
Sungho Cho ◽  
Jooyoung Hahn ◽  
...  
Keyword(s):  
Shallow Water ◽  
Surficial Sediment ◽  
Sediment Thickness

scholarly journals Inversion of surficial sediment thickness from under-ice acoustic transmission measurement

2021 ◽  
Vol 149 (1) ◽  
pp. 371-385
Author(s):  
Nicholas P. Chotiros ◽  
Gaute Hope ◽  
Espen Storheim ◽  
Halvor Hobaek ◽  
Lee Freitag ◽  
...  
Keyword(s):  
Surficial Sediment ◽  
Transmission Measurement ◽  
Acoustic Transmission ◽  
Sediment Thickness

Deformation, earthquakes and tsunamis along thickly sedimented subduction: Arakan segment of the Sunda Arc

2021 ◽  
Author(s):  
Cecilia McHugh ◽  
Leonardo Seeber ◽  
Michael Steckler ◽  
Syed Humayun Akhter ◽  
Nickolas Dubin
Keyword(s):  
Shallow Water ◽  
Accretionary Prism ◽  
Live Coral ◽  
Sediment Thickness ◽  
Marine Terraces ◽  
Sunda Arc ◽  
Seismic Surveying ◽  
Splay Faults ◽  
Anelastic Deformation ◽  
Subbottom Profiling

<p>Incoming sediment thickness and composition are primary factors in the morphology and shallow structure of subduction boundaries. Sediment thickness in the Indian Ocean increases SE to NW along the Sunda arc. From <1km along Java to >15km where the boundary encounters the Ganges-Brahmaputra Delta (GBD). Here the accretionary prism broadens to the NW to >300 km wide. It is dominated by shallow-water to non-marine sediment. This segment also features a broad shallow megathrust overlain by linear anticlines rooted in splay faults. It is entirely above sea level and blind in its frontal part. This GBD segment transitions to a more familiar subduction structure and morphology along the submerged Arakan segment to the SE. The SE portion of this segment is characterized by larger splay faults that expose deep-water sediment with mud diapirism forming volcanoes and circular synclines. With increasing sediment input, the NW portion of the Arakan segment encroaches onto the GBD shelf. Both the SE and NW portions of the Arakan segment ruptured in the Mw>8.5 1762 tsunamigenic earthquake according to field and modeling evidence.</p><p>Uplifted coral reefs and marine terraces along the Myanmar and Bangladesh coasts document a >500 km rupture in 1762. The uplift, ranging from 6 m to 2 m from south to north, has been linked to rupture on the megathrust and on shallow splays. Tsunami deposits are traced for ~10 km along the St. Martin’s Island anticline and for >40 km along the Teknaf peninsula. Microfossils and mollusk assemblages in these deposits are consistently of shallow water affinity and date the tsunami to 1762. This deposit covers only a small fraction of the inferred megathrust rupture. If it is representative of the total tsunami distribution, a local anticline may have been the main source. Evidence from live coral microatolls show uplift on St. Martin’s Island continuing 250 years after the earthquake. This motion could stem from continued anelastic deformation of the anticline updip of the rupture. More widely distributed evidence from sediment and corals could address questions about megathrust and splay behavior in 1762 and after. Plans include multichannel seismic surveying, high resolution subbottom profiling and 40 m long piston coring to compare the SE to NW shelf portions to the Arakan segment along the Myanmar and Bangladesh coasts. More generally, we aim to better understand subduction and geohazards along thickly sedimented systems.</p>

Spatial assemblage structure of shallow-water reef fish in Southwest Australia

2020 ◽  
Vol 649 ◽  
pp. 125-140
Author(s):  
DS Goldsworthy ◽  
BJ Saunders ◽  
JRC Parker ◽  
ES Harvey
Keyword(s):  
Shallow Water ◽  
Reef Fish ◽  
Marine Environment ◽  
Fish Assemblages ◽  
Canopy Cover ◽  
Reef Fishes ◽  
Reef Fish Assemblage ◽  
Reef Type ◽  
Present Distribution ◽  
Southwest Australia

Bioregional categorisation of the Australian marine environment is essential to conserve and manage entire ecosystems, including the biota and associated habitats. It is important that these regions are optimally positioned to effectively plan for the protection of distinct assemblages. Recent climatic variation and changes to the marine environment in Southwest Australia (SWA) have resulted in shifts in species ranges and changes to the composition of marine assemblages. The goal of this study was to determine if the current bioregionalisation of SWA accurately represents the present distribution of shallow-water reef fishes across 2000 km of its subtropical and temperate coastline. Data was collected in 2015 using diver-operated underwater stereo-video surveys from 7 regions between Port Gregory (north of Geraldton) to the east of Esperance. This study indicated that (1) the shallow-water reef fish of SWA formed 4 distinct assemblages along the coast: one Midwestern, one Central and 2 Southern Assemblages; (2) differences between these fish assemblages were primarily driven by sea surface temperature, Ecklonia radiata cover, non-E. radiata (canopy) cover, understorey algae cover, reef type and reef height; and (3) each of the 4 assemblages were characterised by a high number of short-range Australian and Western Australian endemic species. The findings from this study suggest that 4, rather than the existing 3 bioregions would more effectively capture the shallow-water reef fish assemblage patterns, with boundaries having shifted southwards likely associated with ocean warming.

Low mode acoustics of shallow water waveguides

2011 ◽  
Vol 181 (11) ◽  
pp. 1222 ◽  
Author(s):  
Aleksandr G. Luchinin ◽  
Aleksandr I. Khil'ko
Keyword(s):  
Shallow Water
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