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| Collot, Julien; Lewis, Keith; Lamarche, Geoffroy; Lallemand, Serge. |
| Despite convergent margins being unstable systems, most reports of huge submarine slope failure have come from oceanic volcanoes and passive margins. Swath bathymetry and seismic profiles of the northern Hikurangi subduction system, New Zealand, show a tapering 65–30 km wide by 65 km deep margin indentation, with a giant, 3150±630 km3, blocky, debris avalanche deposit projecting 40 km out across horizontal trench fill, and a debris flow deposit projecting over 100 km. Slide blocks are well‐bedded, up to 18 km across and 1.2 km high, the largest being at the avalanche deposit's leading edge. Samples dredged from them are mainly Miocene shelf calc‐mudstones similar to those outcropping around the indentation. Cores from cover beds suggest that failure... |
| Tipo: Text |
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| Ano: 2001 |
URL: https://archimer.ifremer.fr/doc/00683/79509/82127.pdf |
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| Lamarche, Geoffroy; Lurton, Xavier. |
| Multibeam echosounders are becoming widespread for the purposes of seafloor bathymetry mapping, but the acquisition and the use of seafloor backscatter measurements, acquired simultaneously with the bathymetric data, are still insufficiently understood, controlled and standardized. This presents an obstacle to well-accepted, standardized analysis and application by end users. The Marine Geological and Biological Habitat Mapping group (Geohab.org) has long recognized the need for better coherence and common agreement on acquisition, processing and interpretation of seafloor backscatter data, and established the Backscatter Working Group (BSWG) in May 2013. This paper presents an overview of this initiative, the mandate, structure and program of the working... |
| Tipo: Text |
Palavras-chave: Multibeam echosounders; Calibration; Reflectivity; Mapping; Seafloor. |
| Ano: 2018 |
URL: http://archimer.ifremer.fr/doc/00385/49655/50179.pdf |
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| Proust, Jean-noel; Lamarche, Geoffroy; Migeon, Sébastien; Neil, Helen. |
| Many countries have recognized climate change due to human activities as one of the most critical issues facing the modern world. However, validating predictive models of the potential anthropogenic impact on shaping the Earth's surface requires the examination and documentation of analogous tectonic and climate changes of the past, working with the paradigm that past environmental changes are keys to understanding the future. A France-New Zealand research program, which also involves institutions from several other countries, aims to disentangle the impact of tectonics and climate on the landscape evolution of New Zealand over the past million years, at a very high resolution timescale—with steps as small as 100 years, i.e., relating to events such as... |
| Tipo: Text |
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| Ano: 2008 |
URL: http://archimer.ifremer.fr/doc/00248/35892/34428.pdf |
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| Lamarche, Geoffroy; Joanne, Cathy; Collot, Jean-yves. |
| Four > 100 km(3) mass-transport deposits (MTDs) identified from their morphology and seismic facies across the Matakaoa Margin and Raukumara fore-arc basin, NE New Zealand, constitute the Matakaoa Submarine Instability Complex (MSIC). MSIC originates from a 45-km-wide, 1100-m-high reentrant in the continental slope. The deposits resulted from three mass-failure events: ( 1) The Raukumara Slump is identified from the collapsed NW flank of an anticline at the northern end of the reentrant and imbricate structures at its distal end, overlying a flat decollement over a > 50-km distance. The slump age is roughly estimated between upper Miocene and lower Pleistocene. (2) The Matakaoa Debris Avalanche (MDA) is subdivided into a similar to 260-km(3) blocky... |
| Tipo: Text |
Palavras-chave: Submarine landslide; Debris flow; Slump; Debris avalanche; Raukumara Basin; Hikurangi Margin. |
| Ano: 2008 |
URL: https://archimer.ifremer.fr/doc/00237/34861/33203.pdf |
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| Lamarche, Geoffroy; Lurton, Xavier; Verdier, Anne-laure; Augustin, Jean-marie. |
| A comprehensive EM300 multibeam echo-sounder dataset acquired from Cook Strait, New Zealand, is used to develop a regional-scale objective characterisation of the seafloor. Sediment samples and high-resolution seismic data are used for ground-truthing. SonarScope (R) software is used to process the data, including signal corrections from sensor bias, specular reflection compensation and speckle noise filtering aiming at attenuating the effects of recording equipment, seafloor topography, and water column. The processing is completed by correlating a quantitative description (the Generic Seafloor Acoustic Backscatter-GSAB model) with the backscatter data. The calibrated Backscattering Strength (BS) is used to provide information on the physical... |
| Tipo: Text |
Palavras-chave: Backscatter; Multibeam echo-sounder; Sediment waves; Habitat mapping. |
| Ano: 2011 |
URL: http://archimer.ifremer.fr/doc/00031/14260/11552.pdf |
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| Nodder, Scott D.; Lamarche, Geoffroy; Proust, Jean-noel; Stirling, Mark. |
| [1] Seafloor fault scarps and near-surface deformation of late Quaternary seismic reflectors occur along the eastern margin of the Wanganui Basin, 200 km behind the active Hikurangi subduction front, southern North Island, New Zealand. The offshore scarps are associated with the low-strain, compressional Kapiti-Manawatu Fault System (KMFS), which comprises high-angle (> 60 degrees) reactivated reverse and normal faults oriented NE-SW, highly oblique to the coast. Seafloor scarps range from < 10 to 50 km in length with vertical seafloor offsets of 2 to 30 m. The longest structure is the Mascarin Fault, with maximum late Quaternary vertical slip rates of 3 mm a(-1) (where a is years). Other faults in the KMFS have typical rates of < 1 mm a(-1),... |
| Tipo: Text |
Palavras-chave: Hikurangi subduction zone; Active normal fault; Wanganui basin; Surface rupture; North island; Seismic hazard; Wellington region; Taranaki basin; Ohariu fault; Cook strait. |
| Ano: 2007 |
URL: https://archimer.ifremer.fr/doc/00207/31839/30253.pdf |
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