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| Registros recuperados: 12 | |
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| Tiberi, C.; Gautier, S; Ebinger, C.; Roecker, S.; Plasman, M.; Albaric, J.; Deverchere, Jacques; Peyrat, S.; Perrot, Julie; Wambura, R. Ferdinand; Msabi, M.; Muzuka, A.; Mulibo, G.; Kianji, G.. |
| We present a joint analysis of newly acquired gravity and teleseismic data in the North Tanzanian Divergence, where the lithospheric break-up is at its earliest stage. The impact of a mantle upwelling in more mature branches of the East African Rift has been extensively studied at a lithospheric scale. However, few studies have been completed that relate the deep-seated mantle anomaly detected in broad regional seismic tomography with the surface deformation observed in the thick Archaean Pan-African suture zone located in North Tanzania. Our joint inversion closes the gap between local and regional geophysical studies, providing velocity and density structures from the surface down to ca. 250 km depth with new details. Our results support the idea of a... |
| Tipo: Text |
Palavras-chave: Gravity anomalies and Earth structure; Africa; Joint inversion; Seismic tomography; Intra-plate processes. |
| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00637/74944/76038.pdf |
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| Bayrakci, Gaye; Laigle, Mireille; Becel, A.; Hirn, A.; Taymaz, T.; Yolsal-cevikbilen, S.. |
| A 3-D tomographic inversion of first arrival times of shot profiles recorded by a dense 2-D OBS network provides an unprecedented constraint on the P-wave velocities heterogeneity of the upper-crustal part of the North Marmara Trough (NMT), over a region of 180 km long by 50 km wide. One of the specific aims of this controlled source tomography is to provide a 3-D initial model for the local earthquake tomography (LET). Hence, in an original way, the controlled source inversion has been performed by using a code dedicated to LET. After several tests to check the results trade-off with the inversion parameters, we build up a 3-D a priori velocity model, in which the sea-bottom topography, the acoustic and the crystalline basements and the Moho interfaces... |
| Tipo: Text |
Palavras-chave: Body waves; Seismic tomography; Continental tectonics: strike-slip and transform; Crustal structure.. |
| Ano: 2013 |
URL: http://archimer.ifremer.fr/doc/00185/29601/28033.pdf |
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| Hable, Sarah; Sigloch, Karin; Stutzmann, Eleonore; Kiselev, Sergey; Barruol, Guilhem. |
| We use seismic noise cross-correlations to obtain a 3-D tomography model of SV-wave velocities beneath the western Indian Ocean, in the depth range of the oceanic crust and uppermost mantle. The study area covers 2000×2000 km2 between Madagascar and the three spreading ridges of the Indian Ocean, centred on the volcanic hotspot of La Réunion. We use seismograms from 38 ocean bottom seismometers (OBSs) deployed by the RHUM-RUM project and 10 island stations on La Réunion, Madagascar, Mauritius, Rodrigues, and Tromelin. Phase cross-correlations are calculated for 1119 OBS-to-OBS, land-to-OBS, and land-to-land station pairs, and a phase-weighted stacking algorithm yields robust group velocity measurements in the period range of 3-50 s. We demonstrate that OBS... |
| Tipo: Text |
Palavras-chave: Crustal imaging; Seismic instruments; Seismic interferometry; Seismic noise; Seismic tomography. |
| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00508/61988/66099.pdf |
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| Lin, Jing-yi; Hsu, Sk; Sibuet, Jean-claude. |
| [1] Behind the sedimentary Ryukyu arc lies the Okinawa Trough, whose termination is located at the tip of the Ilan plain ( northern Taiwan), just above the Ryukyu slab edge. The present-day active volcanic front is located 80 - 100 km above the Ryukyu slab and extends from Japan to Kueishantao Island, an islet situated 10 km offshore the Ilan plain. Between December 1990 and May 1999, 3370 earthquakes recorded in northern Taiwan by 65 seismic land stations were used to determine the three-dimensional V-p and V-s velocity structures and V-p/V-s ratios. A low V-s but high V-p/V-s sausage-like body, similar to 30 km in diameter, lies within the Eurasian mantle wedge, on top of the western Ryukyu slab extremity, at depths ranging between 20 and 100 km. We... |
| Tipo: Text |
Palavras-chave: Ryukyu slab; Okinawa Trough; Seismic tomography; Melting features. |
| Ano: 2004 |
URL: https://archimer.ifremer.fr/doc/00000/10898/7751.pdf |
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| Chauhan, Ajay P. S.; Singh, Satish C.; Hananto, Nugroho D.; Carton, Helene; Klingelhoefer, Frauke; Dessa, J. -x.; Permana, H.; White, N. J.; Graindorge, D.. |
| Forearc tectonics at accretionary convergent margins has variously been studied using analogue and numerical modelling techniques. Numerous geophysical investigations have targeted the subsurface structure of active forearc settings at convergent margins. However, several critical details of the structure, mode of tectonic evolution and the role forearcs play in the subduction seismic cycle remain to be further understood, especially for large accretionary margins. In this study, we present a high-resolution deep seismic reflection image of the northern Sumatran subduction forearc, near the 2004 December 26 Sumatra earthquake epicentral region. The profile clearly demarcates the backthrust branches at the seaward edge of the Aceh forearc basin, along which... |
| Tipo: Text |
Palavras-chave: Forearc backthrusting; Seismic reflection image; Seismic tomography; Subduction zone processes. |
| Ano: 2009 |
URL: https://archimer.ifremer.fr/doc/00000/11120/7720.pdf |
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| Klingelhoefer, Frauke; Evain, Mikael; Afilhado, A.; Rigoti, Caesar; Loureiro, Afonso; Alves, D.; Lepretre, Angelique; Moulin, Maryline; Schnurle, Philippe; Benabdellouahed, Massinissa; Baltzer, Agnes; Rabineau, Marina; Feld, Aurelie; Viana, A.; Aslanian, Daniel. |
| During the Sanba (Santos basin seismic transect) experiment in 2010–2011, a 380-km-long combined wide-angle and reflection seismic profile has been acquired using 30 ocean-bottom seismometers, a 4.5 km seismic streamer and a 8900 in.3 airgun array. The Sanba 3 profile crosses the southern flank of the Sao Paulo Plateau, the Sao Paulo Ridge and the easternmost Santos Basin in an east–west direction. Its eastern end is located on undisturbed oceanic crust. Tomographic and forward modelling of the wide-angle seismic data reveals that the sedimentary thickness is variable with only 1–2 km on top of the ridge and thickening to 4–5 km in the basin. Crustal thickness at the ridge is about 18 km and the relative layer thickness and velocity gradients indicate a... |
| Tipo: Text |
Palavras-chave: Controlled source seismology; Seismic tomography; Mid-ocean ridge processes; Continental margins: divergent; Continental tectonics: extensional; Crustal structure; South America. |
| Ano: 2015 |
URL: http://archimer.ifremer.fr/doc/00242/35296/33826.pdf |
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| Badji, Rabia; Charvis, Philippe; Bracene, Rabah; Galve, Audrey; Badsi, Madjid; Ribodetti, Alessandra; Benaissa, Zahia; Klingelhoefer, Frauke; Medaouri, Mourad; Beslier, Marie-odile. |
| For the first time, a deep seismic data set acquired in the frame of the Algerian-French SPIRAL program provides new insights regarding the origin of the westernmost Algerian margin and basin. We performed a tomographic inversion of traveltimes along a 100-km-long wide-angle seismic profile shot over 40 ocean bottom seismometers offshore Mostaganem (Northwestern Algeria). The resulting velocity model and multichannel seismic reflection profiles show a thin (3-4 km thick) oceanic crust. The narrow ocean-continent transition (less than 10 km wide) is bounded by vertical faults and surmounted by a narrow almost continuous basin filled with Miocene to Quaternary sediments. This fault system, as well as the faults organized in a negative-flower structure on the... |
| Tipo: Text |
Palavras-chave: Seismic tomography; Continental margins: transform; Crustal structure; Africa; Europe.. |
| Ano: 2015 |
URL: http://archimer.ifremer.fr/doc/00255/36670/35278.pdf |
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| Auger, E; Virieux, J; Zollo, A. |
| In this paper, we show how the migration of active seismic data can be used to identify and position a seismic discontinuity in a complex medium, and how the amplitude variations of the converted P to S waves can be interpreted to constrain the seismic velocities below the interface. For the application we turn our attention on Mt Vesuvius, an active volcano threatening a densely populated area. To better define its plumbing system, we investigate a mid-crust seismic discontinuity first identified by Zollo et al. (1996, Science, 274, 592-594) and assumed to be the top of a layer containing low-velocity material. We deduce a reference velocity model from previous works on first arrival times, and use it to migrate PP reflected and PS converted waves. In the... |
| Tipo: Text |
Palavras-chave: Crustal structure; Explosion seismology; Low-velocity layer; S waves; Seismic tomography; Volcanic structure. |
| Ano: 2003 |
URL: https://archimer.ifremer.fr/doc/00466/57760/60035.pdf |
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| Adimah, N I; Padhy, S. |
| The unusual complex lithospheric structure of Madagascar is a product of a number of important geological events, including: the Pan-African Orogeny, episodes of Late Cenozoic intraplate volcanism and several phases of deformation and metamorphism. Despite this rich history, its detailed crustal structure remains largely underexplored. Here, we take advantage of the recently obtained data set of the RHUM-RUM (Réunion Hotspot and Upper Mantle–Réunions Unterer Mantel) seismological experiment, in addition to previously available data sets to generate the first Rayleigh wave group velocity maps across the entire island at periods between 5 and 30 s using the ambient noise tomography technique. Prior to preliminary data preparation, data from Ocean Bottom... |
| Tipo: Text |
Palavras-chave: Seismic tomography; Africa; Crustal structure; Surface waves and free oscillations; Seismic noise.. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00600/71184/69539.pdf |
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| Huang, Haibo; Qiu, Xuelin; Pichot, Thibaud; Klingelhoefer, Frauke; Zhao, Minghui; Wang, Ping; Hao, Tianyao. |
| Evolution of the continental margins of the South China Sea (SCS) is one of the open questions when discussing continental breakup and seafloor spreading. We processed data from a wide-angle seismic profile (OBS2011–1), which passes through the northwestern margin of the SCS, and performed travel time modeling to obtain the seismic velocity structures. The modeling results show a stepwise variation of the crustal thicknesses from continental margin to oceanic basin. Stretching factor of the upper crust is nearly double the estimate of the lower crust along the Zhongsha Trough. The lower crust shows asymmetrical upwelling towards the trough center, accompanied by ∼0.3 km/s of the velocity increase due to magmatic addition. The upper and lower crusts have... |
| Tipo: Text |
Palavras-chave: Seismic tomography; Continental tectonics: extensional; Crustal structure; Rheology: crust and lithosphere. |
| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00500/61189/64720.pdf |
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| Ghosal, Dibakar; Singh, S. C.; Martin, J.. |
| In subduction zones, shallow subsurface structures are the manifestation of the plate interactions at depth. However, significant water depths, rough bathymetry and presence of heavily deformed accretionary wedge materials hamper imaging of the near-surface features to a great extent using conventional imaging techniques. In this study, we show results using an integrated processing technique to a multichannel seismic data set acquired in 2006 from the northwestern offshore Sumatra. We start with first downward continuing the 12-km-long surface streamer data to the seafloor, followed by a high-resolution traveltime tomography of refracted phases to determine a detailed velocity-depth model of subsurface, which in turns, is used for pre-stack depth... |
| Tipo: Text |
Palavras-chave: Controlled source seismology; Seismic tomography; Subduction zone processes; Continental margins: convergent; Folds and folding. |
| Ano: 2014 |
URL: https://archimer.ifremer.fr/doc/00290/40094/39185.pdf |
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| Registros recuperados: 12 | |
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