| Titre | Deformation of the northern Sumatra accretionary prism from high-resolution seismic reflection profiles and ROV observations |
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| Auteur | Mosher, D C ;
Austin, J A, Jr; Fisher, D; Gulick, S P S |
| Source | Marine Geology vol. 252, issue 3-4, 2008 p. 89-99, https://doi.org/10.1016/j.margeo.2008.03.014 |
| Liens | Supplementary Data - Données supplémentaires
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| Image |  |
| Année | 2008 |
| Séries alt. | Secteur des sciences de la Terre, Contribution externe 20070360 |
| Séries alt. | University of Texas, Institute for Geophysics, Contribution 1983 |
| Éditeur | Elsevier BV |
| Document | publication en série |
| Lang. | anglais |
| DOI | https://doi.org/10.1016/j.margeo.2008.03.014 |
| Media | papier; en ligne; numérique |
| Formats | html; pdf (Adobe® Reader®) |
| Région | Indian Ocean; northern Sumatra; Sunda Trench; Aceh Basin |
| Lat/Long OENS | 91.5000 95.2500 6.0000 3.0000 |
| Sujets | déformation; levés géophysiques; levés de reflexion sismiques; profils sismiques marins; tectonique de plaques; marges plaques; zones de subduction; cadre tectonique; éléments tectoniques; évolution
tectonique; interprétations tectoniques; déplacement; accretion; bathymétrie; analyses structurales; caractéristiques structurales; failles; failles normales; failles, décrochement; plis; diaclases; fractures; evolution du bassin; affaissement;
sédimentation; structures sédimentaires; plans de litage; éboulis; sédiments marins; mouvement de masse; secousses séismiques; sismicité; déformation; tsunami; photogéologie; photographie; Tremblement de terre de 2004 Great Sumatran-Andaman ; Zone de
faille de West Andaman ; Plaque Indienne-Australienne; Plaque d'Aceh ; Plaque de Burma ; géophysique; tectonique; géologie marine; géologie structurale |
| Illustrations | croquis cartographiques; modèles altimétriques numériques; profils de réflexion sismique; photographies; blocs-diagrammes |
| Programme | Les géosciences à l'appui de la gestion des océans Aléas géologiques et contraintes à la mise en valeur des ressources extracôtières |
| Diffusé | 2008 07 01 |
| Résumé | (disponible en anglais seulement)
Following the 2004 Great Sumatran-Andaman Mw ~9.2 earthquake, high-resolution seismic reflection, multibeam bathymetric and remotely operated vehicle data were
acquired to investigate the tectonic framework of the rupture zone and search for evidence of seafloor and near-surface displacement. Three distinct regions off northern Sumatra were investigated; 1) a portion of the Sunda Trench, 2) the
adjacent
frontal deformation zone, and 3) the seaward flank of the Aceh (forearc) Basin. A thick (N1.5 km) sediment section within the Sunda Trench shows evidence of shallow normal faulting, possibly representing early stages of assimilation into
the accretionary wedge. The frontal deformation zone consists of ridges of predominantly landward-verging thrust folds. Seaward-verging backthrust faults at or near the base of the steep slope commonly reach the seafloor. We do not observe a single,
laterally extensive structural offset at the deformation front that might be interpreted as contributing to the 2004 tsunami. Rather, a series of small-offset (tens of metres) faults were noted across this broad zone of the frontal accretionary
wedge. The western boundary of the Aceh (forearc) Basin is the West Andaman strike-slip fault, juxtaposing the accretionary complex's forearc high with basin fill sediments. Neither the seismic nor ROV data show evidence of recent seafloor
displacement along the fault trace. Basin infill demonstrates consistent alongstrike patterns of tilting and seaward subsidence during sedimentation, while modern fill is flat-lying and coherent across the entire basin. Intercalated chaotic layers
interpreted as mass transport deposits may record a history of seismicity, but recent examples of such deposits were not observed on the modern seafloor, either seaward of the deformation front or in the Aceh Basin. Lack of any evidence of faulting,
offset or disruption of sediments within Aceh Basin suggests that there was little impact of the 2004 earthquake in this area. Distributed faults throughout the frontal deformation zone, combined with observations of landward-verging folds at the
deformation front, folding within piggy-back basin sediments, and lack of
evidence of disruption along the West Andaman Fault zone and within the forearc basin all support strain partitioning across the margin. A proposed strong wedge interior may
act as a backstop during major thrust events, constraining deformation to the frontal deformation zone and the slope apron. Tsunami generation in response to the 2004 event did not result from surficial displacements along a single fault or narrow
fault zone at the toe of the deformation front, but was more likely a result of vertical displacement across the entire outer forearc. |
| GEOSCAN ID | 224444 |
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