Browsing by Subject "Sumatra"
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Item Endohelminths from six rare species of turtles (Bataguridae) from Southeast Asia confiscated by international authorities in Hong Kong, China(Texas A&M University, 2004-09-30) Murray, Rebecca AnnSpecimens of 6 species of threatened, vulnerable, and endangered turtles (Cuora amboinensis, Cyclemys dentata, Heosemys grandis, Orlitia borneensis, Pyxidea mouhotii, and Siebenrockiella crassicollis) belonging to family Bataguridae, were confiscated in Hong Kong, China on 11 December 2001 by international authorities. Endohelminth studies on these turtle species are scarce, and this study provided a rare opportunity to examine a limited number of specimens for endohelminths. Ten different parasite species were collected and there were 16 new host records. This is the first record of a parasite from P. mouhotii. The parasite prevalences found in this study provide a basis for a better understanding of the phylogenetic relationships of the family Bataguridae to other families, especially Testudinidae. Based on known life cycles, parasites found provided an indication of food preferences of these 6 turtle species that support previous studies of the turtles' feeding habits. However, the results of the parasite survey from O. borneensis provided additional feeding habit information. The list of endohelminths herein is intended to provide a foundation for future parasite studies of the 6 species of Asian turtles.Item Geophysical investigations in the Nankai Trough and Sumatran subduction zones(2011-12) Martin, Kylara Margaret; Gulick, Sean P. S.The 2004 Sumatra-Andaman and the 2011 Tohoku-Oki earthquakes demonstrate the importance of understanding subduction zone earthquakes and the faults that produce them. Faults that produce earthquakes and/or tsunamis in these systems include plate boundary megathrusts, splay faults (out of sequence thrusts), and strike-slip faults from strain partitioning. Offshore Japan, IODP Exp. 314 collected logging while drilling (LWD) data across several seismically-imaged fault splays in the Nankai Trough accretionary prism. I combine LWD resistivity data with a model of fluid invasion to compare the permeabilities of sands. My results indicate that sands within faulted zones are 2-3 orders of magnitude more permeable than similar undisturbed sands. Therefore fault zones are likely to be fluid conduits within the accretionary wedge. Fluids can affect the physical and chemical properties of the faulted material, increasing pore pressures and effectively lubricating the faults. Fluids play an important role in fault slip, but hazard analysis also requires an understanding of fault geometry and slip direction. Both Japan and Sumatra exhibit strain partitioning, where oblique convergence between tectonic plates is partitioned between the megathrust and strike-slip faults proximal to the arc. Offshore Sumatra, I combine profiles from a 2D seismic survey (SUMUT) with previous bathymetry and active seismic surveys to characterize the West Andaman Fault adjacent to the Aceh forearc Basin. Along this fault I interpret transpressional flower structures that cut older thrust faults. These flower structures indicate that the modern West Andaman Fault is a right lateral strike-slip fault and thus helps to accommodate the translational component of strain in this highly oblique subduction zone. Offshore the Kii Peninsula, Japan, I analyze a trench-parallel depression that forms a notch in the seafloor just landward of the megasplay fault system, along the seaward edge of the forearc Kumano Basin. Using a 12 km wide, 3D seismic volume, I observe vertical faults and faults which dip toward the central axis of the depression, forming apparent flower structures. The along-strike geometry of the vertical faults makes predominantly normal or thrust motion unlikely. I conclude, therefore, that this linear depression is the bathymetric expression of a transtensional fault system. While the obliquity of convergence in the Nankai Trough is small (~15 degrees), this Kumano Basin Edge Fault Zone could be due to partitioning of the plate convergent strain. The location of the West Andaman Fault and KBEFZ within the forearc may be controlled by the rheology contrast between active accretionary wedges and the more stable crust beneath forearc basins.Item Morphology and structure of the accretionary prism offshore North Sumatra, Indonesia and offshore Kodiak Island, USA : a comparison to seek a link between prism formation and hazard potential(2016-08) Frederik, Marina Claudia Geraldina; Gulick, Sean P. S.; Austin, James Albert; Bangs, Nathan L. B.; Lavier, Luc L; Barnes, Jaime D; McNeill, Lisa CSumatra and Kodiak Islands experienced recent megathrust earthquakes with devastating tsunami; recurrence of large earthquakes is predicted. Studies of the accretionary prism offshore of northern Sumatra, 1-7°N and 92-97°E, reveal a steep outer slope (5-12°), a plateau ~100-120 km wide, and a steep inner slope adjacent to the Aceh Basin. Three primary structural zones are consistent along strike where a predominantly landward vergence zone exists from the deformation front for a distance ~70 km landward. An extended landward vergence zone is not common; for northern Sumatra, a seaward dipping rigid backstop may be the reason, which assists subsequent younger accreted sediment to form the observed zone. The prism toe region shows prominent mass failures presumably related to activation of thrust faults and/or the shaking in response to the 2004 Sumatra-Andaman earthquake (Mw 9.1). These seafloor changes suggest that the 2004 rupture energy reached near the accretionary prism toe. The rigid backstop in the inner wedge together with the suggested dynamic backstop within the outer wedge, and the consolidated sediment on the outer slope form a rigid block dynamically, which together allows earthquake rupture to propagate under it and farther seaward toward the Sunda Trench, resulting in enhanced tsunami potential. Along the Aleutian Trench offshore of Kodiak Island, 145-155° W and 55-58° N, exist a distinct horizon, associated with the onset of the Surveyor Fan sedimentation along which the preferred zone forms. Most if not all of the sediment beneath this horizon seemed subducted, smoothing the high relief of the subducting plate. Subduction of large-buried seamounts begins with creation of a proto-thrust zone seaward of the existing deformation front. As a seamount reaches the deformation front, steepening of the prism toe occurs by formation of out-of-sequence thrusts. Upon further subduction, a deformation front jump occurs where the outer limit of proto-thrust zone becomes the new deformation front. This study contributes insights to other subduction zones with similar characteristics such as thick incoming sediment, subducting seamounts, and/or recent megathrust events. This study also underlines the need to establish fundamental time series data sets for mitigation efforts in hazard-prone areas.