Slope stability along active and passive continental margins ... - E-LIB

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2 Geotechnical characteristics and slope stability along the Uruguayan and northern Argentine margin (Sosa 1998). Recent documented earthquakes occurred in the years of 1849, 1888, and 1988 A.D. (for locations of epicenters, see Fig. 2.1A, Sosa 1998). The epicenter and magnitude of the 1988 earthquake is not conclusively defined. Seismological observatory of the University of Brazil showed the epicenter located 36.5°S, 53.5°W, +/- 100 km with the regional magnitude of 3.9, whereas, NEIC (National Earthquake Information Center) recorded the epicenter of 36.27°S, 52.73°W with a body wave magnitude of 5.1 m b (Sosa 1998). Here we choose the seismic parameters as the epicenter of 36.27°S, 52.73°W with a body wave magnitude of 5.2 m b following Assumpção (1998). Based on the seabed morphology, our study area is separated into two distinct subareas: northern mass movements dominated area (NS) on the Uruguayan slope and southern canyons dominated area (SC) on the northern Argentine slope. Krastel et al. (2011) refer to NS as the “northern slide area” and “drift-and-scarp area”. NS is characterized by a smooth topography and gentle slopes (1-3°) typical of margins where deposition prevails over erosion (Ewing and Lonardi 1971). Several scarps (Fig. 2.1B, C) and mass transport deposits (MTDs) (Figs. 2.2A, A’, B, B’) at 1200-2800 m were found in NS (detail descriptions see Krastel et al. 2011). SC is characterized by the flat Ewing terrace, which is dissected by canyons at ~1400 m (e.g., Mar del Plata Canyon and Querendi Canyon, Fig 2.1D). The slope below the Ewing terrace is steep (3-7°), suggesting that erosion has been the main process shaping the slope of SC (Ewing and Lonardi 1971). No clear MTDs were found in the sedimentary sequences upper slope and flanks of the Querendi Canyon (Fig. 2.2C, D). However, MTDs were imaged in the thalweg of the Querendi Canyon, which suggests headward erosion is common in this canyon (Fig. 9 of Krastel et al. 2011) At present, sedimentation in the study area is strongly influenced by high fluvial discharge of the Rio de la Plata River and strong bottom current forces. The sediments of the study area are generally divided into a clayey silt NS part and sand SC part (Huppertz 2011). The boundary between the two environments is located at the position of the Brazil Malvinas confluence (BMC, ~37°S). North of the BMC, high quantities of terrigenous sediments (~80×10 6 ton/yr) discharged by Rio de la Plata River, containing 75% coarse to medium silt, 15% fine to very fine silt and 10% clay (Giberto et al. 2004), are swept northwards by alongshore currents and deposited at the Uruguayan continental shelf and slope (Piola et al. 2005); sediment transport is dominated by the southward flow of North Atlantic Deep Water (NADW) at the Uruguayan slope in water depths between 2000-4000 m. South of the BMC, coarse fluvial sediments are trapped with the estuary and occasionally carried directly down slope by turbidity current (Garming et al. 2005); most of the surficial sediments at the northern Argentine slope have been carried and reworked northward by water masses in different depths including the Antarctic Intermediate Water (AAIW, ~500-1000 m), the Circumpolar Deep Water (~1000-3500 m) and the Antarctic Bottom Water (AABW, >3500 m) (more details, see Piola and Matano 2001). 43
2 Geotechnical characteristics and slope stability along the Uruguayan and northern Argentine margin Fig. 2.1 (A) Map showing the location of the study area and the oceanographic setting along the Uruguayan and northern Argentine margin. Red dots indicate the epicenters of the 1848, 1888 and 1988 earthquakes. MC: Malvinas Current, AAIW: Antarctic Intermediate Water, CDW: Circum Polar Deep Water, AABW: Antarctic Bottom Water, BC: Brazil Confluence, and NADW: North Atlantic Deep Water. (B) and (C) Bathymetric contour maps of NS. Red lines indicate the position of Parasound and seismic profiles. Black dots indicate core locations. Black dashed lines indicate the distances to the epicenter of the 1988 earthquake. D) Bathymetric map of SC. Modified after Krastel et al. (2011). 44
Page 1 and 2: Slope stability along active and pa
Page 3 and 4: Name: Ai, Fei Datum: 15-07-2013 Ans
Page 5 and 6: 3 Submarine slope stability assessm
Page 7 and 8: Abstract old landslide named Northe
Page 9 and 10: Zussamenfassung geringeren inneren
Page 12 and 13: 1 Introduction 1.1 Motivation In re
Page 14 and 15: 1 Introduction 1.2 Submarine slope
Page 16 and 17: 1 Introduction 1.2.2 Preconditionin
Page 18 and 19: 1 Introduction 1.2.3 Geotechnical s
Page 20 and 21: 1 Introduction S u FS ' z sin cos
Page 22 and 23: 1 Introduction Fig. 1.5 Location ma
Page 24 and 25: 1 Introduction et al. 2011). The sl
Page 26 and 27: 1 Introduction occurrence of a subs
Page 28 and 29: 1 Introduction (1) superficial slop
Page 30 and 31: 1 Introduction measurements; the wo
Page 32 and 33: 1 Introduction equal to the vertica
Page 34 and 35: 1 Introduction The conductivity val
Page 36 and 37: 1 Introduction 1.4 Outline of the t
Page 38 and 39: 1 Introduction 1936. pp 60-64. Coch
Page 40 and 41: 1 Introduction M78/3. Sediment tran
Page 42 and 43: 1 Introduction 217-240. Morgenstern
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Page 94 and 95: 5 Conclusion and outlook 5.1 Conclu
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Appendix A: Core descriptions, phys
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Appendix B: Core descriptions, phys
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