| dc.description.abstract | Submarine landslides are a mixture of rock, soil, and fluids moving downslope due to a slope's initial event of mechanical failure. These phenomena play a significant role in the evolution of continental margins. On the one hand, sediment transport processes from the continental shelf to the foot of the continental slope are meaningful. On the other hand, submarine landslides play a critical role in shaping the geomorphology of the seafloor. In addition, they have the potential to affect coastal infrastructure, submarine telecommunications cables, and pipelines, and generate tsunamis and avalanches. Thus, the negative consequences of submarine landslides have been socially and economically significant.
In the Colombian southern Caribbean margin, submarine landslides are closely related to regional tectonic dynamics and show distinctive characteristics in canyon walls, channel-levee systems, tectonically controlled ridges, and continental shelf break. Previous studies have highlighted the importance of landslides as geohazards analyzing the largest landslides observed in the bathymetry or studying their presence in limited areas of the Colombian southern Caribbean.
This study shows a regional analysis of the occurrence of submarine landslides in the southern Colombian Caribbean. The geomorphological analysis was based on a bathymetric model that included seismic cubes and multibeam bathymetric surveys with resolutions ranging between 10 and 100 meters. These data involved areas from the continental shelf break to the foot of the continental rise making it easier to obtain a regional image of the seafloor in which the interpretation of landslide extended toward areas without 3D seismic information. After mapping the geographic distribution of submarine landslides, their relationship with ground conditions, including seafloor geomorphology, slope degree, fault presence, the Bottom Simulator Reflector (BSR), and Mass-Transport Complexes (MTCs), was analyzed. Finally, a preliminary map of landslides susceptibility was carried out following the landslide Weight index (Wi), a method proposed by Van Westen in 1997, and overpressure conditions in the sedimentary sequence were interpreted to see the relationship between both phenomena.
Chapter 1. This chapter presents a detailed geomorphological mapping of submarine landslides carried out using a high-resolution 3D seismic survey. This mapping allowed obtaining a statistical analysis and a complete interpretation of geomorphological characteristics of the seafloor and subsoil patterns to define the morphology of landslides and their distribution of occurrence, and their relationship with structural deformation. Results suggest that landslides in the study area are related to thrust faults and structural ridges of the Southern Sinú Fold Belt (SSFB) that greatly contribute to the filling of intra-slope sub-basins isolated from the continental shelf.
Chapter 2. This chapter shows the mapping of the southern Caribbean seafloor using seismic cube surveys and multibeam bathymetry data in an area encompassing 59,471 km2, which allowed analyzing the regional distribution of submarine landslides and simplifying their occurrence through the construction of a conceptual framework for a better insight. Distinctive characteristics were found for submarine landslides associated with canyon walls, channel-levee systems, tectonically controlled ridges, and continental shelf break. Also, can be observed that Mass-Transport Complexes (MTCs) result from the accumulation of mass movement originating both in the continental shelf break and the channel-levee systems. However, the size of MTCs does not represent individual events but rather the accumulation of multiple events. This fact made it possible to estimate a landslide susceptibility map which suggests the following considerations: Firstly, structural ridges and adjacent intra-slope sub-basins related to the South Caribbean Deformed Belt (SCDB) are more likely to be landslide hazards. Secondly, the continental shelf break and channelized systems produce a moderate landslide hazard potential. Thirdly, deep marine systems with a slope less than five degrees (<5°) show the lowest landslide hazard potential.
Chapter 3. This chapter presents the analysis carried out on overpressures in the Sinú Offshore basin, summarizing the observations from well data, seismic data, and basin modeling. Overpressure zones were observed to match low velocities of sound from well logs and seismic cubes. Likewise, wells with the highest overpressures (>15 ppg) are located in the south of the study area, while wells located in the northern part of the basin showed lower overpressure conditions (<15 ppg). It is concluded that overpressures have a more direct relationship with anticlinal-type compression structures than with other geological phenomena, such as high sedimentation, which is certainly more related to landslides and Mass-Transport Complexes (MTCs) characteristic on the surface of the seafloor. | |
