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Bottom roughness has a significant effect on acoustic backscattering on the ocean bottom. Sonar systems rely on backscattering and shadows for detecting objects lying on the seafloor. The seafloor is rather complex including craters, gullies, seaweed, rocks, sand ridges, tall obstructions, deep holes and sloping regions. Underwater mines can be hidden around these objects to make detection more difficult. High resolution (1 m 1 m) seafloor data collected by the Navy using multibeam echo sounder (EM710) off the western coast of Saipan was processed by the MB Systems. The advanced least-square method is used to establish new bottom reference level from the EM710 data. After removing the reference level, the high-resolution bathymetry data converts into bottom roughness percentage using a threshold. The calculated bottom roughness percentage is ready to be incorporated into the current Navy doctrine. Two new (gradient and mathematical morphology) methods have been developed in this thesis to calculate the bottom roughness without the reference level. Statistical analysis was conducted to illustrate the added value of the new bottom roughness calculation. http://archive.org/details/newbottomroughne1094517360 Lieutenant, United States Navy Approved for public release; distribution is unlimited.

Der chilenische Teil Patagoniens umfasst die größte zusammenhängende Fjordlandschaft der Südhemisphäre. Ihre Geomorphologie ist bedeutend von den Vergletscherungsperioden der Vergangenheit geprägt. Im März 2008 fand eine großräumige bathymetrische Kartierung des Magellanischen Fjordsystems um 53° S statt. Deren Ergebnisse werden im Rahmen dieser Diplomarbeit vorgestellt. Mithilfe eines portablen Multibeam-Systems konnten Gebiete bei Puerto del Hambre im Mittelteil der Magellan Straße, bei der Insel Tamar im Westen der Magellan Straße, der Seno Glacier mit Swett Kanal und Glacier Bay westlich, bzw. der gesamte Gajardo Kanal östlich des Gletschers Gran Campo Nevado, sowie kleine Felder im Seno Skyring und Seno Otway flächendeckend submarin kartiert werden. Die erhaltenen Karten geben erstmals ein komplettes topografisches Bild der Landschaft und ermöglichen eine Interpretation der Morphologie hinsichtlich der Ausbreitung der Gletscher der Region während und seit dem Last Glacial Maximum (31 250 BP). Es kann an verschiedenen Stellen gezeigt werden, dass sowohl subaquatische Fortsetzungen der Geologie an Land als auch zahlreiche Moränensysteme in der Glacier Bay und dem Gajardo Kanal zweifelsfrei mit einem Fächerecholot erkannt werden können. Zudem wurden die Pockmarks eines Feldes mit Gasaustritten im Seno Otway hochaufgelöst vermessen. In its Chilean part Patagonia comprises the largest continuous fjord belt of the southern hemisphere. Its geomorphology is significantly characterized by past glaciations. In March 2008 a bathymetrical mapping campaign was conducted to cover great areas of the Magellan fjord system at 53° S. The results of this work will be presented in this diploma thesis. Using a portable multibeam system several distinct areas were mapped: a stretch near Puerto del Hambre in the middle of the Magellan Strait; fields near Tamar island in the western part of the Magellan Strait; extensive areas close to glacier Gran Campo Nevado including Seno Glacier, Swett Channel and Glacier Bay in the west and the entire Gajardo Channel in the east; and small fields in Seno Skyring and Seno Otway. For the first time, these maps give a complete view of the topography of the landscape and allow an interpretation of its morphology in respect of the regional extent of glaciation during and since the Last Glacial Maximum (31 250 BP). It can be shown that both subaquatic continuations of geological onland features and various morain systems of Seno Glacier and Gajardo Channel can be doubtlessly detected by means of a swath echosounder. Moreover, pockmarks of a field of gas seepage in Seno Otway has been surveyed with high resolution.

The plate margin offshore Java and the Lesser Sunda islands are located in the eastern portion of the Sunda plate margin, which starts from Burma in the northwest to the Banda arc in the southeast. Different geological configurations in the Sunda plate margin vary enormously from the west to the east due to the variations in sediment supply and the different nature of the oceanic plates along the convergent plate boundary. The Sunda arc hosts earthquakes spanning from moderate magnitude ones to some of the largest earthquakes on Earth. In order to understand the current tectonic structure, the oceanic crust relief, and the temporal evolution of the large volume accretionary mass of the eastern Java and Lesser Sunda margins, we use MCS streamer data and OBS data collected by BGR and GEOMAR to image the plate interface reflection, the upper plate tectonic structure, and velocity attributes of the convergent plates. In this study, we incorporate an innovative seismic processing approach called the Non-Rigid Matching technique applied to the reflection tomography and the pre-stack depth migration and retrieve the structural image of the forearc wedge and the geometry of the plate interface. The depth migrated seismic sections and the bathymetry reveal different scales and shapes of the oceanic relief. By comparing the observed subducting seamount location with the 1994 tsunami earthquake epicentre, the co-seismic slip model, and the aftershock focal mechanisms, we conclude that the seamount acts as an earthquake barrier in the 1994 rupture's propagation process and is weakly coupled in the inter-seismic period before the co-seismic rupture.

Coastal flooding is threatening the personal safety, property, and social development of the low-lying land around the coast worldwide. Stormsurge is one of the main sources of coastal flooding. Tide and surge models can provide timely water level forecasts for coastal management with the early warning of flooding. Although a regional model can be used to study effects of climate change in a specific area, global water level modeling provides some advantages, such as the long-term response of the extreme sea level and coastal flooding due to global warming and comparison of global surge differences between regions. Global hydrodynamic modeling is becoming an increasingly important research topic. Nowadays, with ever increasing resolution, neglected physical processes and parameter uncertainties due to the inaccurate input or empirical values is becoming more and more dominating the model accuracy. At the same time, measurements like the satellite altimeter and the in-situ tide gauges are able to monitor the water level changes, which offers the possibility to estimate uncertain parameters. In this thesis, we develop a parameter estimation scheme and implement it to a global tide and surge model, and subsequently, apply to improve the water level forecast skill. Themain challenges for large-scale parameter assimilation for tide models are in assessing parameter uncertainties, large computational demand, large memory requirement and insufficient observations. In this thesis, we explore these challenges using an application to the Global Tide and Surge Model (GTSM). A computationally efficient and low memory usage iterative estimation scheme is designed and applied to GTSM for bathymetry and bottomfriction coefficient calibration. In addition, we study how to make the best use of spatial sparse distributed observations...

Safe nautical charts require a carefully designed bathymetric survey policy, especially in shallow sandy seas that potentially have dynamic sea floor patterns. Bathymetric resurveying at sea is a costly process with limited resources, though. A pattern on the sea floor known as tidal sand waves is clearly present in bathymetric surveys, endangering navigation in the Southern North Sea because of the potential dynamics of this pattern. An important factor in an efficient resurvey policy is the type and size of sea floor dynamics. The uncertainties of measurement and interpolation associated with the depth values enable the statistical processing of a time series of surveys, using deformation analysis. Currently, there is no procedure available that satisfies the Royal Netherlands Navy requirements. Therefore, a deformation analysis procedure is designed, implemented and tested in such a way that the procedure works on bathymetric data and satisfies the Royal Netherlands Navy requirements. Also, it is necessary to develop a procedure that translates the results into changes of the resurvey policy, taking into account their confidence intervals. To describe the sea floor statistically, we assume the sea floor to consist of a spatial trend function (or characterization) and a residual function (or dispersion). Such a description is called a representation. The covariances between positions are expressed in a covariance function, based on the residual function. The covariance function is used by Kriging, an interpolation procedure that propagates the variances and covariances of the data points to variances of the interpolated values. This approach is used widely for spatial analyses, like the interpolation of a bathymetric data set. The method that we propose uses Kriging to produce a time series of grids of depth values and their variances. Subsequently, it uses deformation analysis, a statistical procedure based on testing theory. Our application of deformation analysis is particularly aimed at the detection of dynamics in areas with tidal sand waves, resulting in parameter estimates for the sea floor dynamics, and their uncertainty. We apply the method to sea floor representations both with and without a sand wave pattern. A test scenario is set up, consisting of a survey of an existing area in the Southern North Sea, for which dynamics are simulated. The results show that the proposed method detects different types of sea floor dynamics well, leading to satisfactory estimates of the corresponding parameters. We show results for the anchorage area Maas West near the Port of Rotterdam, the Netherlands first. The area is divided into 18 subareas. The results show that a sand wave pattern is detected for most of the subareas, and a shore ward migration is detected for a majority of them. The estimated migration rates of the sand waves are up to 7.5 m/yr, with a 95% confidence interval that depends on the regularity of the pattern. The results are in confirmation with previously observed migration rates for the Southern North Sea, and with an idealized process-based model. Thereafter, we analyze several other areas for which a time series of surveys is available in the bathymetric archives of the Netherlands Hydrographic Service, to study the spatial variations in sea floor dynamics. We present results for several sand wave areas and a single flat area. In some of those areas, dredging takes place, to guarantee minimum depths. The results indicate sand wave migration in areas close to the coast, and bed level changes of the order of decimeters. The dominant wavelength of the sand waves varies. We compare our results to literature of the same sand wave areas, in which we find similar migration rates, and different wavelengths. By formulating four indicators, recommendations are made for the resurvey policy on the Belgian and Netherlands Continental Shelf. These indicators follow from the estimates for sea floor dynamics. We present a concept for the shallowest likely depth surface, on which we base two of the indicators. The other two indicators act as a warning: they quantify the potentially missed dynamics, which makes the procedure more robust in case of complicated morphology. We show clear differences in recommended resurvey frequency between the five analyzed regions. We conclude that the designed method is able to use a time series of bathymetric surveys for the estimation of sea floor dynamics in a satisfactory way. Those dynamics may be present on the scale of the sea floor, it may be a local effect, or it may be due to a tidal sand wave pattern. Also, the results are successfully reduced to a set of four indicators, used to improve a resurvey policy. Based on these conclusions, we formulate recommendations on the extrapolation of the results in space and time, on potential adaptations to the designed procedure, and on implementation of the procedure.

Because the seafloor is a complex ecosystem, a multidisciplinary approach must be adopted in order to produce comprehensive habitat maps. Such multidisciplinary projects have been lacking for the Dutch area of the North Sea. To address this lack, the Distribution, structure and functioning of low resilience seafloor communities and habitats of the Dutch North Sea (DISCLOSE) project, funded by the Gieskes- Strijbis Fonds, was initiated. The consortium for the project included three research institutes, as well as the North Sea Foundation. The first of the research institutes was the Delft University of Technology, tasked with the large-scale mapping of the seafloor, using acoustic systems such as the multibeam echosounder (MBES). The second research institute, the University of Groningen (UG), focused on the use of photography and videography to study the seafloor and the epifauna at a smaller, yet more detailed, spatial scale. Finally, the Royal Netherlands Institute for Sea Research (NIOZ), studied the seafloor from both the perspective of particle size and macrofauna using grab-sample data. All of these measurement methods were utilized for the same research areas, in order to maximize the possibility to established links between the sampling methods, and thereby create detailed habitat maps. The work in this thesis focuses specifically on the acoustic results generated within the DISCLOSE project. In recent years the MBES has become the standard tool for the large-scale mapping of the ocean floor. With the MBES, large swaths of the seafloor can be covered in short periods of time. The use of the two-way travel time to measure the bathymetry of the ocean has become very standardized. In addition to measuring the bathymetry, the MBES can also deliver the collocated backscatter product. The appropriate use of backscatter for the classification of seafloor properties and habitats is much less well understood than bathymetry. As such, this is an active field of research. Within Dutch waters, most research has taken place using datasets from the area of the Cleaverbank. Other areas have not been well studied, for example, the southern sandy area. Utilizing MBES backscatter-based seafloor classification in sandy areas is a major focus in this thesis. A dataset from the Brown Bank area of the North Sea was used in order to study seafloor classification over mega ripple structures. A big part of the Southern North Sea is covered in nested sand waves of different sizes. The largest of these is the tidal ridge, with some ten kilometers from crest to crest. The second largest is the sand wave, and the smallest is the mega ripple. Obviously, the main sediment type in this area is sand. Previous research suggests that a difference in grain size is to be expected between the crest of the tidal ridge to the trough. It was not known if a difference in grain size from the crest to the trough of the sand wave or the mega ripple is present, or detectable using MBES backscatter. As such, for this research a few things were very important. Firstly, it was necessary to accurately correct the backscatter for the seafloor slopes in the research area. Next, it was important to have a high spatial resolution for the final classification results. Additionally, a high geo-acoustic resolution was also needed. This final resolution is needed because it is expected that the difference in sediment properties from the trough to crest of a mega-ripple may be just slightly coarser or finer sand. From our research, it was found that it is possible to use MBES backscatter in order to classify the sediment types at the scale of mega ripples. It was found that the coarsest sediments were in the troughs, finer sediments on the stoss side slopes, and a mixture of sediments on the lee side slopes of the mega ripples...

The Tonga-Kermadec arc in the SW Pacific comprises a chain of more than 90 volcanic complexes. A continuous 400-km long chain of volcanic activity along the central portion of the Tonga arc has become the focus of intensive research, extending previous studies that have focused on the southern Kermadec chain. Earlier interpretations of the Tonga arc have focused on a perceived lack of volcanism between ~21°S and ~27°S, adjacent to a bend in the trench caused by the collision of the subducting Louisville Seamount Chain (LSC). During swath mapping in 2002, it was revealed that this portion of the arc, including the Louisville and Monowai segments, is in fact one of the most volcanically active parts of the Tonga-Kermadec system. At this location, a combination of oblique convergence of the Pacific Plate and southward compression due to the collision of the LSC has resulted in left-lateral strike-slip faulting and rifting of the arc crust. This has produced a series of left-stepping arc transverse graben and horst structures that localize the voluminous volcanic activity. For this study, a new 1:250,000 scale geological map of the Louisville and Monowai segments has been constructed as a framework for a quantitative analysis of arc volcanism and the eruptive history of these segments. Two types of volcanoes dominate the arc front: deep caldera systems (collapse structures formed due to the evacuation of magma) within the arc rifts, and smaller volcanic cones between the rifts. The cone volcanoes tend to have small summit craters (<10 km3) whereas the large caldera volcanoes have major depressions of up to 50 km3. The cones are relatively undeformed, whereas the larger calderas are affected by multiple stages of collapse, asymmetric subsidence, and distortion caused by regional stresses. Surveys of the crater walls of the cone volcanoes show a predominance of volcaniclastic deposits, whereas the caldera volcanoes contain a high proportion of coherent lava flows. The caldera volcanoes also show a prevalence of basaltic melts compared to the more andesitic and dacitic cones. The largest caldera volcano is the Monowai volcanic complex (25°53’S) occupying a deep depression (Monowai Rift Graben) that crosses the arc front. The volcanic complex consists of a large caldera (12 km wide, 1600 m deep) and an adjacent stratovolcano (Monowai Cone) rising nearly to sea level. We suggest that the different types of volcanoes along the Louisville and Monowai segments reflect the influence of deep structures within the arc crust that have localized strikeslip and normal faulting.

Geomorphological landforms of the oceanic trenches, their formation and variation of the geometric shapes is a question of special importance to the scientific community in marine geology. The actuality of this question has significantly increased since the beginning of the rapid development of the IT tools and methods of the advanced data analysis, yet its understanding remains patchy. Since the majority of the oceanic trenches are located along the margins of the Pacific Ocean, it plays a central role for their analysis and understanding their formation oceanic trenches. Specific geological conditions, presence of the tectonic subduction zones, vast territory of the Pacific Ocean with complex circulation system, extension of the ’Ring of Fire’, a seismically active belt of the earthquakes and volcanic, make the trenches of the Pacific Ocean highly sensitive to the factors affecting their formation which cause variations in their geomorphic shape forms. In this context, the most representative indicators of the variations in the deep-sea trenches are geological and tectonic factors, such as dynamics of lithosphere crust affecting speed and intensity of plates subduction, magnitude and frequency of the submarine volcanoes causing active sedimentation. Nowadays, studying marine geological phenomena and complex processes by programming and scripting has been a powerful method. Rapid development of the advanced methods of data analysis presented such effective tools as GMT, Octave/MATLAB, R and Python. It is particularly efficient when applied to the massive amounts of marine geological data. Big data processing by advanced scripting is a crucial approach, as algorithms of libraries give access to the accurate and rapid data analysis [373]. Specific information about distant and hard-to-reach deep-sea trenches can be gained for precise visual- ization and analysis of their submarine geomorphology from local to regional and global scales. However, despite all the efforts, there is a lack of uniformity in studying deep-sea trenches, a shortage of systematic mapping of the Pacific trenches and a lack of understanding of the geomorphological variation between the trench profiles in different parts of the ocean: southern and northern, eastern and western, and their response to the geological and tectonic local settings in the places of formation. Therefore, this dissertation develops a systematic approach to monitoring and comparative analysis of the geomorphological shape forms of the deep-sea trenches formed under specific geological and tectonic conditions along the margins of the Pacific Ocean. The study area encompasses Pacific Ocean, and more specifically, includes 20 selected target trenches: Aleutian, Mariana, Philippine, Kuril-Kamchatka, Middle America, Peru-Chile, Palau, Japan, Kermadec, Tonga, Izu-Bonin, New Britain, San Cristobal, Manila, Yap, New Hebrides, Puysegur, Hikurangi, Vityaz and Ryukyu. These are the major trenches of the Pacific Ocean and, therefore, the most representative for the geomorphological modelling. This dissertation identifies tectonic plates formation, slab subduction, historical geological development, earthquakes and submarine volcanoes as the primary types of impact factors affecting trenches formation. Secondary factors include ocean currents, sedimentation and biota contributing to the sedimentation. Seafloor geomorphology in hadal trenches is strongly affected by a variety of factors that necessarily affect the shape of their landforms. Using data modelling, the shapes of the profiles transecting the trenches in an orthogonal direction were compared and analyzed in order to highlight the differences and variations in their geomorphology. The objective of this PhD study is to perform a geomorphological classification of the shape forms of the trenches through ordering them into groups base don the common characteristics of the trenches’ landforms in plan and attaching labels to these groups. Following geomorphological profile shape types have been identifies and trenches are classified into seven types: U-formed (in plan), V-formed (in plan), asymmetric, crescent-formed, sinuous-formed, elongated, cascade-formed. For each type (U, V, asymmetric and so on) characteristic steepness sub-types are identified: strong, very strong, extreme, steep, very steep. Valley slopes are classified as follows: very high, high, moderate, low, based on the curvature degree. Size and valley slope classes are analyzed in the context of physical environment and tectonic and geological development of the area of trench formation. Technical aim of this PhD study was to experiment with and extend current methods of geospatial modelling for geomorphological classification of the submarine landforms of the trenches. Using methods of the advanced data analysis is crucial for the precise and reliable data processing, since understanding seafloor landforms can only be based on the computer-based data modelling due to their unreachable location. The selection of the methodology, tools and algorithms is explained by research objectives and goals. The specifics of the marine geology consists in the high requirements towards data processing. Datasets were processed, computed and analyzed in semi-automatic regime by Machine Learning (ML) approaches, using advanced algorithms of data analysis and effective visualization through application of the advanced programming tools and Generic Mapping Tools (GMT) scripting toolsets. This dissertation presents an automated workflow enabling large-scale profile cross-sectioning aimed at transect geomorphological mapping, quantitative comparative analysis and classification of the 20 trenches of the Pacific Ocean. The methodology of the GMT includes algorithms of sequential scripting for the cartographic visualization and mapping, automatic digitizing of the cross-section transect profiles, and geomorphic modelling of the trenches. In total 50 modules of GMT scripting toolset were trained on extensive datasets collected from 20 trenches across the whole region of the Pacific Ocean. Using high-resolution bathymetric datasets (General Bathymetric Chart of the Oceans (GEBCO), ETOPO1 and Shuttle Radar Topographic Mission (SRTM)), sample transects of the trenches were modeled, analyzed and compared. Variations in shape forms, steepness and curvature were analyzed by computed models for each trench. The tables were converted from QGIS plugins to Python libraries and R packages, and from GMT to Octave via AWK languages. The results revealed variation in the shape and steepness of the submarine geomorphology in 20 trenches of the Pacific Ocean. A strong correlation between the geomorphic profile shapes with geological factors and level of tectonic activities (earthquakes, volcanism, speed of tectonic plate subduction) and the scale of trench steepness, curvature and shape unevenness is confirmed and analyzed. Geomorphological structure of the trenches and dynamics of the tectonic plates subduction are analyzed and assessed at each trench regionally (north, south, west and east Pacific). The novelty of the study consists in presented systematic classification and comparative modelling of the geomorphic profiles of the deep-sea trenches by means of the sequential usage of the advanced scripting toolsets. Technical innovativeness consists in a combination of GIS, GMT, Python, AWK, R and The actuality of this dissertation lies in its strongly multi-disciplinary nature demonstrating a com- bination of the following approaches: 1) systematic multi-source geospatial data analysis; 2) statistical data modelling and processing by libraries of the Python and R, AWK and Octave/Matlab; 3) geological literature analysis; 4) cartographic mapping and modelling by GMT shell scripts and visualization in QGIS. The dissertation contributes to the studies on Technical scripts used for advanced statistical analysis are presented in full in the Appendix A for future replication and reproducible analysis in other trenches of the World Ocean.

Numerical modeling of tsunami propagation at the coastal zone has been a daunting task since high accuracy is needed to capture aspects of wave propagation in the more shallow areas. For example, there are complicated interactions between incoming and reflected waves due to the bathymetry, the run-up and run-down flooding phenomena at the beaches or (other) man-made structures that form the coastline, and intrinsically nonlinear phenomena of wave propagation. Numerical modeling of tsunamis with nested methods in shallower areas is computationally expensive and difficult to use in the operational practice. Meanwhile, if a fixed wall boundary condition is used at a certain shallow depth contour, the reflection properties can be unrealistic. To alleviate this, we develop a so-called effective boundary condition as a novel technique to predict tsunami wave run-up along the coast and offshore wave reflections. The general idea of the effective boundary condition is as follows. From the deep ocean to a seaward boundary, i.e., in the simulation area, the wave propagation is modeled numerically over real bathymetry using either nondispersive, linear, shallow water equations or the dispersive, linear, variational Boussinesq model. The incoming wave is measured at this seaward boundary, and the wave dynamics towards the shoreline and the reflection caused by the bathymetry are modeled analytically. The reflected wave is then influxed back into the simulation area using the effective boundary condition. The location of this seaward boundary point is determined by assessing when nonlinearity starts to play a role in the wave propagation. The modeling of wave dynamics towards the shoreline is achieved by employing the analytical solution of (i) linear shallow water equations and (ii) nonlinear shallow water equations. The linear approach is started with the simplest case, that is flat bathymetry with closed wall boundary condition. Further, a slowly varying bathymetry case is considered. The analytical solution is based on linear shallow water theory and the Wentzel-Kramer-Brillouin approximation, as well as extensions to the dispersive Boussinesq model. Subsequently, in the nonlinear approach, the coastal bathymetry is approximated by using a mean, planar beach. The run-up heights at the shore and the reflection caused by the slope are then modeled based on nonlinear shallow water theory over sloping bathymetry. The coupling between the numerical and analytic dynamics in the two areas is handled using variational principles, which leads to (approximate) conservation of the overall energy in both areas. The numerical solution in the simulation area is based on a variational finite element method. Verifications of the effective boundary condition technique and implementation are done in a series of numerical test cases of increasing complexity, including a case akin to tsunami propagation to the coastline at Aceh, Sumatra, Indonesia. The comparisons show that the effective boundary condition method gives a good prediction of the wave arriving at the shoreline as well as the wave reflection, based only on the information of the wave signal at this seaward boundary point. The computational times needed in simulations using the effective boundary condition implementation show a reduction compared to times required for corresponding full numerical simulations.