https://www.um.edu.mt/library/oar/handle/123456789/62490 Fri, 10 Apr 2026 07:41:23 GMT 2026-04-10T07:41:23Z https://www.um.edu.mt/library/oar/handle/123456789/107482 Title: An integrated assessment of the impact of anchoring on seafloor integrity (MSFD Descriptor 6) within a major bunkering area of the Maltese islands Abstract: International shipping is a fundamental driver for the global economy. As the shipping industry grows, so does the demand for high-capacity vessels, which led to concerns on how these vessels interact with the marine environment. While waiting to access port facilities and services, vessels may anchor to reduce fuel consumption and to prevent the vessel from drifting. However, anchoring is one of the primary causes of mechanical disturbance to the seafloor and benthic habitats and ecosystems. Locating and quantifying anchoring pressure would enable the marine environment to be managed better so that damage to the seafloor as a result of anchoring is mitigated. The Automatic Identification System (AIS) can be used for identifying and quantifying the anchoring pressure in those areas under investigation. AIS transmits information (e.g. position, type, size) of a vessel to other vessels and coastal stations. This study aims to assess the anchoring pressure in one of the bunkering areas strategically located around the Maltese Islands by using the AIS data collected by the AIS antenna located at the University of Malta, Msida. Anchoring pressure is determined through the development of an arbitrary index using the AIS data. Additionally, the same AIS data is used to produce several GIS maps depicting the location and size of the vessels within the confines of the bunkering area as mentioned above as well as several plots depicting anchoring pressure based on vessel type, seasonality, and density. Description: M.Sc.(Melit.) Wed, 01 Jan 2020 00:00:00 GMT https://www.um.edu.mt/library/oar/handle/123456789/107482 2020-01-01T00:00:00Z https://www.um.edu.mt/library/oar/handle/123456789/86242 Title: Performance evaluation of the Malta seismic network Abstract: At the beginning of the project, the permanent Malta Seismic Network (MSN) consisted of 6 permanent stations, 3 being located in Malta, 2 in Gozo and 1 in Comino. The MSN is operated by the Seismic Monitoring Research Group (SMRG) within the Department of Geosciences at the University of Malta. For a 12-month period between August 2017 and August 2018 a temporary network of 6 additional stations were installed in various locations around the Maltese archipelago as part of the FASTMIT project. This extension to the permanent Malta Seismic Network (MSN) increased the number of recording stations to 12, offering an unprecedented opportunity for working with seismological data. The performance of each station in terms of its background level of noise was evaluated. This consisted of an analysis of noise (both of natural and anthropic origin) in terms of seasonal variations by considering 15-day periods in winter and in summer for each station. Via computation of probability density functions of power spectral density (PSDPDF) the level of background noise and its origin, in different frequency bands, was analysed. Furthermore, noise recordings were also used to perform a horizontal-to-vertical spectral ratio (HVSR) where several amplification peaks were identified for stations underlain by a significant thickness of Blue Clay. This was used to present tentative time-delay corrections related to non-uniform topography and geology. Initially, the performance of the extended MSN as a beamforming array was assessed for a limited number of well-located teleseismic and regional Mediterranean events of large magnitudes, by comparing the locations derived from the software package Generic Array Processing (GAP) to that provided by international bulletins such as the EuropeanMediterranean Seismological Centre (EMSC), for which results were promising. However, the main focus of this project was the potential of the MSN and the extended network to be used as a steered, small-aperture array for locating regional earthquakes. Using data archived by the SMRG, seismic activity up to 150 km from the Maltese archipelago was analysed by investigating 21 events which were only recorded locally in addition to 6 events which were also located by neighbouring networks affiliated with the Istituto Nazionale Geofisica e Vulcanologia (INGV). All these local events had already been located using singlestation polarisation algorithm (SSL) and where possible, using the multiple SSL technique, incorporated within LESSLA. This technique is known to suffer from back-azimuth (BAZ) estimation. GAP was used to investigate whether the array could yield improvements in the BAZ. Seismic traces recorded at the 12 stations were used to perform a grid search for slowness, ranging between – 25 s / ° and + 25 s / °. Using beamforming, a value for optimal BAZ was obtained at maximum beam power using the program slow2d. Generally, the standard deviation for BAZ for these low-magnitude events was below ± 10 °, with the standard deviation typically depending on the quality of the seismic traces, the magnitude of the event, and the epicentral distance from the reference station WDD. The epicentral solutions were obtained using the epicentral distances previously calculated by the SMRG and available on the online portal, derived using an S-P time calibration curve. The performance of the network when including only the 6 permanent stations, and also when introducing tentative corrections compensating for varying geology and topography, was also analysed for any effect on BAZ estimation. The locations obtained using GAP were also compared to other methodologies such as least square fitting techniques using elocate. The results indicate an improved ability to calculate BAZ for small earthquake activity around the Maltese Islands, especially to the south-east of the archipelago, when using GAP. Moreover, it can also be concluded that seismicity in the study area considered is more clustered than originally thought and is tentatively linked to active faults to the south-east of the archipelago. Description: M.SC.GEOSCIENCES Wed, 01 Jan 2020 00:00:00 GMT https://www.um.edu.mt/library/oar/handle/123456789/86242 2020-01-01T00:00:00Z https://www.um.edu.mt/library/oar/handle/123456789/85567 Title: Comprehensive hydrodynamic model validation using satellite observations around the Maltese islands Abstract: Sea surface temperature (SST) constitutes one of the most important environmental parameters and is a critical factor mainly in climatology meteorology and oceanography. Changes in SST affect the Earth's atmosphere, the underlying water currents and the balance of the biological component of the earth ecosystem. They also contribute to the global ocean energy exchange. Observing and predicting SST is fundamental since SST plays a pivotal role in the ocean-atmosphere coupled system and therefore is an important indicator of the Earth’s climate. The Malta Shelf model ROSARIO-II hydrodynamical is an eddy-resolving, primitive equation, sigma level shelf-scale numerical model. It is developed, maintained and run in operational mode by the Physical Oceanography Research Group (University of Malta), providing daily forecast of sea salinity, sea currents and sea temperature around the Maltese Islands. Through this project, the modelled SST was validated against observed SST using remotely-sensed satellite measurements (Copernicus Marine Environment Monitoring Service products (Sentinel-3). In this study, the validity of the model is assessed in order to demonstrate that the model possesses a satisfactory range of accuracy consistent with the intended application of the model. The analysis includes the comparison of available data in terms of the face validity, by generating scripts to visually compare properties such as seasonal and monthly SST and to compare variability in terms of time series. Distributional and value validity is studied by comparing modelled SST with satellite derived estimates, means, standard deviations, and spatial patterns. The validation methodology is not limited to pointwise comparing the datasets, but the research extends to exploring possible time-lags in SST predictions, SST zone intensity variation and high- and lowSST spatial displacement relative to the observations. Patterns and features observed in both modelled and observed SST are analysed. Methods include the generation of specific scripts for basic statistics analysis, pointwise analysis, cluster analysis, time lag analysis, and other specialized analysis. Two new validation indicators are generated: The Histogram Intersection Coefficient and the Performance Index that assesses the model performance based on clustering analysis. Description: M.SC.GEOSCIENCES Wed, 01 Jan 2020 00:00:00 GMT https://www.um.edu.mt/library/oar/handle/123456789/85567 2020-01-01T00:00:00Z https://www.um.edu.mt/library/oar/handle/123456789/85564 Title: Investigation of the dynamic properties of coastal and other geomorphological features through the use of ambient vibrations Abstract: The north western coastline of Malta features highly destabilised rock masses due to a layer of hard Upper Coralline Limestone on top of soft clay. This geological layering causes instability, which triggers the fracturing of the upper rock layers and large-scale mass detachments. These landslide processes stimulate lateral spreading phenomena. The Maltese coastline is a natural attraction but also poses geological risks especially to areas of cultural and national importance. Therefore, to mitigate hazards, it is important to understand the vulnerability and the dynamic properties of unstable blocks. The aim of this study was to find a correlation between the natural frequency obtained from experimental results and that generated from numerical modelling, on the behaviour of coastal detachment processes. Two sites around the Maltese coastline were chosen for this research: Selmun and Anchor Bay, both of which are located in the north western part of Malta. These locations consist of several examples of slab detachment at different stages. Ambient noise measurements which were recorded using the Micromed Tromino® were taken at these sites from previous studies. These measurements were taken on unstable blocks at both sites and were analysed using the Horizontal-To-Vertical Spectral Ratio to determine their natural frequency. Moreover, by using photogrammetric techniques, 3D aerial photos were created to examine the extent and dimensions of detached slabs near the cliff edge. 3D models of blocks were created with Autodesk Meshmixer and transferred onto a finite element code ANSYS, to study the vibrational behaviour of blocks detached at different depths of fractures. Using numerical modelling, the natural frequency of these models was determined and compared to the experimental data obtained using ambient noise. Furthermore, other geomorphological features such as isolated hills like Laferla Cross, were also considered to study the thickness of the underlying geology in relation to vibrational modes. Description: M.SC.GEOSCIENCES Wed, 01 Jan 2020 00:00:00 GMT https://www.um.edu.mt/library/oar/handle/123456789/85564 2020-01-01T00:00:00Z