Browsing by Author "Tiengo, Rafaela"
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- Detection of Geothermal Anomalies in Hydrothermal Systems Using ASTER Data: The Caldeiras da Ribeira Grande Case Study (Azores, Portugal)Publication . Uchôa, Jéssica; Viveiros, Fátima; Tiengo, Rafaela; Gil, Artur José FreireABSTRACT: Current-day volcanic activity in the Azores archipelago is characterized by seismic events and secondary manifestations of volcanism. Remote sensing techniques have been widely employed to monitor deformation in volcanic systems, map lava flows, or detect high-temperature gas emissions. However, using satellite imagery, it is still challenging to identify low-magnitude thermal changes in a volcanic system. In 2010, after drilling a well for geothermal exploration on the northern flank of Fogo Volcano on São Miguel Island, a new degassing and thermal area emerged with maximum temperatures of 100 °C. In the present paper, using the ASTER sensor, we observed changes in the near-infrared signals (15 m spatial resolution) six months after the anomaly emerged. In contrast, the thermal signal (90 m spatial resolution) only changed its threshold value one and a half years after the anomaly was recognized. The results show that wavelength and spatial resolution can influence the response time in detecting changes in a system. This paper reiterates the importance of using thermal imaging and high spatial resolution images to monitor and map thermal anomalies in hydrothermal systems such as those found in the Azores.
- A Land Cover Change Detection Approach to Assess the Effectiveness of Conservation Projects: A Study Case on the EU-Funded LIFE Projects in São Miguel Island, Azores (2002–2021)Publication . Tiengo, Rafaela; Merino De Miguel, Silvia; Uchôa, Jéssica; Gil, Artur José FreireSmall oceanic islands, such as São Miguel Island in the Azores (Portugal), face heightened susceptibility to the adverse impacts of climate change, biological invasions, and land cover changes, posing threats to biodiversity and ecosystem functions and services. Over the years, persistent conservation endeavors, notably those supported by the EU LIFE Programme since 2003, have played a pivotal role in alleviating biodiversity decline, particularly in the eastern region of São Miguel Island. This study advocates the application of remote sensing data and techniques to support the management and effective monitoring of LIFE Nature projects with land cover impacts. A land cover change detection approach utilizing Rao’s Q diversity index identified and assessed changes from 2002 to 2021 in intervention areas. The study analyzed the changes in LIFE project areas using ASTER, Landsat 8, and Sentinel 2 data through Google Earth Engine on Google Colab (with Python). This methodological approach identified and assessed land cover changes in project intervention areas within defined timelines. This technological integration enhances the potential of remote sensing for near-real-time monitoring of conservation projects, making it possible to assess their land cover impacts and intervention achievements.
- Using Sentinel-1 GRD SAR data for volcanic eruptions monitoring: the case-study of Fogo Volcano (Cabo Verde) in 2014/2015Publication . Tiengo, Rafaela; Pacheco, José M. R.; Uchôa, Jéssica Garcia; Gil, Artur José FreireThe last eruption in the Fogo Volcano, which began in November 2014, was the first eruptive event captured by the Sentinel-1 (S1) mission. The present work sought to complement previous research and explore the potential of utilizing data from the Synthetic Aperture Radar (SAR) S1 mission to better monitor active volcanic areas. S1 Ground Range Detected (GRD) data was used to analyze the changes that occurred in the area before, during, and after the eruptive event and was able to identify the progress of the lava flow and measure the affected area (3.89 km2 in total). Using the GRD data on Google Earth Engine (GEE) platform demonstrated high potential in terms of response time to monitor and assess eruptive scenarios in near-real-time, which is fundamental to mitigate risks and to better support crisis management.