Liquefaction Potential Analysis in Bucharest City as a Result of the Ground Shaking during Strong Vrancea Earthquakes

Bucharest, the capital of Romania with about 2.5 million inhabitants, is frequently struck by intense, damaging earthquakes (2–3 events per century). The Collaborative Research Center 461 (CRC-461) entitled: “Strong Earthquakes - a Challenge of Geosciences and Civil Engineering” was established in July 1996 and ended in December 2007, but some projects continued until 2010. It was funded by the German Research Foundation and involved the University of Karlsruhe which today belongs to Karslruhe Institute of Technology. The CRC aimed strategic research in the field of strong earthquakes with regional focus on the Vrancea seismic events in Romania. Between 1995–2007 several research works were done in Romania, with the support of several Romanian research institutes and the University of Bucharest. One of the research questions was to study the occurring of liquefaction during strong earthquakes within the shallow sandy layers in Bucharest. In suitable conditions, strong earthquakes can cause, under certain geologic conditions, liquefaction and therewith ground failure as sand boils, lateral spreading, or differentiated subsidence. In the present paper we analyze the liquefaction risk for Bucharest. For this purpose, at 10 representative sites in Bucharest, Seismic Cone Penetration Tests (SCPTu) were executed. An area-wide evaluation of the liquefaction probability in Bucharest was established. The factor of safety (FS) against liquefaction and the probability of liquefaction (PL) were computed from the obtained test-data. For the first time, maps of the liquefaction potential index (Li) for Bucharest were outlined. This map shows how severe the liquefaction phenomena might be during strong Vrancea earthquakes in Bucharest, amplifying the site effects. Keywords: hydrogeologic conditions, liquefaction probability, liquefaction hazard, Bucharest city, strong Vrancea earthquakes

Geological and hydrogeological characterization of the landfill areas located around Bucharest city in the context of environmental management

The process of risk assessment and investigation of potentially contaminated soil and groundwater is highly dependent on a proper understanding of the geological and hydrogeological conditions of the investigated site. The current paper aims at identifying the general geological and hydrogeological conditions of the landfill areas around Bucharest city based on interpretations of the data available in research articles, books, public reports, and geological and hydrogeological maps. Several soil samples were collected, and laboratory analyses were conducted to validate the initial expectations in terms of physical properties of the underlying strata. Results were presented as cross-sections and piezometric maps suitable for developing tridimensional models, conceptual site models and contaminant fate and transport modeling with sufficient accuracy for environmental urban planning. The research provides a quick method which may be used when assessing the general geological and hydrogeological conditions of various sites in environmental studies. The vulnerability of the Romanian legislation in data management and decision-making was also highlighted, therefore a series of recommendations to improve the data availability and quality were provided.

A method to analyse urban heatwaves. Case study - Bucharest City (Romania)

Long-term variation of hourly air temperature obtained from Open Weather, Romania, was analysed in the center of Bucharest city, over a period of 40 years (1980-2020). A computer program to extract summer heatwaves within the study period was written. Analysing the results an extreme heatwave scenario has been defined within the context of climate change and urban influence, to be used in future air and water temperature models.

Sentinel-1 Data for Underground Processes Recognition in Bucharest City, Romania

Urban areas are strongly influenced by the different processes affecting the underground and implicitly the terrestrial surface. Land subsidence can be one of the effects of the urban processes. The identification of the vulnerable areas of the city, prone to subsidence, can be of great help for a sustainable urban planning. Using Sentinel-1 data, by the PSI (persistent scatterer interferometry) technique, a vertical displacements map of Bucharest city has been prepared. It covers the time interval 2014–2018. Based on this map, several subsidence areas have been identified. One of them, holding a thick layer of debris from urban constructions, was analyzed in detail, on the basis of an accurate local geological model and by correlating the local displacements with the urban groundwater system hydraulic heads. The properties of the anthropogenic layer have been characterized by complementary geotechnical and hydrogeological studies. A dynamic instability pattern, highlighted by PSI results, has been put into evidence when related to this type of anthropogenic layer. This thick anthropogenic layer and its connections to the urban aquifer system have to be further analyzed, when the procedures of urban planning and design invoke constructive operations modifying the aquifer dynamics.

Occurrence of invasive insects on woody plants in the main green areas from Bucharest city

In the current context of globalization, biological invasion of alien species has an important impact on environment, economics or human health. Particularly, the spread of these species in urban green areas, is problematic due to several reasons. The aim of this research was to report the presence of invasive insects on woody plants in the main parks across Bucharest (namely Alexandru Ioan Cuza Park, Bucharest Botanical Garden, Cișmigiu Gardens, King Michael I Park, USAMV Campus, Youth Park). Field observations were done during the summer of 2019 (July) and the protocols recently developed by the experts from “Marin Drăcea” National Institute for Research and Development in Forestry were used. It was identified twelve invasive insects species: Aproceros leucopoda (Hymenoptera: Argidae), Cameraria ohridella (Lepidoptera: Gracillariidae), Corythucha arcuata (Hemiptera: Tingidae), Corythucha ciliata (Hemiptera: Tingidae), Cydalima perspectalis (Lepidoptera: Crambidae), Dasineura gledithchiae (Diptera: Cecidomyiidae), Eopineus strobus (Hemiptera: Adelgidae), Macrosaccus robiniella (Lepidoptera: Gracillariidae), Nematus tibialis (Hymenoptera: Tenthredinidae), Obolodiplosis robiniae (Diptera: Cecidomyiidae), Parectopa robiniella (Lepidoptera: Gracillariidae), Prociphilus fraxinifoli (Hemiptera: Aphididae).