Relocation of intermediate and deep earthquakes of Tyrrhenian Sea area through joint hypocenter determination for the period 1962–1979, has allowed a more detailed definition of the geometry of this peculiar Benioff zone. Earthquakes dip along a quasi-vertical plane to 250 km depth; there is a 50° dip in the 250–340 km depth range, and a low dip angle to 480 km depth. The structure sketched from the hypocenters is almost continuous, but most energy has been released in the 230–340 km depth interval. An evaluation of fault plane solutions of intermediate earthquakes in this area indicates predominance of down-dip compressions in the central part of the slab. At the border, strike-slip motion occurs independent of depth. Some earthquakes that occurred at intermediate depth (less than 100 km) along the Ionian margin of Calabria show predominance of reverse faulting, with the P-axis oriented SE-NW. However, shallow earthquakes in the Calabria-Sicily region indicate a more complex motion, with predominance of normal faulting. A possible interpretation of these features according to the available geological history, which involves subduction of continental lithosphere, is discussed. 相似文献
Technical and institutional capacities are strongly related and must be jointly developed to guarantee effective natural risk governance. Indeed, the available technical solutions and decision support tools influence the development of institutional frameworks and disaster policies. This paper analyses technical and institutional capacities, by providing a comparative evaluation of governance systems in Italy and France. The focus is on two case studies: Naples and Guadeloupe. Both areas are exposed to multiple hazards, including earthquakes, volcanic eruptions, landslides, floods, tsunamis, fires, cyclones, and marine inundations Cascade and conjoint effects such as seismic swarms triggered by volcanic activity have also been taken into account. The research design is based on a documentary analysis of laws and policy documents informed by semi-structured interviews and focus groups with stakeholders at the local level. This leads to the identification of three sets of governance characteristics that cover the key issues of: (1) stakeholders and governance level; (2) decision support tools and mitigation measures; and (3) stakeholder cooperation and communication. The results provide an overview of the similarities and differences as well as the strengths and weaknesses of the governance systems across risks. Both case studies have developed adequate decision support tools for most of the hazards of concern. Warning systems, and the assessment of hazards and exposure are the main strengths. While technical/scientific capacities are very well developed, the main weaknesses involve the interagency communication and cooperation, and the use and dissemination of scientific knowledge when developing policies and practices. The consequences for multi-risk governance are outlined in the discussion. 相似文献
A coupled wave and ocean model is applied to the region of Galway Bay in the west of Ireland, using the numerical modelling suite COAWST. The coupled model was validated in a previous study. Here we focus on the impact of the currents and sea level on the sea state during Storm Hector (2018/06/14). The purpose of the research is to improve the wave dynamics knowledge specifically in Galway Bay by highlighting and quantifying the dominant current-induced mechanisms on the sea state observed numerically. We want to know where wave-current interaction is modifying the sea state in the bay, and if the change is significant to justify the use of a coupled model for an operational application. We show that the impacts of the tidal sea surface height on bottom friction and of the current-induced refraction on the spatial distribution of the waves are the dominant mechanisms. Those two effects are well-documented and observed in the literature already. A strong feedback impact of the coupling is also put into evidence. The wave-induced response in terms of currents leads to a noticeable variation in terms of wave height. Less documented in the literature, we discuss the link between current-induced refraction and the reduction of wave generation by wind.
Vertical profiles of dissolved organic carbon (DOC) from eight hydrological stations in the Tyrrhenian Sea, Sardinia Channel and Algerian Sea, are reported. DOC exhibits concentrations ranging from 58 to 88 μM in surface water, 43–57 μM in the intermediate layer and 49–63 μM in deep waters. The assessment of the hydrological characteristics allows different water masses in the study area to be identified; moreover, different hydrological processes are observed in the Tyrrhenian and Algerian basins. DOC exhibits different values in the different water masses. The lowest DOC concentrations (43–46 μM) were found in the Tyrrhenian Levantine Intermediate Water (LIW). Correlations between DOC and apparent oxygen utilization (AOU), investigated within each water mass, exhibit different behaviors in the intermediate and deep waters, suggesting the occurrence of different processes of oxygen consumption in the different water masses. 相似文献
The record of felt earthquakes around Naples Bay in southern Italy is probably complete since the mid-15th century. According to this record, intense earthquake swarms originating beneath Campi Flegrei, an explosive caldera located along the north coast of Naples Bay, have occurred only twice: (1) before the only historical eruption in Campi Flegrei in 1538; and (2) from mid-1983 to December 1984. Earthquake activity during the earlier period, which began at least a few years, and possibly as many as 30 years, before the 1538 eruption, damaged many buildings in the city of Pozzuoli, located near the center of Campi Flegrei. Minor seismic activity, which consisted of only a few felt earthquakes, occurred from 1970 to 1971. The second period of intense earthquake swarms lasted from mid-1983 to 1984, again damaging many buildings in Pozzuoli. Two periods of uplift along the shoreline within Campi Flegrei have also been noted since the mid-15th century: (1) during the few decades before the 1538 eruption; and (2) as two distinct episodes since 1968. Uplift of a few meters probably occurred a few decades before the 1538 eruption; uplift of as much as 3.0 m has occurred in Pozzuoli since 1968.These similarities strongly suggest that, for the first time in 440 years, the same process that caused intense local earthquake swarms and uplift in the early 1500's and led to an eruption in 1538, has again occurred beneath Campi Flegrei. Though no major seismicity or uplift has occurred since December 1984, because of the large amount of extensional strain accumulated during the past two decades, if a third episode of seismicity and rapid uplift occurs, it may lead to an eruption within several months after the resumption of activity. 相似文献