Macroseismic effects highlight site response in Rome and its geological signature     

Paola Sbarra  Valerio De Rubeis  Emiliano Di Luzio  Marco Mancini  Massimiliano Moscatelli  Francesco Stigliano  Patrizia Tosi  Roberto Vallone 《Natural Hazards》2012,62(2):425-443

A detailed analysis of the earthquake effects on the urban area of Rome has been conducted for the L??Aquila sequence, which occurred in April 2009, by using an online macroseismic questionnaire. Intensity residuals calculated using the mainshock and four aftershocks are analyzed in light of a very accurate and original geological reconstruction of the subsoil of Rome based on a large amount of wells. The aim of this work is to highlight ground motion amplification areas and to find a correlation with the geological settings at a subregional scale, putting in evidence the extreme complexity of the phenomenon and the difficulty of making a simplified model. Correlations between amplification areas and both near-surface and deep geology were found. Moreover, the detailed scale of investigation has permitted us to find a correlation between seismic amplification in recent alluvial settings and subsiding zones, and between heard seismic sound and Tiber alluvial sediments.  相似文献   

High-temperature emplacement of the Cerro Galán and Toconquis Group ignimbrites (Puna plateau,NW Argentina) determined by TRM analyses     

Chiara Lesti  Massimiliano Porreca  Guido Giordano  Massimo Mattei  Raymond A. F. Cas  Heather M. N. Wright  Chris B. Folkes  Josè Viramonte 《Bulletin of Volcanology》2011,73(10):1535-1565

Estimates of pyroclastic flow emplacement temperatures in the Cerro Galán ignimbrite and Toconquis Group ignimbrites were determined using thermal remanent magnetization of lithic clasts embedded within the deposits. These ignimbrites belong to the Cerro Galán volcanic system, one of the largest calderas in the world, in the Puna plateau, NW Argentina. Temperature estimates for the 2.08-Ma Cerro Galán ignimbrite are retrieved from 40 sites in 14 localities (176 measured clasts), distributed at different distances from the caldera and different stratigraphic heights. Additionally, temperature estimates were obtained from 27 sample sites (125 measured clasts) from seven ignimbrite units forming the older Toconquis Group (5.60–4.51 Ma), mainly outcropping along a type section at Rio Las Pitas, Vega Real Grande. The paleomagnetic data obtained by progressive thermal demagnetization show that the clasts of the Cerro Galán ignimbrite have one single magnetic component, oriented close to the expected geomagnetic field at the time of emplacement. Results show therefore that most of the clasts acquired a new magnetization oriented parallel to the magnetic field at the moment of the ignimbrite deposition, suggesting that the clasts were heated up to or above the highest blocking temperature (T _b) of the magnetic minerals (T _b = 580°C for magnetite; T _b = 600–630°C for hematite). We obtained similar emplacement temperature estimations for six out of the seven volcanic units belonging to the Toconquis Group, with the exception of one unit (Lower Merihuaca), where we found two distinct magnetic components. The estimation of emplacement temperatures in this latter case is constrained at 580–610°C, which are lower than the other ignimbrites. These estimations are also in agreement with the lowest pre-eruptive magma temperatures calculated for the same unit (i.e., 790°C; hornblende–plagioclase thermometer; Folkes et al. 2011b). We conclude that the Cerro Galán ignimbrite and Toconquis Group ignimbrites were emplaced at temperatures equal to or higher than 620°C, except for Lower Merihuaca unit emplaced at lower temperatures. The homogeneity of high temperatures from proximal to distal facies in the Cerro Galán ignimbrite provides constraints for the emplacement model, marked by a relatively low eruption column, low levels of turbulence, air entrainment, surface–water interaction, and a high level of topographic confinement, all ensuring minimal heat loss.  相似文献   

IFKIS-Hydro: an early warning and information system for floods and debris flows     

Hans Romang  Massimiliano Zappa  Nadine Hilker  Matthias Gerber  François Dufour  Valérie Frede  Dominique Bérod  Matthias Oplatka  Christoph Hegg  Jakob Rhyner 《Natural Hazards》2011,56(2):509-527

IFKIS-Hydro is an information and warning system for hydrological hazards in small- and medium-scale catchments. The system collects data such as weather forecasts, precipitation measurements, water level gauges, discharge simulations and local observations of event-specific phenomena. In addition, IFKIS-Hydro incorporates a web-based information platform, which serves as a central hub for the submission and overview of data. Special emphasis is given to local information. This is accomplished particularly by human observers. In medium-scale catchments, discharge forecast models have an increasing importance in providing valuable information. IFKIS-Hydro was developed in several test regions in Switzerland and the first results of its application are available now. The system is constantly extended to additional regions and may become the standard for warning systems in smaller catchments in Switzerland.  相似文献   

Arsenic uptake by natural calcite: An XAS study     

F. Bardelli  P. Costagliola  F. Di Benedetto  P. Lattanzi  M. Romanelli 《Geochimica et cosmochimica acta》2011,75(11):3011-3023

As-bearing travertine rocks from Tuscany (Italy), where previous studies suggested the existence of a CO₃²⁻ ⇔ AsO₃³⁻ substitution in the calcite lattice, were investigated with X-ray Absorption Spectroscopy (XAS) at the As K-edge (11,867 eV). In two of the studied samples, XANES indicates that As is in the 5+ oxidation state only, and EXAFS analysis reveals a local environment typical of arsenate species. For these samples, the lack of detectable second shell signals suggests a poorly ordered environment, possibly corresponding to an adsorption onto oxide and/or silicate phases. On the other hand, in the third sample XANES reveals a mixed As oxidation state (III and V). This sample also presents evident next nearest neighbor coordination shells, attributed to As-Ca and As-As contributions. The occurrence of next neighbor shells is evidence that part of As is incorporated in an ordered lattice. Furthermore, the local structure revealed by EXAFS is compatible with As incorporation in the calcite phase, as further supported by DFT simulations. The observation of next neighbors shells only in the As(III)-rich sample suggests the substitution of the arsenite group in place of the carbonate one (CO₃²⁻ ⇔ AsO₃³⁻). The conclusion of this work is that uptake of As by calcite is in general less favored than adsorption onto iron oxhydroxides, but could become environmentally important wherever the latter phenomenon is hindered.  相似文献   

Toward a rapid probabilistic seismic vulnerability assessment using satellite and ground-based remote sensing   总被引：2，自引：1，他引：1  

Massimiliano Pittore  Marc Wieland 《Natural Hazards》2013,68(1):115-145

Natural hazards such as earthquakes threaten millions of people all around the world. In a few decades, most of these people will live in fast-growing, inter-connected urban environments. Assessing risk will, therefore, be an increasingly difficult task that will require new, multidisciplinary approaches to be tackled properly. We propose a novel approach based on different imaging technologies and a Bayesian information integration scheme to characterize exposure and vulnerability models, which are among the key components of seismic risk assessment.  相似文献   

The Holocene Secche di Lazzaro phreatomagmatic succession (Stromboli,Italy): evidence of pyroclastic density current origin deduced by facies analysis and AMS flow directions     

Guido Giordano  Massimiliano Porreca  Pietro Musacchio  Massimo Mattei 《Bulletin of Volcanology》2008,70(10):1221-1236

The edifice of Stromboli volcano gravitationally collapsed several times during its volcanic history (>100 ka–present). The largest Holocene event occurred during the final stage of the Neostromboli activity (∼13–5 ka), and was accompanied by the emplacement of phreatomagmatic and lahar deposits, known as the Secche di Lazzaro succession. A stratigraphic and paleomagnetic study of the Secche di Lazzaro deposits allows the interpretation of the emplacement and the eruptive processes. We identify three main units within the succession that correspond to changing eruption conditions. The lower unit (UA) consists of accretionary lapilli-rich, thinly bedded, parallel- to cross-stratified ash deposits, interpreted to indicate the early stages of the eruption and emplacement of dilute pyroclastic density currents. Upward, the second unit (UB) of the deposit is more massive and the beds thicker, indicating an increase in the sedimentation rate from pyroclastic density currents. The upper unit (UC) caps the succession with thick, immediately post-eruptive lahars, which reworked ash deposited on the volcano’s slope. Flow directions obtained by Anisotropy of Magnetic Susceptibility (AMS) analysis of the basal bed of UA at the type locality suggest a provenance of pyroclastic currents from the sea. This is interpreted to be related to the initial base-surges associated with water–magma interaction that occurred immediately after the lateral collapse, which wrapped around the shoulder of the sector collapse scar. Upward in the stratigraphy (upper beds of UA and UB) paleoflow directions change and show a provenance from the summit vent, probably related to the multiple collapses of a vertical, pulsatory eruptive column.  相似文献   

Lava flow hazard at Nyiragongo Volcano,DRC     

Giuseppe D. Chirico  Massimiliano Favalli  Paolo Papale  Enzo Boschi  Maria Teresa Pareschi  Arthur Mamou-Mani 《Bulletin of Volcanology》2009,71(4):375-387

Mt. Nyiragongo is one of the most dangerous volcanoes in the world for the risk associated with the propagation of lava flows. In 2002 several vents opened along a huge system of fractures, pouring out lava which reached and destroyed a considerable part of Goma, a town of about 500,000 inhabitants on the shore of Lake Kivu. In a companion paper (Favalli et al. in Bull Volcanol, this issue, 2008) we employed numerical simulations of probable lava flow paths to evaluate the lava flow hazard on the flanks of the volcano, including the neighbouring towns of Goma (DRC) and Gisenyi (Rwanda). In this paper we use numerical simulations to investigate the possibility of significantly reducing the lava flow hazard in the city through the construction of protective barriers. These barriers are added to the DEM of the area as additional morphological elements, and their effect is evaluated by repeating numerical simulations with and without the presence of barriers. A parametric study on barrier location, size, shape and orientation led to the identification of barriers which maximize protection while minimizing their impact. This study shows that the highest hazard area corresponding to eastern Goma, which was largely destroyed by lava flows in 2002, cannot be effectively protected from future lava flows towards Lake Kivu and should be abandoned. On the contrary, the rest of the town can be sheltered from lava flows by means of two barriers that deviate or contain the lava within the East Goma sector. A proposal for the future development of the town is formulated, whereby “new” Goma is completely safe from the arrival of lava flows originating from vents outside its boundaries. The proposal minimizes the risk of further destruction in town due to future lava flows.  相似文献   

Lava flow hazard at Nyiragongo volcano,D.R.C.     

Massimiliano Favalli  Giuseppe D. Chirico  Paolo Papale  Maria Teresa Pareschi  Enzo Boschi 《Bulletin of Volcanology》2009,71(4):363-374

The 2002 eruption of Nyiragongo volcano constitutes the most outstanding case ever of lava flow in a big town. It also represents one of the very rare cases of direct casualties from lava flows, which had high velocities of up to tens of kilometer per hour. As in the 1977 eruption, which is the only other eccentric eruption of the volcano in more than 100 years, lava flows were emitted from several vents along a N–S system of fractures extending for more than 10 km, from which they propagated mostly towards Lake Kivu and Goma, a town of about 500,000 inhabitants. We assessed the lava flow hazard on the entire volcano and in the towns of Goma (D.R.C.) and Gisenyi (Rwanda) through numerical simulations of probable lava flow paths. Lava flow paths are computed based on the steepest descent principle, modified by stochastically perturbing the topography to take into account the capability of lava flows to override topographic obstacles, fill topographic depressions, and spread over the topography. Code calibration and the definition of the expected lava flow length and vent opening probability distributions were done based on the 1977 and 2002 eruptions. The final lava flow hazard map shows that the eastern sector of Goma devastated in 2002 represents the area of highest hazard on the flanks of the volcano. The second highest hazard sector in Goma is the area of propagation of the western lava flow in 2002. The town of Gisenyi is subject to moderate to high hazard due to its proximity to the alignment of fractures active in 1977 and 2002. In a companion paper (Chirico et al., Bull Volcanol, in this issue, 2008) we use numerical simulations to investigate the possibility of reducing lava flow hazard through the construction of protective barriers, and formulate a proposal for the future development of the town of Goma.  相似文献   

人为因素导致的地面沉降   总被引：4，自引：0，他引：4  

Giuseppe GAMBOLATI Pietro TEATINI Massimiliano FERRONATO 《地学前缘》2006,13(1):160-178

天然气、石油、地下水、地热热水和卤水等流体运移出地下储存地层时,地层耗尽了流体而产生压缩变形,这些变形传递到地表表面就形成了人为的地面沉降。在本文中:(1)列举了世界上主要的地面沉降区域;(2)论述了引发地面沉降的力学机制,这些可以量测的地面沉降发生在地下含水层体系、天然气气田和石油油田之上;(3)描述了目前可以用于地面沉降测量和岩石变形原位测试的技术手段;(4)简要介绍了几个地面沉降预测的数值模型;(5)说明了用于控制地面沉降发展和减轻相关环境影响的几种防治措施。  相似文献   

Relict sand dredging for beach nourishment in the central Tyrrhenian Sea (Italy): effects on benthic assemblages     

Barbara La Porta  Monica Targusi  Loretta Lattanzi  Paola La Valle  Daniela Paganelli  & Luisa Nicoletti 《Marine Ecology》2009,30(S1):97-104

The aim of this study is to analyse the effects in space and time of relict sand-dredging activities on macrobenthic assemblages, in an area situated offshore Montalto di Castro (central Tyrrhenian Sea, Italy), and to analyse the recolonisation processes of macrobenthos in the dredged areas. The area in question is characterised by relict sand deposits (Holocenic paleo-beaches), used for beach nourishment along the Latium coast. The effects of sand extraction on benthic assemblages were investigated before, during and after three dredging operations. The sites analysed are located within the dredged areas (inside stations) and in neighbouring, not dredged, areas (outside stations). The results showed that the impact of sand extraction was confined to the dredged stations and to the areas in proximity to the dredged areas. During dredging activities, the structure of benthic assemblages within the impacted stations was characterised by low species richness and diversity. Both the direct removal of sediment and the re-suspension and consequent deposition of fine sediment affected benthic assemblages of the impacted stations. A few months after the dredgings, a recolonisation process was still observed at all the impacted stations. A gradual recolonisation process was observed at those stations affected by only one dredging, whereas a different recolonisation was observed at those stations affected by two dredgings over time. This study suggests that differences of re-colonisation processes of benthic assemblages are related to the intensity of dredging operations in terms of dredging frequency.  相似文献