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   

2009年意大利中部阿奎拉地震DInSAR同震位移的有限断层反演     

S·Atzori  I·Hunstad  M·Chini  S·Salvi  C·Tolomei  C·Bignami  S·Stramondo  E·Trasatti  A·Antonioli  E·Boschi  李晶 《世界地震译丛》2009,(4):30-36

根据环境卫星Envisat和COSMO—SkyMed模型（为同震位错研究而首次设计的X波段反演干涉图）的DInSAR干涉图,确定了2009年4月6日阿奎拉Mw=6．3级地震时激发的断层几何形状及运动特征。我们的主震最佳拟合解为一个约16km长、12km宽的正断层,存在小的右旋分量,向西南倾斜47°,最大滑动约90cm。虽然地震位错可能只有1km深,但是断层面的上倾投影与标绘的帕加尼卡-南德米特里奥断层的北段相符合,在现场观察到了该断层地表破裂的迹线。该断层在现有震源目录中的缺失表明,需要对具体的地表和地下进行进一步的地质和地球物理勘测,以便对局部规模的地震危险性做出更准确的评估。  相似文献   

Isotopic and element exchange during serpentinization and metasomatism at the Atlantis Massif (MAR 30°N): Insights from B and Sr isotope data     

Chiara Boschi  Andrea Dini  Deborah S. Kelley 《Geochimica et cosmochimica acta》2008,72(7):1801-1823

The Lost City hydrothermal system at the southern Atlantis Massif (Mid-Atlantic Ridge, 30°N) provides a natural laboratory for studying serpentinization processes, the temporal evolution of ultramafic-hosted hydrothermal systems, and alteration conditions during formation and emplacement of an oceanic core complex. Here we present B, O, and Sr isotope data to investigate fluid/rock interaction and mass transfer during detachment faulting and exhumation of lithospheric sequences within the Atlantis Massif. Our data indicate that extensive serpentinization was a seawater-dominated process that occurred predominately at temperatures of 150-250 °C and at high integrated W/R ratios that led to a marked boron enrichment (34-91 ppm). Boron removal from seawater during serpentinization is positively correlated with changes in δ¹¹B (11-16‰) but shows no correlation with O-isotope composition. Modeling indicates that B concentrations and isotope values of the serpentinites are controlled by transient temperature-pH conditions. In contrast to prior studies, we conclude that low-temperature marine weathering processes are insignificant for boron geochemistry of the Atlantis Massif serpentinites. Talc- and amphibole-rich fault rocks formed within a zone of detachment faulting at temperatures of approximately 270-350 °C and at low W/R ratios. Talc formation in ultramafic domains in the massif was subsequent to an early stage of serpentinization and was controlled by the access of Si-rich fluids derived through seawater-gabbro interactions. Replacement of serpentine by talc resulted in boron loss and significant lowering of δ¹¹B values (9-10‰), which we model as the product of progressive extraction of boron. Our study provides new constraints on the boron geochemical cycle at oceanic spreading ridges and suggests that serpentinization associated with ultramafic-hosted hydrothermal systems may have important implications for the behavior of boron in subduction zone settings.  相似文献   

Investigating fossil hydrothermal systems by means of fluid inclusions and stable isotopes in banded travertine: an example from Castelnuovo dell’Abate (southern Tuscany,Italy)     

Valentina Rimondi  Pilario Costagliola  Giovanni Ruggieri  Marco Benvenuti  Chiara Boschi  Andrea Brogi  Enrico Capezzuoli  Guia Morelli  Massimo Gasparon  Domenico Liotta 《International Journal of Earth Sciences》2016,105(2):659-679

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The micrometeorite flux to Earth during the earliest Paleogene reconstructed in the Bottaccione section (Umbrian Apennines), Italy     

Samuele Boschi  Birger Schmitz  Ellinor Martin  Fredrik Terfelt 《Meteoritics & planetary science》2020,55(7):1615-1628

Based on sediment‐dispersed extraterrestrial spinel grains in the Bottaccione limestone section in Italy, we reconstructed the micrometeorite flux to Earth during the early Paleocene. From a total of 843 kg of limestone, 86 extraterrestrial spinel grains (12 grains > 63 μm, and 74 in the 32–63 μm fraction) have been recovered. Our results indicate that the micrometeorite flux was not elevated during the early Paleocene. Ordinary chondrites dominated over achondritic meteorites similar to the recent flux, but H chondrites dominated over L and LL chondrites (69%, 22%, and 9%, respectively). This H‐chondrite dominance is similar to that recorded within an enigmatic ³He anomaly (70, 27, and 3%) in the Turonian, but different from just before this ³He anomaly and in the early Cretaceous, where ratios are similar to the recent flux (~45%, 45%, and 10%). The K‐Ar isotopic ages of recently fallen H chondrites indicate a small impact event on the H‐chondrite parent body ~50 to 100 Ma ago. We tentatively suggest that this event is recorded by the Turonian ³He anomaly, resulting in an H‐chondrite dominance up to the Paleocene. Our sample spanning the 20 cm above the Cretaceous–Paleogene (K–Pg) boundary did not yield any spinel grains related to the K–Pg boundary impactor.  相似文献   

Stock structure and demographic history of the Indo-West Pacific mud crab Scylla serrata     

Sara Fratini  Lapo Ragionieri  Stefano Cannicci 《Estuarine, Coastal and Shelf Science》2010

The increasing exploitation of mangrove forests, without any sustainable planning, has been seriously compromising the survival of this ecosystem and of its exclusive resources. Scylla serrata is one of the most commercially exploited crabs inhabiting mangroves and estuaries of the Indo-Pacific region. This species is extensively harvested, mainly for selling to the tourist market, and, as a consequence, its populations are in constant decline. The aim of the present study was to assess the level of genetic exchange of S. serrata within the Western Indian Ocean (WIO), using a population genetic structure approach. To achieve this goal, we reconstructed the intra-specific geographic pattern of genetic variation by partial sequencing the mitochondrial DNA cytochrome oxidase subunit I, in samples from seven mangrove sites of the WIO. Our data set then encompassed all the sequences for the same genetic marker deposited in Genbank and corresponding to samples from South East Asia, Australia and some Pacific Islands: this allowed us to estimate the level of connectivity among S. serrata populations within its distribution area.  相似文献   

Equations of state for silicates in the metallic form     

E. Boschi  M. Caputo 《Pure and Applied Geophysics》1972,101(1):5-9

Summary We re-examine the problem of the mantle-core discontinuity. By means of theoretical equations of state for silicates in the metallic form, we conclude, once more, that it is a composition discontinuity rather than a phase transition.

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Sommario Si riesamina il problema della discontinuità tra il mantello ed il nucleo. Per mezzo di equazioni di stato teoriche si conclude che essa non può essere una transizione di fase.

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Linear or non-linear rheology in the Earth's mantle: the prevalence of power-law creep in the postglacial isostatic readjustment of Laurentia   总被引：1，自引：0，他引：1  

Paolo Gasperini  Giulio Dal Forno  Enzo Boschi 《Geophysical Journal International》2004,157(3):1297-1302

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Spectroscopic survey of the Galaxy with Gaia– II. The expected science yield from the Radial Velocity Spectrometer     

M. I. Wilkinson  A. Vallenari  C. Turon  U. Munari  D. Katz  G. Bono  M. Cropper  A. Helmi  N. Robichon  F. Thévenin  S. Vidrih  T. Zwitter  F. Arenou  M.-O. Baylac  G. Bertelli  A. Bijaoui  F. Boschi  F. Castelli  F. Crifo  M. David  A. Gomboc  A. Gómez  M. Haywood  U. Jauregi  P. de Laverny  Y. Lebreton  P. Marrese  T. Marsh  S. Mignot  D. Morin  S. Pasetto  M. Perryman  A. Pr&#;a  A. Recio-Blanco  F. Royer  A. Sellier  A. Siviero  R. Sordo  C. Soubiran  L. Tomasella  Y. Viala 《Monthly notices of the Royal Astronomical Society》2005,359(4):1306-1335

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