Rupture Process of the 1995 Antofagasta Subduction Earthquake (Mw = 8.1)     

D. L. Carlo  T. Lay  C. J. Ammon  J. Zhang 《Pure and Applied Geophysics》1999,154(3-4):677-708

—A finite-source rupture model of the July 30, 1995, M _w = 8.1 Antofagasta (Northern Chile) subduction earthquake is developed using body and surface waves that span periods from 20 to 290s. A long-period (150–290s) surface-wave spectral inversion technique is applied to estimate the average finite-fault source properties. Deconvolutions of broadband body waves using theoretical Green’s functions, and deconvolutions of broadband fundamental mode surface waves using empirical Green’s functions provided by a large aftershock, yield effective source time functions containing periods from 20 to 200s for many directivity parameters. The source time functions are used in an inverse radon transform to image a one-dimensional spatial model of the moment rate history. The event produced a predominantly unilateral southward rupture, yielding strong directivity effects on all seismic waves with periods less than a few hundred seconds. The aftershock information, spectral analysis, and moment rate distribution indicate a rupture length of 180–200km, with the largest slip concentrated in the first 120km, a rupture azimuth of 205°± 10° along the Chilean coastline, and a rupture duration of 60–68s with a corresponding average rupture velocity of 3.0–3.2km/s. The overall rupture character is quite smooth, accentuating the directivity effects and reducing the shaking intensity, however there are three regions with enhanced moment rate distributed along the rupture zone near the epicenter, 50 to 80km south of the epicenter, and 110 to 140km south of the epicenter.  相似文献   

The Cengio submarine turbidite system of the Tertiary Piedmont Basin, Northwestern Italy     

Carlo Cazzola  Emiliano Mutti  Bartolomeo Vigna 《Geo-Marine Letters》1984,3(2-4):173-177

The Cengio sandstone member of the Tertiary Piedmont Basin in northwestern Italy has a conservatively estimated volume of 2.5 to 3 km³ (length: 6.4 km; width: 4.8 km; thickness: 170 m). It is interpreted as a sandstone-rich submarine fan deposit. The Cengio member consists of eight tabular depositional sandstone lobes that are 5- to 25-m thick. These lobes filled a submarine structural depression and onlap and/or pinch-out against bounding slope mudstones. The stacking of the lobe units was related to synsedimentary tectonism. Margin setting represents fan and/or source area  相似文献   

The 1983 Mount Etna eruption: thermochemical and dynamical inferences     

Raffaello Trigila  Frank J. Spera  Carlo Aurisicchio 《Contributions to Mineralogy and Petrology》1990,104(5):594-608

Thermochemical calculations and laboratory phase equilibration experiments on lavas of the 131 day 1983 Mt. Etna flank eruption of 0.1 km³ were undertaken to investigate possible systematic variations in inferred melt-phenocryst equilibration conditions as a function of time. The 1983 Mt. Etna lavas are multiply saturated; plagioclase, clinopyroxene and olivine, the dominant phenocrysts, occur in the ratio 1:1/2:1/4. Melts (glasses) plot close to the plagioclase saturated olivine-clinopyroxene low pressure cotectic on a Walker-O'Hara diopside-forsterite-silica diagram suggesting equilibration of melt and phenocrysts in a high level magma reservoir. Total pressures, temperatures and dissolved H₂O concentrations were calculated using the isoactivity method of Carmichael and coworkers based on about 300 elelctron microprobe analyses of coexisting olivine, clinopyroxene and plagioclase phenocrysts, microphenocrysts and groundmass microlites for samples collected 6, 46 and 125 days after the start of the eruption. Total pressures (P _t), temperatures and H₂O contents based on representative olivine-clinopyroxene pairs are 140 MPa, 1105°C, 2.4 wt% H₂O; 255 MPA, 1112°C, 1.0 wt% H₂O and 85 MPa, 1096°C, 1.8 wt% H₂O respectively for the early (283), middle (I83) and late (L83) samples. Corresponding equilibration depths are in the range 3 to 10 kilometers. Plagioclase feldspar phenocrysts, while showing more evidence of disequilibrium, provide compatible estimates of P _t and T when analysis is restricted to the low anorthite mode of the plagioclase frequency-composition histograms: 133 MPa and 1115°C; 260 MPa and 1117°C and 103 MPa and 1104°C, repectively for 283, I83 and L83. The pre-eruptive (i.e., in situ) temperature-pressure gradient calculated from olivine-clinopyroxene equilibria is 10.6 K/kbar. This compares well with independent estimates of the temperature-pressure derivative of the (pseudo) invariant point composition (10 to 12 K/kbar) in both model (e.g., diopside-forsterite-anorthite, Presnall et al. 1978) and natural (e.g., Walker et al. 1979; Grove et al. 1982) systems. Apparently, magma within the Etna reservoir was in a quasiequilibrium state buffered by its multiply-saturated character immediately preceding eruption. The temporal variation of computed P _t, T and H₂O concentrations for melt-phenocryst equilibrium agrees well with predictions based on simulations of the withdrawal of magma from a body zoned with respect to dissolved H₂O provided the temporal record of magma discharge is taken into account. Discharge varied by a factor of about 100 during the sample collection interval. The intermediate P _t but high H₂O content inferred for sample 283 reflects the withdrawal of H₂O enriched magma during an early phase of high average discharge of about (350 m³/s) before evaculation isochrons became quasistationary. The high P _t and relatively dry I83 magma reflects the deepening of the evacuation isochrons after 50 days of intermediate discharge with the development of quasi-stationary isochrons in time and space. Sample L83 from day 125 near the end of the eruption reflects the shoaling of evacuation isochrons (hence low P _t and relatively high H₂O content) associated with the observed low (0.5 m³/s) discharge. Our results show that thermochemical modeling efforts provide important opportunities for testing the predictions of magma with-drawal simulations.  相似文献   

Natural and Anthropic Middle-term Variations in the Delta System at the Mouth of the Goro River (Po Delta, Italy)     

Carlo Del Grande  Giovanni Gabbianelli  Umberto Simeoni 《Marine Ecology》2002,23(S1):169-183

Abstract. The modern delta system of the Po River is the result of an evolution strictly controlled by anthropic factors and mainly developed during a period of climatic deterioration (Little Ice Age 1550/1850).
At the beginning of the 17^th century the main branch of the Po River, Fornaci Po, was modified with the "Cut of Viro" in order to avoid landfill of the Venetian Lagoon. Simultaneously, the southernmost branch of Ariano, or Goro, was forced to flow southwards. Subsequent sedimentary variations, caused by changes in the climatic conditions, contributed to make the area supplied by the Goro Po River increasingly lagoonary. In the second half of the 19^th century (end of the Little Ice Age – L.I.A. –), the first coastal spits started to take shape and developed in different systems throughout the entire following century. Coastal spits turned out to produce in the original bay, a progressive closure towards the sea. The strong decrease in solid loads, characterising the second half of the 20^th century and mainly due to anthropic factors, marks the beginning of a new phase extending to the overall Po Delta system, in which the mouth layout is controlled by wave energy.  相似文献   

How friends share urban space: An exploratory spatiotemporal analysis using mobile phone data   总被引：1，自引：0，他引：1       下载免费PDF全文

Yang Xu  Alexander Belyi  Iva Bojic  Carlo Ratti 《Transactions in GIS》2017,21(3):468-487

This study proposes a framework to investigate the roles of urban spaces in connecting social contacts (i.e., “friends”). The framework is applied to a Call Detail Record (CDR) dataset collected in Singapore. First, a comparative analysis is performed to understand how friends share urban space differently from random people. Then, we derive two metrics to quantify the “bonding” and “bridging” capabilities of places in the city. The two metrics reflect the potential of a place in connecting friends and random people (e.g., chance encounters), respectively. Finally, we examine the temporal signature of the places’ bonding capabilities, and associate the results with various types of Points of Interest (POIs). We find that: (1) friends are more likely to share urban space than random people, and they also share more locations; (2) a place could play different roles in connecting friends vs. random people, and the relationship (between bonding and bridging) varies depending on the time and type of a day (weekdays vs. weekends); (3) the temporal signature of bonding capability is strongly related to the semantics of a place; (4) certain POI types (e.g., shopping malls) tend to have a much higher impact on bonding capability than others (e.g., sports centers).  相似文献   

Modeling flood event characteristics using D-vine structures   总被引：1，自引：0，他引：1  

Maryam?ShafaeiEmail author  Ahmad?Fakheri-Fard  Yagob?Dinpashoh  Rasoul?Mirabbasi  Carlo?De Michele 《Theoretical and Applied Climatology》2017,130(3-4):713-724

The authors investigate the use of drawable (D-)vine structures to model the dependences existing among the main characteristics of a flood event, i.e., flood volume, flood peak, duration, and peak time. Firstly, different three- and four-dimensional probability distributions were built considering all the permutations of the conditioning variables. The Frank copula was used to model the dependence of each pair of variables. Then, the appropriate D-vine structures were selected using information criteria and a goodness-of-fit test. The influence of varying the data length on the selected D-vine structure was also investigated. Finally, flood event characteristics were simulated using the four-dimensional D-vine structure.  相似文献   

Variations of trace elements and rare earth elements (REEs) treated by two different methods for snow-pit samples on the Qinghai-Tibetan Plateau and their implications     

YueFang Li  Zhen Li  Ju Huang  Giulio Cozzi  Clara Turett  Carlo Barbante  LongFei Xiong 《寒旱区科学》2017,9(6):568-579

Although previous investigations of the trace elements in snow and ice from the Qinghai-Tibetan Plateau obtained interesting information about pollution from human activities on the plateau, most were based on traditional acidification methods. To emphasize the influence of the different sample-preparation methods on the records of trace elements and rare earth elements, snow samples were collected from glaciers on the Qinghai-Tibetan Plateau in China and prepared using two methods: traditional acidification and total digestion. Concentrations of 18 trace elements (Al, Ti, Fe, Rb, Sr, Ba, V, Cr, Mn, Li, Cu, Co, Mo, Cs, Sb, Pb, Tl, and U), along with 14 rare earth elements (REEs: La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu), Y, and Th in the snow samples, were measured using inductively coupled plasma-sector field mass spectrometry (ICP-SFMS). The results showed that the mass fraction of the trace elements (defined as ratio of concentration in the acid-leachable fraction to that in the digested sample) such as Mo, Ti, Al, Rb, and V, varied from 0.06 to 0.5. The mass fraction of other trace elements varied from about 0.6 to more than 0.9; those of the REEs, Y, and Th varied from 0.34 to 0.75. Lower mass fractions will lead to an overestimated contribution of other sources, especially human activities, and the underestimated fluxes of these trace elements (especially REEs, Y, and Th, as well as dust) if the REEs are used as the proxy for the crust dust. The two sample-preparation methods exhibited different REE normalized distribution patterns, REE ratios, and provenance-tracing results. The REE normalized distribution patterns and proxies in the digested samples are more reliable and integrated than those found in traditional acidification method for dust-provenance tracing.  相似文献   

Can Rock Composition Affect Sublittoral Epibenthic Communities?     

Riccardo Cattaneo-Vietti  Giancarlo Albertelli  Giorgio Bavestrello  Carlo Nike Bianchi  Carlo Cerrano  Mariachiara Chiantore  Laura Gaggero  Carla Morri  Stefano Schiaparelli 《Marine Ecology》2002,23(S1):65-77

Abstract. Biomineralogy, as the complex of interactions at different levels (cell, organism, species, and community) between organisms and minerals, may play a significant role in the spatial distribution and structure of marine communities. For instance, a negative influence of quartz has been underlined on the Mediterranean benthic communities, which show a species-poorer structure in quartz-rich environments. Excluding the role of quartz, the aim of this work is to verify whether the composition of various mineralogical substrata can affect a hard-bottom benthic community. In the Ligurian Sea, the Levanto area shows an astonishing complex of substrata with different petrographic characters: in a few kilometres, sandstones, serpentinites, gabbros, and basalts occur in geometric association. Consequently, this area represents a suitable frame for this type of study. Herein, algal photophilic assemblages growing on the four mineralogical substrata show significant differences in number of species and percentage cover or abundance. This suggests a significant influence of rock mineral composition on the hard bottom community. Therefore, rock composition must be taken into account for a better understanding of the processes at the basis of hard-bottom community development and diversity.  相似文献   

Sull'utilizzabilità a scopo geofisico delle relazioni fra anomalie Eötvössiane e magnetiche     

Prof. Dr. Carlo Morelli 《Pure and Applied Geophysics》1950,18(1):143-147

Riassunto Viene mostrato come sia possibile dare pratiche applicazioni alle formule diEötvös sulle relazioni fra anomalie gravimetriche e magnetiche, in modo da ricavare le proprietà magnetiche delle rocce che causano l'anomalia. Da ciò l'opportunità di eseguire sempre unitamente a misurazioni con la bilancia di torsione anche misure magnetiche.

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Summary It is shown how is possible to give pratical applications toEötvös' formulas on relations between gravitational and magnetic anomalies, in such a way as to obtain informations on magnetic properties of rocks that cause the anomaly. It follows the opportunity of executing together with torsion balance measures, in as much as possible, also magnetic measurements.

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Trasformazioni con mezzi ottico-meccanici fra le proiezioni cartografiche della sfera     

Dr. Carlo Bernasconi 《Pure and Applied Geophysics》1949,15(3-4):227-235

Riassunto I. Premesso che l'analizzatore differenziale diBush è adattabile alla costruzione di funzioni di due variabili, si studiano alcuni strumenti che, applicati all'analizzatore, permettono di eseguire varie transformazioni fra le proiezioni cartografiche della sfera, espresse in forma esplicita. In particolare si esaminano le transformazioni fra le proiezioni cilindriche e coniche. — II. Rilevati gliinconvenienti che comporta l'impiego di soli mezzi meccanici, si introducono dispositivi ottico-meccanici che restringono il campo delle transformazioni, ma le rendono, praticamente effettuabili. Detti dispositivi vengono applicati, oltre alle transformazioni citate, anche per ottenere la equivalente sinusoidale a paralleli rettilinei e circolari.

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Summary I. The Differential Analyser ofBush, being fit for the construction of two variables functions, some instruments are studied which, applied to the Analyser, allow several transformations between cartographic projections of the sphere, expressed in explicit form, to be executed. Particularly, transformations between cylindrical and conical projections are examined. — II. After having revealed the failures produced by the use of mechanical means only, optic-mechanical devices are introduced, which restrain the range of transformations but make them practically effectible. Such devices are applied, besides the previous transformations, also to obtain the sinusoidal equivalent in rectilinear and circular parallels.

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