Extreme wave conditions in the tyrrhenian sea     

L. Cavaleri  P.L. De Filippi  G.F. Grancini  G.L. Iovenitti  R. Tosi 《Ocean Engineering》1986,13(2)

A hindcast study of extreme wave conditions in the Tyrrhenian Sea is described. The paper covers the different steps of the work, including the identification and the statistics of the weather patterns in the area, the choice of the storms to be hindcasted, the wind and wave models, a check of the best extremal distributions for the estimate of the extreme values probability, and the estimate of the accuracy of the final results. Detailed examples of the results are given, followed by a discussion of their reliability.  相似文献   

Seismological study of the central Ecuadorian margin: Evidence of upper plate deformation     

Nicole Bethoux  Monica Segovia  Viviana Alvarez  Jean-Yves Collot  Philippe Charvis  Audrey Gailler  Tony Monfret 《Journal of South American Earth Sciences》2011,31(1):139-152

A seismic study of a segment of the convergent margin of Ecuador is presented. During the SISTEUR campaign a network of 24 Ocean Bottom Seismometers (OBS) was deployed on the Carnegie Ridge, one line along the main axes of the ridge and two lines across the strike of the edge of the ridge, during one month. This marine network was complemented with a land network of 20 stations distributed in two lines: one parallel to the margin and the other perpendicular to it.The seismic event recorded by these networks, were located using different crustal models defined from the wide-angle seismic data modeling. Relative location techniques were used to improve earthquake locations. Seismogram waveform modeling allowed us to constrain hypocentral location for events farther than ～50 km from the network. This modeling also provided additional information to constrain the focal mechanisms of these events. The upper limit of the Interplate Seismogenic Zone (ISZ) is estimated to be at a 10 km depth in the region. The background seismic activity of the upper plate provided new insights:1) A seismic cluster that reaches the base of the overriding plate is linked to the Jipijapa-Portoviejo fault. The reactivation of this Quaternary fault is confirmed by focal mechanisms that provide rupture planes parallel to its superficial projection (N10°–N25°).2) The focal mechanisms presented in this study are compatible with a homogeneous regional stress field corresponding to an E–W to ESE–WNW compression and an NNE–SSW extension. The presence of strike-slip deformation, with a reverse component, corresponds to the NNE escape of the North Andean Block. Normal faulting accommodating this movement suggests that this part of the North Andean Block cannot be considered as a rigid block.  相似文献   

On the uniformity of anthropogenic Venice uplift     

Giuseppe Gambolati  Pietro Teatini  Massimiliano Ferronato  Tazio Strozzi  Luigi Tosi  Mario Putti 《地学学报》2009,21(6):467-473

A programme of Venice uplift because of seawater injection into a 600–800 m deep brackish aquifer underlying the lagoon has recently been advanced. As the actual spatial variability of the hydro‐geological parameters is to a large extent unknown, a controversial issue concerns the 25–30 cm heave prediction with the possible generation of differential displacements that might jeopardize the integrity of the architectural patrimony. It is shown that significant differential displacements have occurred in Venice in the past and are still presently occurring as evidenced by SAR interferometry. The results of a stochastic analysis addressing the variability of the hydraulic conductivity of the injected formation indicate that even a highly uneven aquifer expansion does not migrate to ground surface because of the smoothing effect exerted by the overburden. The predicted differential displacements are well below the values Venice is experiencing. Any a priori alarmism appears to be unfounded and unjustified.  相似文献   

A description of surface features in north Tyrrhena Terra, Mars: Evidence for extension and lava flooding     

Graziella Caprarelli  Monica Pondrelli  Lucia Marinangeli  Ronald Greeley 《Icarus》2007,191(2):524-544

We studied north Tyrrhena Terra, an approximately 39,000 km² area, located in the transition region straddling the Amenthes and Mare Tyrrhenum Mars Chart quadrangles 14 and 22, respectively. The study area comprises ancient terrains with infilled craters, ridges and valleys. Interpretation of orbiter data of ancient terrains is inherently difficult, but valuable information can be obtained using multiple datasets and analyzing various geological features. Using data from the High Resolution Stereo Camera on board Mars Express, complemented by Mars Global Surveyor MOLA DEM and MOC Narrow Angle datasets, we observed and interpreted surface morphologies at a scale suitable for geologic investigation. Morphometric examination of a 31 km diameter large impact crater indicated that tectonism and volcanism were responsible for its morphologic modification. Small impact crater depth/diameter relationships indicated that smooth surfaces of valleys are composed of highly consolidated material. Surface cracks and lobate fronts further suggested that the rocks are volcanic. Examination of tectonic features revealed that in the study area: a dominant NW-SE fabric is related to a ridge/bench-scarp-valley repetition consistent with synthetic and antithetic normal faulting; a NNW-SSE lineament represents the surface expression of normal faulting post-dating all other tectonic features. A weak NE-SW fabric is observable as small sublinear depressions, and at the contact between units internal to one large crater. One 20 km diameter crater in the study area was interpreted to be a caldera, infilled by thick volcanic rock layers. Identification of wrinkle ridges further indicated that thick layered lava flows infilled the main depressions of the study area. The available evidence suggests that the study area underwent multiple episodes of extension and volcanism.  相似文献   

Space–time correlation of earthquakes     

Patrizia Tosi  Valerio De Rubeis  Vittorio Loreto  Luciano Pietronero 《Geophysical Journal International》2008,173(3):932-941

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Clustering properties of Etna seismicity during 1981–1991     

M.S. Barbano  V. De Rubeis  P. Tosi  S. Vinciguerra 《Journal of Seismology》2000,4(2):191-196

Space and time clustering properties ofseismic activity, affecting Etna Volcano (Italy)during 1981–1991, are investigated by fractaldimension analysis. Very interesting volcanic andseismic activity occurred within this time interval.Temporal evolution of the time fractal dimension D _t calculated on a moving window, revealscorrelation with the eruptive processes at differenttime scales confirming results obtained for a differenttime span (De Rubeis et al., 1997). Spatial fractaldimension D _s shows to be negativelycorrelated with the time fractal dimension D _t, suggesting a peculiar dynamic patternassociated with volcanic processes.  相似文献   

Methods applied in studies of benthic marine debris     

Spengler A  Costa MF 《Marine pollution bulletin》2008,56(2):226-230

The ocean floor is one of the main accumulation sites of marine debris. The study of this kind of debris still lags behind that of shorelines. It is necessary to identify the methods used to evaluate this debris and how the results are presented and interpreted. From the available literature on benthic marine debris (26 studies), six sampling methods were registered: bottom trawl net, sonar, submersible, snorkeling, scuba diving and manta tow. The most frequent method used was bottom trawl net, followed by the three methods of diving. The majority of the debris was classified according to their former use and the results usually expressed as items per unity of area. To facilitate comparisons of the contamination levels among sites and regions some standardization requirements are suggested.  相似文献   

Geochemical characteristics of phosphorus in surface sediments of two major Chinese mariculture areas: The Laizhou Bay and the coastal waters of the Zhangzi Island     

Wen Zhuang  Xuelu Gao  Yong Zhang  Qianguo Xing  Luigi Tosi  Song Qin 《Marine pollution bulletin》2014

Phosphorus (P) in surface sediments of the Laizhou Bay (LB) and the coastal waters around the Zhangzi Island (ZI) was analyzed. Six forms of P were separated — exchangeable or loosely sorbed P (Ads–P), aluminum-bound P (Al–P), iron-bound P (Fe–P), authigenic apatite plus CaCO₃-bound P plus biogenic apatite (Ca–P), detrital apatite plus other inorganic P (De–P) and organic P (OP). The average contents of P in the LB were in the order: De–P > OP > Ca–P > Fe–P > Ads–P > Al–P; in the ZI, the corresponding order was De–P > OP > Fe–P > Ca–P > Ads–P > Al–P. Due to the high nutrient loadings from the surrounding rivers, TP contents in sediments of the LB were higher than in those of the ZI. The potential bio-available P (Ads–P and OP) accounted for 14.7% and 24.2% of TP in sediments of the LB and the ZI, respectively.  相似文献   

Constraining pre-eruptive magma conditions and unrest timescales during the Monte Nuovo eruption (1538 ad; Campi Flegrei,Southern Italy): integrating textural and CSD results from experimental and natural trachy-phonolites     

Fabio Arzilli  Monica Piochi  Angela Mormone  Claudia Agostini  Michael R. Carroll 《Bulletin of Volcanology》2016,78(10):72

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A technique to test finite difference schemes to model some geophysical processes in a geological structure     

Giansilvio Ponzini  Nicola Tosi 《Mathematical Geology》1992,24(5):499-537

A preliminary problem to solve in the set-up of a mathematical model simulating a geophysical process is the choice of a suitable discrete scheme to approximate the governing differential equations. This paper presents a simple technique to test finite difference schemes used in the modeling of geophysical processes occurring in a geological structure. This technique consists in generating analytical solutions similar to the ones characterizing a geophysical process, given general information on some relevant parameters. Useful information for the choice of the discrete scheme to employ in the mathematical model simulating the original geophysical process can be obtained from the comparison between the analytical solution and the approximated numerical solutions generated by means of different discrete schemes. Two classes of numerical examples approximating the differential equation that governs the steady state earth's heat flow have been treated using three different finite differences schemes. The first class of examples deals with media whose phenomenological parameters vary as continuous space functions; the second class, instead, deals with media whose phenomenological parameters vary as discontinuous space functions. The finite difference schemes that have been utilized are: Centered Finite Difference Scheme (CDS), Arithmetic Mean Scheme (AMS), and Harmonic Mean Scheme (HMS).The numerical simulations showed that: the CDS may yield physically inconsistent solutions if the lattice internodal distance is too large, but in case of phenomenological parameters varying as a continuous function, this pitfall can be avoided increasing the lattice node refinement. In case of phenomenological parameters varying as a discontinuous function, instead, the CDS may yield physically inconsistent solutions for any lattice-node refinement. The HMS produced good results for both classes of examples showing to be a scheme suitable to model situations like these.  相似文献