The 1984 Abruzzo earthquake (Italy): an example of seismogenic process controlled by interaction between differently oriented synkinematic faults     

B. Pace  P. Boncio  G. Lavecchia 《Tectonophysics》2002,350(3)

The evolution of the seismogenic process associated with the M_s 5.8 Sangro Valley earthquake of May 1984 (Abruzzo, central Italy) is closely controlled by the Quaternary extensional tectonic pattern of the area. This pattern is characterised by normal faults mainly NNW striking, whose length is controlled by pre-existing Mio–Pliocene N100±10° left-lateral strike-slip fault zones. These are partly re-activated as right-lateral normal-oblique faults under the Quaternary extensional regime and behave as transfer faults.Integration of re-located aftershocks, focal mechanisms and structural features are used to explain the divergence between the alignment of aftershocks (WSW–ENE) and the direction of seismogenic fault planes defined by the focal mechanisms (NNW–SSE) of the main shock and of the largest aftershock (M_s=5.3).The faults that appear to be involved in the seismogenic process are the NNW–SSE Barrea fault and the E–W M. Greco fault. There is field evidence of finite Quaternary deformation indicating that the normal Barrea fault re-activates the M. Greco fault as right-lateral transfer fault. No surface faulting was observed during the seismic sequence. The apparently incongruent divergence between aftershocks and nodal planes may be explained by interpreting the M. Greco fault as a barrier to the propagation of earthquake rupturing. The rupture would have nucleated on the Barrea fault, migrating along-strike towards NNW. The sharp variation in direction from the Barrea to the M. Greco fault segments would have represented a structural complexity sufficient to halt the rupture and subsequent concentration of post-seismic deformation as aftershocks around the line of intersection between the two fault planes.Fault complexities, similar to those observed in the Sangro Valley, are common features of the seismic zone of the Apennines. We suggest that the zones of interaction between NW–SE and NNW–SSE Plio-Quaternary faults and nearly E–W transfer faults, extending for several kilometres in the same way as M. Greco does, might act as barriers to the along-strike propagation of rupture processes during normal faulting earthquakes. This might have strong implications on seismic hazard, especially for the extent of the maximum magnitude expected on active faults during single rupture episodes.  相似文献   

Image analysis and circular statistics for shape-fabric analysis: applications to lithified ignimbrites     

Bruno Capaccioni  Laura Valentini  Marco B. L. Rocchi  Giovanni Nappi  Damiano Sarocchi 《Bulletin of Volcanology》1997,58(7):501-514

 Computer-assisted image analysis can be successfully used to derive quantitative textural data on pyroclastic rock samples. This method provides a large number of different measurements such as grain size, particle shape and 2D orientation of particle main axes (directional- or shape-fabric) automatically and in a relatively short time. Orientation data reduction requires specific statistical tests, mainly devoted to defining the kind of particle distribution pattern, the possible occurrence of preferred particle orientation, the confidence interval of the mean direction and the degree of randomness with respect to pre-assigned theoretical frequency distributions. Data obtained from image analysis of seven lithified ignimbrite samples from the Vulsini Volcanic District (Central Italy) are used to test different statistics and to provide insight about directional fabrics. First, the possible occurrence of a significant deviation from a theoretical circular uniform distribution was evaluated by using the Rayleigh and Tukey χ ² tests. Then, the Kuiper test was performed to evaluate whether or not the observation fits with a unimodal, Von Mises-like theoretical frequency distribution. Finally, the confidence interval of mean direction was calculated. With the exception of one sample (FPD10), which showed a well-developed bimodality, all the analysed samples display significant anisotropic and unimodal distributions. The minimum number of measurements necessary to obtain reasonable variabilities of the calculated statistics and mean directions was evaluated by repeating random collections of the measured particles at increments of 100 particles for each sample. Although the observed variabilities depend largely on the pattern of distribution and an absolute minimum number cannot be stated, approximately 1500–2000 measurements are required in order to get meaningful mean directions for the analysed samples. Received: 9 April 1996 / Accepted: 26 December 1996  相似文献   

The Limit Problems for the Equation of Oscillations of a Satellite     

Alexander D. Bruno  Victor P. Varin 《Celestial Mechanics and Dynamical Astronomy》1997,67(1):1-40

We consider the ordinary differential equation of the second order, which describes oscillations of a satellite with respect to its mass center moving along an elliptic orbit with eccentricity e. The equation has two parameters: e and μ. It is regular for 0 ≤ e < 1 and singular when e = 1. For 1 we obtain three limit problems. Their bounded solution to the first limit problem form a two-dimensional (2D) continuous invariant set with a periodic structure. Solutions to the second limit problem form 2D and 3D manifolds. The μ-depending families of odd bounded solutions are singled out. One of the families is twisted into a self-similar spiral. To obtain the limit families of the periodic solutions to the original problem match together the odd bounded solutions to the first and the second limit problem. The point of conjunction is described by the third (the basic) limit problem. The limit families are very close to prelimit ones computed in earlier studies. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Great Western Australian iron ore boom     

Bruno Campana 《Mineralium Deposita》1967,1(4):322-322

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Near bottom variations of turbidity in the St Lawrence estuary     

Bruno d'Anglejan  R. Grant Ingram 《Estuarine, Coastal and Shelf Science》1984,19(6):655-672

Observations of the turbidity and velocity fields in the near-bottom waters of the St Lawrence estuary were obtained with a package which includes a self-recording attenuance meter and a currentmeter. The latter also measures salinity and temperature. Time series varying in length between 26 h and 26 days, and with repetition rates between one and 15 min are discussed for 3 typical open-channel and nearshore stations. A high-frequency sampling mode provides a means to observe the passage of a frontal disturbance over the bottom during the semi-diurnal cycle. With lower frequency records having lengths of one week to one month, contributions to the turbidity fluctuations due to the spring-neap oscillations, seasonal changes in run-off, and the sudden rise in solid discharge of local tributaries following storms, can be resolved. From turbidity polar diagrams, local onshore sources of particulate suspended matter can be identified. Among other advantages, it is possible from such records to time precisely the occurrence of turbidity peaks in relation to the ebb and flow velocities, to assess the importance of resuspension, and to specify exactly the time rate of change of the turbidity. On the whole, self-recording equipments provide a wealth of information unavailable from more traditional hydrocast sampling techniques.  相似文献   

Foldbelts with early salt withdrawal and diapirism: Physical model and examples from the northern Gulf of Mexico and the Flinders Ranges, Australia   总被引：1，自引：0，他引：1  

Mark G.  Bruno C.   《Marine and Petroleum Geology》2006,23(9-10):871-891

A physical experiment shows that shortening applied to existing diapirs and minibasins produces anomalous structural styles that are unlike those of more typical foldbelts. Strong minibasins remain largely undeformed while weak diapirs localize contractional strain. Short diapirs form the cores to folds and thrusted folds, whereas tall diapirs are squeezed and often welded, commonly leading to the extrusion of allochthonous material. Key features of the model are observed in real examples. In the northern Gulf of Mexico passive margin, minibasins were originally separated by a polygonal pattern of deep salt ridges, with diapirs located at ridge intersections. Gravity spreading resulted in squeezed diapirs (and associated allochthonous salt) connected by variably oriented contractional, extensional, and strike-slip structures. In the Flinders Ranges convergent-margin foldbelt of South Australia, preexisting diapirs were squeezed, welded, and thrusted, with anticlines plunging away in multiple directions, so that minibasins are surrounded by highly variable structures. A different geometry is observed in La Popa Basin, Mexico, where squeezing of a linear salt wall produced a vertical weld with diapirs at the terminations, rather than the culmination. In all areas, foldbelt geometries are strongly influenced by the preestablished salt-minibasin architecture.  相似文献   

Swathe seabed classification   总被引：2，自引：0，他引：2  

Pace  N.G. Gao  H. 《Oceanic Engineering, IEEE Journal of》1988,13(2):83-90

The degree to which different seabed types may be discriminated using features of the power spectrum of the signals backscattered from the seabed, in a side-scan mode, is evaluated. The statistics derived from the data samples considered suggest that the probability of correctly classifying the six seabed types (sand, mud, clay, gravel, stones, rock) is in excess of 97% using the spectral features that are defined  相似文献   

A review of current issues in air pollution modeling and simulation   总被引：1，自引：0，他引：1  

Bruno Sportisse 《Computational Geosciences》2007,11(2):159-181

Air pollution modeling is now a mature field, and comprehensive numerical models (the chemistry-transport models) are used in many applications. This article aims at reviewing the main issues from the point of view of applied mathematics and computational physics (as viewed by the author). We address topics such as subgrid parameterization, numerical algorithms with a focus on aerosol simulation, data assimilation and inverse modeling, reduction of high-dimensional models and propagation of uncertainties. Even if this article is strictly related to air pollution modeling, many issues and methods can be extended to dispersion of tracers in other media (for instance, water). This article is based on a plenary talk given at SIAM Geosciences, Avignon, June 2005.  相似文献   

Comparison of several BHT correction methods: a case study on an Australian data set     

Bruno Goutorbe  Francis Lucazeau  Alain Bonneville 《Geophysical Journal International》2007,170(2):913-922

Bottom-hole temperatures (BHT) from oil exploration provide useful constraints on the subsurface thermal regime, but they need to be corrected to obtain the equilibrium temperature. In this work, we introduce several BHT correction methods and compare them using a large Australian data set of more than 650 groups of multiple BHT measurements in about 300 oil exploration boreholes. Existing and suggested corrections are classified within a coherent framework, in which methods are divided into: line/cylinder source; instantaneous/continuous heat extraction; one/two component(s). Comparisons with reservoir test temperatures show that most of the corrections lead to reliable estimates of the formation equilibrium temperature within ±10 °C, but too few data exist to perform an intercomparison of the models based on this criterion. As expected, the Horner method diverges from its parent models for small elapsed times (or equivalently large radii). The mathematical expression of line source models suffers from an unphysical delay time that also restrains their domain of applicability. The model that takes into account the difference of thermal properties between circulating mud and surrounding rocks—that is the two-component model—is delicate to use because of its high complexity. For these reasons, our preferred correction methods are the cylindrical source models. We show that mud circulation time below 10 hr has a negligible effect. The cylindrical source models rely on one parameter depending on the thermal diffusivity and the borehole radius, which are poorly constrained, but the induced uncertainty on the extrapolations remains reasonably low.  相似文献   

Simulating the mobile barrier (MOSE) operation in the Venice Lagoon, Italy: global sea level rise and its implication for navigation     

Georg Umgiesser  Bruno Matticchio 《Ocean Dynamics》2006,56(3-4):320-332

Three years of mobile barrier operations have been simulated with a hydrodynamic model to check the efficiency of the barriers in defending the city of Venice from flooding. The simulations have been carried out in the actual situation and with a sea-level rise of 30 and 50 cm. Moreover, the interference of the barrier operations with the ship traffic has been studied. It is found that without a security increment for the forecasted water levels, the mobile barriers cannot defend completely Venice from flooding due to the uncertainty in the forecast. With a security increment of 10 cm, the barriers work well in actual conditions but still cannot avoid flooding with a global sea-level rise. The interference with the ship traffic is acceptable under actual conditions but becomes prohibitive with a sea-level rise of 50 cm, when nearly two-thirds of the ship passages are blocked or delayed.  相似文献