Moment magnitude (Mw) from hydrophone records of low energy volcanic quakes     

Guardato  Sergio  Donnarumma  Gian Paolo  Riccio  Rosario  Del Pezzo  Edoardo  Iannaccone  Giovanni 《Journal of Seismology》2022,26(5):875-882

Earthquake magnitude calibration using hydrophone records has been carried out at Campi Flegrei caldera, an active area close to the highly populated area of Naples city, partly undersea. Definite integrals of the hydrophone records amplitude spectra, between the limits of 1 and 20 Hz, were calculated on a set of small volcano-tectonic earthquakes with moment magnitudes ranging from 1 to 3.3. The coefficients of a linear relationship between the logarithm of these integrals and the magnitude were obtained by linear optimization, thus defining a useful equation to calculate the moment magnitude from the hydrophone record spectra. This method could be easily exported to other volcanic areas, where submerged volcanoes are monitored by networks of hydrophones and seismic sensors on land. The proposed approach allows indeed magnitude measurements of small magnitude earthquakes occurring at sea, thus adding useful information to the seismicity of these volcanoes.

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Flash flood occurrence and magnitude assessment in an alluvial fan context: the October 2011 event in the Southern Apennines     

Santo  Antonio  Santangelo  Nicoletta  Di Crescenzo  Giuseppe  Scorpio  Vittoria  De Falco  Melania  Chirico  Giovanni Battista 《Natural Hazards》2015,78(1):417-442

Natural Hazards - This study presents the analysis of flash floods triggered by an extreme rainfall event that occurred on 7 October, 2011, over the Marzano carbonate massif (Southern Apennines)....  相似文献   

Gravitational mode calculation of basins discretized by orthogonal curvilinear grids     

Gian Mario BeltramiRiccardo Briganti 《Ocean Engineering》2003,30(7):833-853

This paper presents a simple and straightforward method for carrying out the direct numerical solution of the eigenvalue problem associated to the homogeneous linear shallow-water equations expressed using orthogonal curvilinear coordinates, when ‘adiabatic’ boundary conditions apply. These equations, together with the boundary conditions, define a self-adjoint problem in the continuum. The method presented here, which is thought for calculating the 2-D theoretical gravity modes of both natural and artificial basins, relies on a change of basis of the dependent variable vector. This preliminary transformation makes it, in fact, possible to formulate two different numerical approaches which guarantee the self-adjoint property of the discrete form of the system consisting of the governing equations and the boundary conditions. The method is tested using a square and a fully circular domain, both of which allow comparisons with well-known analytical and numerical solutions. Discretizing the physical domain of a fully circular basin by a cylindrical coordinate grid makes it possible to show the actual efficiency of the method in calculating the theoretical gravity modes of basins discretized by a boundary-following coordinate grid which allows laterally variable resolution.  相似文献   

Role of Extratropical Cyclones in the Recently Observed Increase in Poleward Moisture Transport into the Arctic Ocean     

Gian A.VILLAMIL-OTERO  Jing ZHANG  Juanxiong HE  Xiangdong ZHANG 《大气科学进展》2018,35(1):85-94

Poleward atmospheric moisture transport(AMT) into the Arctic Ocean can change atmospheric moisture or water vapor content and cause cloud formation and redistribution, which may change downward longwave radiation and, in turn, surface energy budgets, air temperatures, and sea-ice production and melt. In this study, we found a consistently enhanced poleward AMT across 60?N since 1959 based on the NCAR–NCEP reanalysis. Regional analysis demonstrates that the poleward AMT predominantly occurs over the North Atlantic and North Pacific regions, contributing about 57% and 32%, respectively, to the total transport. To improve our understanding of the driving force for this enhanced poleward AMT, we explored the role that extratropical cyclone activity may play. Climatologically, about 207 extratropical cyclones move across 60?N into the Arctic Ocean each year, among which about 66(32% of the total) and 47(23%) originate from the North Atlantic and North Pacific Ocean, respectively. When analyzing the linear trends of the time series constructed by using a 20-year running window, we found a positive correlation of 0.70 between poleward yearly AMT and the integrated cyclone activity index(measurement of cyclone intensity, number, and duration). This shows the consistent multidecadal changes between these two parameters and may suggest cyclone activity plays a driving role in the enhanced poleward AMT. Furthermore, a composite analysis indicates that intensification and poleward extension of the Icelandic low and accompanying strengthened cyclone activity play an important role in enhancing poleward AMT over the North Atlantic region.  相似文献   

Design of passive systems for control of inelastic structures     

Gian Paolo Cimellaro  Oren Lavan  Andrei M. Reinhorn 《地震工程与结构动力学》2009,38(6):783-804

A design strategy for control of buildings experiencing inelastic deformations during seismic response is formulated. The strategy is using weakened, and/or softened, elements in a structural system while adding passive energy dissipation devices (e.g. viscous fluid devices, etc.) in order to control simultaneously accelerations and deformations response during seismic events. A design methodology is developed to determine the locations and the magnitude of weakening and/or softening of structural elements and the added damping while insuring structural stability. A two‐stage design procedure is suggested: (i) first using a nonlinear active control algorithm, to determine the new structural parameters while insuring stability, then (ii) determine the properties of equivalent structural parameters of passive system, which can be implemented by removing or weakening some structural elements, or connections, and by addition of energy dissipation systems. Passive dampers and weakened elements are designed using an optimization algorithm to obtain a response as close as possible to an actively controlled system. A case study of a five‐story building subjected to El Centro ground motion, as well as to an ensemble of simulated ground motions, is presented to illustrate the procedure. The results show that following the design strategy, a control of both peak inter‐story drifts and total accelerations can be obtained. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

Bed morphology and generation of step–pool channels     

Roman B. Weichert  Gian Reto Bezzola  Hans‐Erwin Minor 《地球表面变化过程与地形》2008,33(11):1678-1692

Flume experiments have been carried out to study the formation processes and the bed morphology of step–pool channels. From the experiments different step types and step configurations could be distinguished depending on the stream power. These step types can be seen as an image of the generation mechanisms of step–pool systems. These results suggest that the bed roughness geometry develops towards a condition that provides the maximum possible bed stability for a given grain size distribution. In contrast to a variety of other studies, antidunes did not contribute to the generation of the step structures. However, the data of the presented study fits well into the region of antidune formation proposed by Kennedy for sand‐bed rivers. This observation points out that step–pool field‐data located in the Kennedy region do not inevitably prove that antidunes played a role in step development. It is rather proposed that in Kennedy's region of antidune formation there exist hydraulic conditions where the flow resistance is maximized. It is suggested that such maximum flow resistance is associated with an optimal distance between the bedforms and their height, independently of whether these are antidunes in sand‐ and gravel‐bed rivers or step–pool units in boulder‐bed streams. The considerations of the Kennedy region of antidune formation and the analysis of planform step types depending on stream power both suggest that steep channels have a potential for self‐stabilization by modifying the step–pool structure towards a geometry that provides maximum flow resistance and maximum bed stability. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

Including root reinforcement variability in a probabilistic 3D stability model          下载免费PDF全文

Alessio Cislaghi  Enrico Antonio Chiaradia  Gian Battista Bischetti 《地球表面变化过程与地形》2017,42(12):1789-1806

Forests play a significant role in protecting people, settlements in mountainous terrains from hydrogeomorphic hazards, including shallow landslides. Although several studies have investigated the interactions between forests and slope instabilities, a full understanding of them has not yet been obtained. Additionally, models that incorporate forest stand properties into slope failure probability analyses have not been developed. In principle, physical‐based models, which are powerful tools for landslide hazard analyses, represent an appropriate approach to linking stand properties and slope stability. However, the reliability of these models depends on numerous parameters that describe highly complex geotechnical and hydrological processes (e.g. potential failure depth, saturation ratio, root reinforcement, etc.) that are difficult to measure and model. In particular, the spatial heterogeneity of root reinforcement remains a problem, and the use of physically based models from a forest management perspective has been limited. This paper presents a procedure for assessing slope stability in terms of the Factor of Safety that accounts for forest stand characteristics such as tree density, average diameter at breast height and minimum distance between trees. The procedure combines a three‐dimensional (3D) slope stability model with an evaluation of the variability of root reinforcement in terms of a probability distribution, according to forest characteristics. Monte Carlo simulation is used to account for the residual uncertainties in both stand characteristics and 3D stability model parameters. The proposed method was applied in a subalpine catchment in the Italian Alps, mainly covered by coniferous forest and characterized by steep slopes and high landslide risk. The results suggest that the procedure is highly reliable, according to landslide inventory maps [area under the ROC curve (AUC) is 0.82 and modified success rate (MSR) is 0.70]. Thus, it represents a promising tool for studying the role of root reinforcement in landslide hazard mapping and guiding forest management from a slope stability perspective. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

Simulating earthquake evacuation using human behavior models          下载免费PDF全文

Gian Paolo Cimellaro  Fabrizio Ozzello  Alessio Vallero  Stephen Mahin  Benshun Shao 《地震工程与结构动力学》2017,46(6):985-1002

In classical earthquake risk assessment, the human behavior is actually not taken into account in risk assessment. Agent‐based modeling is a simulation technique that has been applied recently in several fields, such as emergency evacuation. The paper is proposing a methodology that includes in agent‐based models the human behavior, considering the anxiety effects generated by the crowd and their influence on the evacuation delays. The proposed model is able to take into account the interdependency between the earthquake evacuation process, and the corresponding damage of structural and non‐structural components that is expressed in term of fragility curves. The software REPAST HPC has been used to implement the model, and as a case study, the earthquake evacuation by a mall located in Oakland has been used. The human behavior model has been calibrated through a survey using a miscellaneous sample from different countries. The model can be used to test future scenarios and help local authorities in situations where the human behavior plays a key role. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

Conceptual seismic design in performance-based earthquake engineering     

Gerard J. O'Reilly  Gian Michele Calvi 《地震工程与结构动力学》2019,48(4):389-411

A principal aspect of seismic design is the verification of performance limit states, which help ensure satisfactory behaviour within a performance-based earthquake engineering framework. However, it is increasingly acknowledged that while ensuring life safety is a suitable basic design requirement, more meaningful metrics of seismic performance exist. Expected annual loss (EAL) has gained attention in recent years but tends to be limited to seismic assessment. This article proposes a novel conceptual design framework that employs EAL as a design tool and requires very little building information at the design outset. This means that designers may commence from a definition of required EAL and arrive at a number of feasible structural solutions without the need for any detailed design calculations or numerical analysis. This works by transforming the building performance definition to a design solution space using a number of simplifying assumptions. A suitable structural response backbone is subsequently determined and used to identify feasible building typologies and associated structural geometries. The assumptions made to implement such a conceptual design framework are discussed and justified herein followed by a case study application. This proposed design framework is intended to form the first step in seismic design to identify suitable typologies and layouts before subsequent member detailing and design verification. This way, engineers, architects, and clients can make more informed decisions that target certain performance goals at the beginning of design before further refinement.  相似文献   

A facies of Kophobelemnon (Cnidaria,Octocorallia) from Santa Maria di Leuca coral province (Mediterranean Sea)     

Francesco Mastrototaro  Porzia Maiorano  Agostina Vertino  Daniela Battista  Antonella Indennidate  Alessandra Savini  Angelo Tursi  Gianfranco D'Onghia 《Marine Ecology》2013,34(3):313-320

During a research cruise carried out in April 2010, aimed at updating the knowledge on the biodiversity of the Santa Maria di Leuca (SML) cold‐water coral province (Mediterranean Sea), a facies of the sea pen Kophobelemnon stelliferum (Muller, 1776) was found on mud‐dominated bottoms. This finding represents a new species and a new habitat record from the SML coral province as well as a new bathyal facies in the whole Central Mediterranean Sea. The colonies were collected using an epi‐benthic sledge, at depths between 400 and 470 m. A significant positive relationship between polyp number and colony length was detected. Density of the colonies ranged from 0.003 to 0.038 N·m^?2. Differences and affinities between Mediterranean and Atlantic occurrences of K. stelliferum are discussed.  相似文献