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41.
Alexander I. Gorshkov Giuliano F. Panza Alexander A. Soloviev Abdelkrim Aoudia Antonella Peresan 《地学学报》2009,21(4):257-264
We introduce a new method based on the analysis of the topographical alignments and used to delineate the structural boundaries of the nodes, which permits the definition of relatively narrow earthquake-prone areas by the pattern recognition approach. The structurally bounded nodes capable of earthquakes with M ≥ 6.0, identified with pattern recognition, in fact, cover a significantly smaller area of the study region as compared with that defined by Gorshkov et al. (2004) who used conventional circles. The proposed method thus improves the precision in the location of potential large earthquakes. 相似文献
42.
43.
Franco Vaccari M. Yanger Walling William K. Mohanty Sankar K. Nath Akhilesh K. Verma A. Sengupta Giuliano F. Panza 《Pure and Applied Geophysics》2011,168(3-4):479-493
Kolkata, one of the oldest cities of India, is situated over the thick alluvium of the Bengal Basin, where it lies at the boundary of the zone III and zone IV of the seismic zonation map of India. An example of the study of site effects of the metropolitan Kolkata is presented based on theoretical modeling. Full synthetic strong motion waveforms have been computed using a hybrid method that combines the modal summation and finite difference techniques. The 1964 Calcutta earthquake, which was located at the southern part of Kolkata, is taken as the source region, with the focal mechanism parameters of dip?=?32°, strike?=?232° and rake?=?56°. Four profiles are considered for the computation of the synthetic seismograms from which the maximum ground acceleration (A MAX) is obtained. Response spectra ratios (RSR) are then computed using a bedrock reference model to estimate local amplifications effects. The A MAX varies from 0.05 to 0.17?g and the comparison of the A MAX with the different intensity scales (MM, MSK, RF and MCS) shows that the expected intensity is in the range from VII to X (MCS) for an earthquake of magnitude 6.5 at an epicentral distance of about 100?km. This theoretical result matches with the empirical (historical and recent) intensity observations in Kolkata. The RSR, as a function of frequency, reaches the largest values (largest amplification) in the frequency range from 1.0 to 2.0?Hz. The largest site amplification is observed at the top of loose soil. 相似文献
44.
Giuliano Di Baldassarre Guy Schumann Luigia Brandimarte Paul Bates 《Surveys in Geophysics》2011,32(3):255-269
It is widely recognised that remote sensing can support flood monitoring, modelling and management. In particular, satellites carrying Synthetic Aperture Radar (SAR) sensors are valuable as radar wavelengths can penetrate cloud cover and are insensitive to daylight. However, given the strong inverse relationship between spatial resolution and revisit time, monitoring floods from space in near real time is currently only possible through low resolution (about 100 m pixel size) SAR imagery. For instance, ENVISAT-ASAR (Advanced Synthetic Aperture Radar) in WSM (wide swath mode) revisit times are of the order of 3 days and the data can be obtained within 24 h at no (or low) cost. Hence, this type of space-borne data can be used for monitoring major floods on medium-to-large rivers. This paper aims to discuss the potential for, and uncertainties of, coarse resolution SAR imagery to monitor floods and support hydraulic modelling. The paper first describes the potential of globally and freely available space-borne data to support flood inundation modelling in near real time. Then, the uncertainty of SAR-derived flood extent maps is discussed and the need to move from deterministic binary maps (wet/dry) of flood extent to uncertain flood inundation maps is highlighted. 相似文献
45.
Kenechukwu Okoli Korbinian Breinl Luigia Brandimarte Anna Botto Elena Volpi Giuliano Di Baldassarre 《水文科学杂志》2013,58(13-14):1913-1926
ABSTRACTThis study compares model averaging and model selection methods to estimate design floods, while accounting for the observation error that is typically associated with annual maximum flow data. Model selection refers to methods where a single distribution function is chosen based on prior knowledge or by means of selection criteria. Model averaging refers to methods where the results of multiple distribution functions are combined. Numerical experiments were carried out by generating synthetic data using the Wakeby distribution function as the parent distribution. For this study, comparisons were made in terms of relative error and root mean square error (RMSE) referring to the 1-in-100 year flood. The experiments show that model averaging and model selection methods lead to similar results, especially when short samples are drawn from a highly asymmetric parent. Also, taking an arithmetic average of all design flood estimates gives estimated variances similar to those obtained with more complex weighted model averaging. 相似文献
46.
Lihua Fang Jianping Wu Zhifeng Ding Weilai Wang Giuliano Francesco Panza 《地震科学(英文版)》2010,23(5):477-486
We collected continuous noise waveform data from January 2007 to February 2008 recorded by 190 broadband and 10 very broadband stations of the North China Seismic Array.The study region is divided into grid with interval 0.25°×0.25°,and group velocity distribution maps between 4 s and 30 s are obtained using ambient noise tomography method.The lateral resolution is estimated to be 20-50 km for most of the study area.We construct a 3-D S wave velocity model by inverting the pure path dispersion curve at each grid using a genetic algorithm with smoothing constraint.The crustal structure observed in the model includes sedimentary basins such as North China basin,Yanqing-Huailai basin and Datong basin.A well-defined low velocity zone is observed in the Beijing-Tianjin-Tangshan region in 22-30 km depth range,which may be related to the upwelling of hot mantle material.The high velocity zone near Datong,Shuozhou and Qingshuihe within the depth range of 1-23 km reveals stable characteristics of Ordos block.The Taihangshan front fault extends to 12 km depth at least. 相似文献
47.
ABSTRACTThis study assessed the utility of EUDEM, a recently released digital elevation model, to support flood inundation modelling. To this end, a comparison with other topographic data sources was performed (i.e. LIDAR, light detection and ranging; SRTM, Shuttle Radar Topographic Mission) on a 98-km reach of the River Po, between Cremona and Borgoforte (Italy). This comparison was implemented using different model structures while explicitly accounting for uncertainty in model parameters and upstream boundary conditions. This approach facilitated a comprehensive assessment of the uncertainty associated with hydraulic modelling of floods. For this test site, our results showed that the flood inundation models built on coarse resolutions data (EUDEM and SRTM) and simple one-dimensional model structure performed well during model evaluation.
Editor Z.W. Kundzewicz; Associate editor S. Weijs 相似文献
48.
ABSTRACT When rainfall does not meet crop water requirements, supplemental irrigation is needed to maintain productivity. On-farm ponds can prevent excessive groundwater exploitation – to the benefit of the whole community – but they reduce the cultivated area and require investments by each farmer. Thus, choosing the source of water for irrigation (groundwater vs on-farm pond) is a problem of collective action. An agent-based model is developed to simulate a smallholder farming system; the farmers’ long-/short-view orientation determines the choice of the water source. We identify the most beneficial water source for economic gain and its stability, and how it can change across communities and under future climate scenarios. By using on-farm ponds, long-view-oriented farmers provide collective advantages but have individual advantages only under extreme climates; a tragedy of the commons is always possible. Changes in farmers’ attitudes (and hence sources of water) based on previous experiences can worsen the economic outcome. 相似文献
49.
Summary The dispersion of higher modes of surface waves over a region covered by an array of stations can be measured by applying a frequency-wavenumber transform to segments of the signals in these stations, centered at a number of group-velocities. Thus, at a fixed period, modes appear as separate maxima in a display of the power spectrum on a phase-velocity vs. group velocity plane.For regions of mild lateral heterogeneity, the main source of error is shown to be due to the inadequacy of the array-response. Numerical experiments with synthetic signals indicate that a precision of the order of 1% can be obtained with a realistic number of stations. Improvements should be obtained by averaging data obtained from different events. The danger of misidentification of modes can be reduced by iteratively removing the sidelobes from the mode-separation diagram. 相似文献
50.
Instability of resonant trapped gravity waves is proposed as the mechanism responsible for the creation of turbulent patches in the inversion capping a well developed convective layer. The plume circulation of the convective layer results in a periodic forcing at the base of the inversion layer; trapped gravity waves in resonance with such forcing are considered. Good agreement with experimental results is obtained.Now at the Istituto di Fisica della Università di Urbino Via S. Chiara 61100 Urbino (Ps.) Italy. 相似文献