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991.
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993.
Rainfall thresholds for the possible landslide occurrence in Sicily (Southern Italy) based on the automatic reconstruction of rainfall events 总被引:1,自引:1,他引:0
Massimo Melillo Maria Teresa Brunetti Silvia Peruccacci Stefano Luigi Gariano Fausto Guzzetti 《Landslides》2016,13(1):165-172
Review of the literature on the reconstruction of the rainfall responsible for slope failures reveals that criteria for the identification of rainfall events are lacking or somewhat subjective. To overcome this problem, we developed an algorithm for the objective and reproducible reconstruction of rainfall events and of rainfall conditions responsible for landslides. The algorithm consists of three distinct modules for (i) the reconstruction of distinct rainfall events, in terms of duration (D, in h) and cumulated event rainfall (E, in mm), (ii) the identification of multiple ED rainfall conditions responsible for the documented landslides, and (iii) the definition of critical rainfall thresholds for possible landslide occurrences. The algorithm uses pre-defined parameters to account for different seasonal and climatic settings. We applied the algorithm in Sicily, southern Italy, using rainfall measurements obtained from a network of 169 rain gauges, and information on 229 rainfall-induced landslides occurred between July 2002 and December 2012. The algorithm identified 29,270 rainfall events and reconstructed 472 ED rainfall conditions as possible triggers of the observed landslides. The algorithm exploited the multiple rainfall conditions to define objective and reproducible empirical rainfall thresholds for the possible initiation of landslide in Sicily. The calculated thresholds may be implemented in an operational early warning system for shallow landslide forecasting. 相似文献
994.
Raphael Cezar Grabowski Maria Lucia Negreiros-Fransozo Antonio Leão Castilho 《中国海洋湖沼学报》2016,34(1):125-135
The predictability of certain environmental factors that affect the life cycle of the seabob shrimp Xiphopenaeus kroyeri (Heller, 1862) was evaluated in a study of its reproductive biology in an area adjacent to Babitonga Bay, State of Santa Catarina, Brazil. Monthly sampling was conducted from July 2010 through June 2011 at depths of 5, 8, 11, 14, and 17 m. 76 004 individuals were obtained, with a pronounced peak in absolute abundance in austral autumn (34 208), coinciding with the annual closed season from March to May. Grain size composition of the sediment showed the closest relationship to the distribution of individuals (multiple linear regression, P <0.05), related to their burying habit. The observed correlations between the abundance of reproductive males (bearing spermatophores) and females with spent gonads (cross-correlation, P <0.05), and between reproductive males and reproductive females (with a 1-month lag) suggest that the peak of reproductive males preceded the peak of female ones. This result agrees with the pattern expected for females, which copulate in post-ecdysis (spent gonads). Spawning seemed to take place at greater depths, as evidenced by the concentration of reproductive females in these areas. The reproductive activities observed here confirm that this species follows a tropical/subtropical reproductive pattern, spawning continuously throughout the year, with the highest peaks in spring and autumn. The data indicate that the juvenile recruitment period observed in August-September resulted from the reproductive output noted in April–May. Additionally, the reproductive period recorded in November led to the juvenile peak observed in March–May. 相似文献
995.
Maria I. Todorovska 《地震工程与结构动力学》1998,27(10):1031-1051
A mathematical model for a three-component accelerograph is presented that accounts for the effects of transducer misalignment and cross-axis sensitivity. The former refers to departures in the alignment of the transducer penduli (typically of the order of few degrees) from an ideal orthogonal system, and the latter to a transducer recording components of motion in directions other than its principal sensitivity axis. Transducer misalignment magnifies the effects of cross-axis sensitivity. These effects are significant only for large amplitude recordings (peak acceleration close to 1g), for example in the near-field of the 1994 Northridge, California, earthquake. The misalignment angles and the angular amplification constant can be determined by a static tilt test, performed in the field, and solving a generalized inverse problem. This paper presents an algorithm for solution of this inverse problem on a routine basis. Practical implementation of the algorithm and results for 76 instruments of the Los Angeles Strong Motion Array are presented in a separate paper. © 1998 John Wiley & Sons, Ltd. 相似文献
996.
Maria I. Todorovska Elena I. Novikova Mihailo D. Trifunac Sanja S. Ivanovi 《地震工程与结构动力学》1998,27(10):1053-1068
Results are presented of recent sensitivity calibration of 76 accelerographs (SMA-1) of the Los Angeles Strong Motion Array. These have pendulum-like transducers and optical recording system. One characteristic of their design is off-axis sensitivity, which is magnified by transducer misalignment. A new calibration procedure was applied, which considers off-axis sensitivity and measures the angles of misalignment (φ and ψ), as well as the incident angle of the light beam onto the film (θ0). These are required (1) for accurate estimation of sensitivity, and (2) for proper instrument correction of recorded accelerograms which considers also cross-axis sensitivity and misalignment. These effects are important near large acceleration peaks (approaching and exceeding 1g), e.g. like the ones recorded near the source of the 1994 Northridge earthquake (ML=6·4). This earthquake was recorded by 65 stations of the Los Angeles Strong Motion Array, at epicentral distances from 2 to 85 km. Histograms showing distribution of the misalignment angles, light beam incidence angle θ0 (for unloaded position) and the transducer sensitivities are presented. These indicate that the misalignment angles are typically 1–1·5°, but may also be 3–4°. Angle θ0 (usually neglected), is mostly between ±8°, but may reach ±12°. Assuming θ0=0 leads to systematically smaller values of the measured sensitivity (e.g. by ∼3% for θ0=8° and ∼4% for θ0=12°). Comparison of the newly measured sensitivities with those measured prior to installation (in 1979/1980), sold, shows that, in general, the new values are systematically smaller. The difference is typically within 5 per cent, but in some cases is as large as 10 per cent. Other principal sources of the observed differences and their mechanisms are discussed. Those include long-term changes in the transducers (e.g. change of stiffness, reflected in changes of the natural frequency) and differences in the calibration procedure (e.g. errors associated with manual reading film records with tilt test data, and with transducer and instrument housing misalignment). The presented results may be considered typical of similar strong motion arrays worldwide. © 1998 John Wiley & Sons, Ltd. 相似文献
997.
de Azevedo Reis Gabriela de Souza Filho Francisco Assis Nelson Donald Robert Rocha Renan Vieira da Silva Samiria Maria Oliveira 《Natural Hazards》2020,104(2):1781-1799
Natural Hazards - Although climate change vulnerability research in general has increased over the last decade, Latin American countries have more directed more limited efforts toward vulnerability... 相似文献
998.
Jaccard Camille-Jean Abbruzzese Jacopo Maria Howald Erika Prina 《Natural Hazards》2020,100(1):459-459
Natural Hazards - Rock falls threaten human lives and assets in mountainous regions all over the world. Protection measures are one of the most effective solutions for mitigating rock fall-related... 相似文献
999.
Ali Syeda Maria Khalid Bushra Akhter Asma Islam Aneeza Adnan Shahzada 《Natural Hazards》2020,103(2):2533-2559
Natural Hazards - Frequency and intensity of extreme weather events are immensely changing throughout the world. This study aims to give insight into the changing climatic patterns leading to... 相似文献
1000.
Concentration of damage of buildings near the edge of cliff-type topographies has been observed during a number of recent
earthquakes and interpreted by numerical dynamic analyses that illustrate the amplification of the horizontal acceleration
and the generation of parasitic vertical acceleration near the tip of slopes. The paper performs a detailed parametric numerical
analysis to investigate the ability of mitigating this topographic effect using anchors and piles. A typical field case, the
Aegion slope of Greece, is considered. Different input motions are applied. The results illustrated that anchors and piles
can be effective in mitigating the topographic effect. The main issue is that if the part of the slope in which topographic
amplification occurs is connected to that at larger depths, in which the acceleration is smaller, then the accelerations at
the top of the slope have to become more uniform and smaller. For typical diameter and material properties of anchors/piles
the effectiveness of the mitigation depends on the length, inclination, location and number of anchors/piles. An optimum configuration
of anchors/piles mitigating the topographic effect is proposed. 相似文献