Assessment of seismic hazard for the Sannio-Matese area of Southern Italy — A summary     

M. S. Barbano  J. J. Egozcue  M. García Fernández  A. Kijko  J. Lapajne  D. Mayer-Rosa  V. Schenk  Z. Schenková  D. Slejko  G. Zonno 《Natural Hazards》1989,2(3-4):217-228

The working group on Test Regions for Evaluation of Methods for Seismic Hazard Assessment in Europe (TERESA), consisted of 15 members from 10 different European countries. Methods and experience gathered in these countries have been compared and discussed for two test areas in Europe: the Sannio-Matese region, Southern Italy, with high seismic activity, and the border region between Belgium, The Netherlands, and Federal Republic of Germany, with low activity.This paper summarizes the results for one of the test areas, Sannio-Matese. Most of the participants used statistical procedures to assess earthquake hazard, receiving results in terms of probability of occurrence for intensity as the ground-motion parameter. It was found that careful preparation of input data and parameters is the major influencing factor, therefore most of the efforts of the working group was devoted to this task.The scatter of the obtained results of the group is considerable, mainly because of the uncertainties in the data and the subjectiveness involved in the procedures. For better control of both factors, more objective methods have to be developed.  相似文献   

Seismic hazard computations for regions with low earthquake activity — A case study for the Belgium,The Netherlands and NW Germany area     

Theo de Crook  Vladimír Schenk  M. S. Barbano  F. Colombo  J. J. Egozcue  M. García-Fernández  P. Kottnauer  G. Leydecker  F. Mantlík  Z. Schenková  G. Zonno 《Natural Hazards》1989,2(3-4):229-236

The algorithms to evaluate seismic hazard, used and/or developed by five teams participating in the TERESA project, applied to the low seismicity area Belgium, The Netherlands and NW Germany are compared. The main differences in the results can be explained by the majority criterion of Egozcue et al. (1989), the differences in the upper bound and zonification and, in some cases, by a higher attenuation.  相似文献   

Seismic activity related to the 1991 eruption of Colima Volcano,Mexico     

Francisco Núñez-Cornú  F. Alejandro Nava  Servando De la Cruz-Reyna  Zenón Jiménez  Carmen Valencia  Rosalía García-Arthur 《Bulletin of Volcanology》1994,56(3):228-237

Ten years after the last effusive eruption and at least 15 years of seismic quiescence, volcanic seismic activity started at Colima volcano on 14 February 1991, with a seismic crisis which reached counts of more than 100 per day and showed a diversity of earthquake types. Four other distinct seismic crises followed, before a mild effusive eruption in April 1991. The second crisis preceded the extrusion of an andesitic scoriaceous lava lobe, first reported on 1 March; during this crisis an interesting temporary concentration of seismic foci below the crater was observed shortly before the extrusion was detected. The third crisis was constituted by shallow seismicity, featuring possible mild degassing explosion-induced activity in the form of hiccups (episodes of simple wavelets that repeat with diminishing amplitude), and accompanied by increased fumarolic activity. The growth of the new lava dome was accompanied by changing seismicity. On 16 April during the fifth crisis which consisted of some relatively large, shallow, volcanic earthquakes and numerous avalanches of older dome material, part of the newly extruded dome, which had grown towards the edge of the old dome, collapsed, producing the largest avalanches and ash flows. Afterwards, block lava began to flow slowly along the SW flank of the volcano, generating frequent small incandescent avalanches. The seismicity associated with the stages of this eruptive activity shows some interesting features: most earthquake foci were located north of the summit, some of them relatively deep (7–11 km below the summit level), underneath the saddle between the Colima and the older Nevado volcanoes. An apparently seismic quiet region appears between 4 and 7 km below the summit level. In June, harmonic tremors were detected for the first time, but no changes in the eruptive activity could be correlated with them. After June, the seismicity decreasing trend was established, and the effusive activity stopped on September 1991.  相似文献   

The 2001 Mesoscale Convective Systems over Iberia and the Balearic Islands     

R. García-Herrera  D. Barriopedro  E. Hernández  D. Paredes  J. F. Correoso  L. Prieto 《Meteorology and Atmospheric Physics》2005,90(3-4):225-243

Summary This paper characterizes Mesoscale Convective Systems (MCSs) during 2001 over Iberia and the Balearic Islands and their meteorological settings. Enhanced infrared Meteosat imagery has been used to detect their occurrence over the Western Mediterranean region between June and December 2001 according to satellite-defined criteria based on the MCS physical characteristics. Twelve MCSs have been identified. The results show that the occurrence of 2001 MCSs is limited to the August–October period, with September being the most active period. They tend to develop during the late afternoon or early night, with preferred eastern Iberian coast locations and eastward migrations. A cloud shield area of 50.000 km² is rarely exceeded. When our results are compared with previous studies, it is possible to assert that though 2001 MCS activity was moderate, the convective season was substantially less prolonged than usual, with shorter MCS life cycles and higher average speeds. The average MCS precipitation rate was 3.3 mm·h⁻¹ but a wide range of values varying from scarce precipitation to intense events of 130 mm·24 h⁻¹ (6 September) were collected. The results suggest that, during 2001, MCS rainfall was the principal source of precipitation in the Mediterranean region during the convective season, but its impact varied according to the location. Synoptic analysis based on NCEP/NCAR reanalysis show that several common precursors could be identified over the Western Mediterranean Sea when the 2001 MCSs occurred: a low-level tongue of moist air and precipitable water (PW) exceeding 25 mm through the southern portion of the Western Mediterranean area, low-level zonal warm advection over 2 °C·24 h⁻¹ towards eastern Iberia, a modest 1000–850 hPa equivalent potential temperature (θ_e) difference over 20 °C located close to the eastern Iberian coast, a mid level trough (sometimes a cut-off low) over Northern Africa or Southern Spain and high levels geostrophic vorticity advection exceeding 12·10⁻¹⁰ s⁻² over eastern Iberia and Northern Africa. Finally, the results suggest that synoptic, orographic and a warm-air advection were the most relevant forcing mechanisms during 2001.  相似文献   

Factors affecting arsenic concentration in groundwaters from Northwestern Chaco-Pampean Plain,Argentina     

María Gabriela García  Ondra Sracek  Diego Sebastián Fernández  Margarita del Valle Hidalgo 《Environmental Geology》2007,52(7):1261-1275

The concentration of arsenic measured in groundwater from three aquifers in the study area located in the Eastern Tucuman province, Argentina, mostly depends on the lithology, but the spatial and temporal variations of concentrations seem to be also controlled by pH changes, climatic factors, and human perturbations. The highest concentrations of As (more than 1,000 μg L⁻¹) were found in the shallow aquifer, made of As-rich loess, while the lowest concentrations were measured in the deep confined aquifer, consisting of alternating layers of alluvial sands/gravels and clays. Intermediate values were measured in the semiconfined aquifer made of the fluvial sediments deposited in the Salí River valley, that alternate in the upper part of the sedimentary sequence with layers of loess. Because most of As in the loess is considered to be adsorbed onto Fe-oxyhydroxide coatings, the increase of pH in the flow direction (west-east) leads to increasing arsenic concentrations towards the eastern border of the study area. The decomposition of organic wastes poured into the Salí River or associated with local and diffuse sources of contamination in the eastern part of the study area depletes dissolved oxygen, which leads to the reductive dissolution of Fe and Mn oxyhydroxides, and to the subsequent release of the adsorbed and co-precipitated As. This process mainly affects shallow groundwater and the upper part of the semiconfined aquifer. Geochemical and hydrological data also suggest that rising water table levels at the end of the wet season may also lead to reductive dissolution of As-rich Fe oxyhydroxides in the shallow aquifer.  相似文献   

Paleolimnological assessment of human impacts on an urban South African lake     

F. García-Rodríguez  C. R. Anderson  J. B. Adams 《Journal of Paleolimnology》2007,38(3):297-308

North End Lake is a polluted and eutrophic freshwater system located in Port Elizabeth, South Africa. Since the lake is expected to be used for recreational/tourist purposes by 2010, a rehabilitation program will have to be designed. For this reason, we retrieved a sediment core from the central region of the lake to decipher the effect of historical human impacts on the water body. Pre-disturbance paleolimnological inferences indicate that the lake was likely mesotrophic. After ∼1831, when sheep farming activities were undertaken in the catchment, increases in trophic state and changes in sediment composition were observed. After ∼1937, increases in trace metal levels, organic matter, spheroidal carbonaceous particles (SCP) and changes in sediment composition were recorded. The system became eutrophic as indicated by the dominance of the diatom Actinocyclus normanii, a cosmopolitan species often observed in systems where water quality has been dramatically degraded. The conditions worsened after 1986 because of the construction of a storm-water retention system, which intentionally channeled storm-water runoff into the lake. Because of this, extremely high values of fecal coliforms (i.e. 2 × 10⁶ every 100 ml) have been measured in the water column. The paleolimnological information identified the sharp increase in organic content in the uppermost section of the core, and this could be correlated to the operation of the storm-water retention system. Therefore, as an immediate management measure, we suggest that the storm-water retention system should either no longer be utilized, or the storm-water runoff should be treated before disposal into the lake. In addition, an effective sewage system has to be constructed.  相似文献   

Analysis of the weightiness of site effects on reinforced concrete (RC) building seismic behaviour: The Adra town example (SE Spain)   总被引：1，自引：0，他引：1  

Manuel Navarro  Francisco Vidal  Takahisa Enomoto  Francisco J. Alcalá  Antonio García‐Jerez  Francisco J. Sánchez  Norio Abeki 《地震工程与结构动力学》2007,36(10):1363-1383

The damage distribution in Adra town (south‐eastern Spain) during the 1993 and 1994 Adra earthquakes (5.0 magnitude), that reached a maximum intensity degree of VII (European Macroseismic Scale (EMS scale)), was concentrated mainly in the south‐east zone of the town and the most relevant damage occurred in reinforced concrete (RC) buildings with four or five storeys. In order to evaluate the influence of ground condition on RC building behaviour, geological, geomorphological and geophysical surveys were carried out, and a detailed map of ground surface structure was obtained. Short‐period microtremor observations were performed in 160 sites on a 100m × 100m dimension grid and Nakamura's method was applied in order to determine a distribution map of soil predominant periods. Shorter predominant periods (0.1–0.3 s) were found in mountainous and neighbouring zones and larger periods (greater than 0.5 s) in thicker Holocene alluvial fans. A relationship T = (0.049 ± 0.001)N, where T is the natural period of swaying motion and N is the number of storeys, has been empirically obtained by using microtremor measurements at the top of 38 RC buildings (ranging from 2 to 9 storeys). 1‐D simulation of strong motion on different soil conditions and for several typical RC buildings were computed, using the acceleration record in Adra town of the 1993 earthquake. It is noteworthy that all the aforementioned results show the influence of site effects in the degree and distribution of observed building damage. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Evolutionary properties of stochastic models of earthquake accelerograms: Their dependence on magnitude and distance     

J. Alamilla  L. Esteva  J. García-Pérez  O. Díaz-López 《Journal of Seismology》2001,5(1):1-21

An approach to generate artificial earthquakeaccelerograms on hard soil sites is presented. Eachtime-history of accelerations is considered as arealization of a non-stationary gaussian stochasticprocess, with statistical parameters depending onmagnitude and source-to-site distance. In order tolink the values of these parameters for each groundmotion record with the corresponding magnitude andsource-to-site distance, semi-empirical functionalrelations called generalized attenuationfunctions are determined. The set of realground-motion time histories used to obtain thesefunctions correspond to shocks generated at differentsources and recorded at different sites in thevicinity of the southern coast of Mexico. The resultsshow significant dispersion in the parameters of themodel adopted, which reflect that associated with thereal earthquakes included in the sample employed.The problem of conditional simulation of artificialacceleration time histories for prescribed intensitiesis briefly presented, but its detailed study is leftfor a companion paper. The criteria and modelsproposed are applied to generate two families ofartificial acceleration records for recurrenceintervals of 100 and 200 years at a specific sitelocated in the region under study. The results shownin this article correspond to acceleration timehistories recorded on firm ground for earthquakesgenerated at the subduction zone that runs along thesouthern coast of Mexico, and cannot be generalized tocases of earthquakes generated at other sources orrecorded at other types of local conditions. Thismeans that the methods and functional forms presentedhere are applicable to these other cases, but thevalues of the parameters that characterize thosefunctions may differ from those presented here.  相似文献   

ON THE NUMBER OF FRACTIONS TO COMPUTE TRANSPORT OF SEDIMENT MIXTURES     

Pedro A. BASILE Center for Hydroenvironmental Research  National University of Rosario   《国际泥沙研究》2001,16(3)

1 INTRODUCTIONMany hydro-momhological mathematical models neglect the innuence of river bed maerialheterogeneity and its time and space changes during transport and related erosion/dePosition processes. Inthese models a rePresentative diameter of the river bed grain-size distribution (for examPle d5o) isspecified as initial data in each comPutational point of the modeled domain. Different d5o can be assignedto each ghd point but temPoral changes in bed material gradation cannot be simula…  相似文献   

Chemical behavior of the Salí River, Province of Tucumán, Argentina     

M. Galindo  M. Vece  M. Perondi  M. Monserrat Aráoz  G. García  M. del V. Hidalgo  M. Apella  M. Blesa 《Environmental Geology》2001,40(7):847-852

Major ionic composition and other chemical parameters were determined at five sampling stations on the Salí River (Province of Tucumán, Argentina). The heavy human usage of the river causes increased levels of dissolved ions, from the dissolution of halite and gypsum, and from the weathering of basic sediments. Correlations demonstrate that sodium chloride and sulphate, and calcium carbonate are the main contributors to dissolved ions in the river. In the polluted region, south of the Celestino Gelsi dam, the main source of calcium and sulphate is the dissolution of gypsum. Large amounts of halite are also dissolved. Weathering of biotite, K-feldspar and albite are suggested by the data. Conductivity, dissolved oxygen and organic matter all indicate severe contamination by organic matter (mainly from sugar-cane processing) in the lower course. The data also demonstrate a substantial improvement in water quality before the discharge of the river at the Río Hondo dam. Data from the Colorado (a tributary of the Salí River) and Medina rivers are also analyzed and compared.  相似文献