Numerical and functional representations of regional heat flow in South America

A summary of heat flow data acquired over recent years in several areas in the eastern (Brazil and Paraguay) and western (Bolivia, Chile, Colombia and Ecuador) parts of South American continent are presented. The improvements in the database have allowed numerical representations of heat flow for southeastern and central segments of the Precambrian fold belts in Brazil, Central Andean cordilleras in Chile and Bolivia, Southern Volcanic arc in Peru, Neuquén Province in southwestern Argentina, Chaco basin in Paraguay, Oriente basin in Ecuador and the system of pericratonic basins in north central Colombia. The maps reveal considerable variability in heat flow, not only between the main tectonic units but also within them. The intra-regional variations seem to originate mainly from complexities in local geologic structures while the inter-regional ones seem to point to action of deep-seated tectonic processes. The cordilleran regions are, in general, characterized by relatively high heat flow (>70 mW/m²), compared with the coastal regions to the west and the Pre-cordilleran basins to the east. In the eastern part of the continent, heat flow is low to normal (<60 mW/m²), the exceptions being the Mesozoic rift basins, areas of Cenozoic alkaline intrusions and some isolated belts of overthrust tectonics in the central parts of Brazil. There are indications that heat flow is high in the Patagonian Platform relative to that found in the Brazilian Platform.In addition, polynomial methods were employed for examining large-scale variations of heat flow over the continent. Specifically, a general-purpose least square solution was used to determine the coefficients of up to fourth order in latitude and longitude. Some of the large-scale trends seen in low order polynomial representations seem to be indicative of the nature of deep-seated heat transfer processes. The systematic increase in regional heat flow in the north-south direction is an example. It is considered as the consequence of thermal blanketing effect of the continental segment of the South American lithosphere. Trends seen in higher order polynomials seem to be associated with regional tectonic patterns and subduction-related magmatism. Prominent among these are east-west trending belts of low heat flow in northern Peru and in central Chile, as well as the high heat flow belts in northern Chile, Altiplano of Bolivia and northwestern Argentina. Limitations arising from low data density and uneven geographic distribution warrant higher degree polynomial representations.     

网络环境下分区统计地图制图子系统的设计与实现

分析了网络环境下分区统计地图表达信息的特点,根据其可视化地理统计信息的需要,运用Java Ap-plet技术,设计和开发了网络环境下交互式分区统计地图制图子系统。     

Seismic hazard assessment in Jordan and its vicinity

The earthquake hazard in Jordan and its vicinity is assessed on the basis of probabilistic methods. For this purpose, an updated earthquake catalog is compiled which covers the period between AD 1–1989. The earthquakes lie between latitudes 27.0°-35.5° N and longitudes 32.0°-39.0° E. Thirteen seismic zones are defined on a regional seismic and tectonic map presented for the area. Point-source and line-source models are used. The seismic hazard parameters, namely, theb-parameter (of the Gutenberg-Richter relation),m ₁ (the upper bound magnitude), and ₄ (the annual rate of occurrence of earthquakes with local magnitudeM _L 4.0) are calculated for each zone. The results of the seismic hazard assessment are displayed as iso-acceleration contours expected to be exceeded during typical economic life times of structures, i.e. 50 and 100 years. For each model, two seismic hazard maps are derived. In order to determine the importance of the South-eastern Mediterranean zone and the north part of the Red Sea zone from a seismic hazard point of view for Jordan, one seismic hazard map which corresponds to 50 years' economic life for every model, excluding the seismicity of these zones, is derived.     

A MODEL FOR QUANTITATIVELY ESTIMATING SHORT-RANGE PRECIPITATION BASED ON GMS DIGITALIZED CLOUD MAPS—PART Ⅱ:ASSESSMENT OF RESULTS FROM THE MODEL FOR SATELLITE-IMAGE QUANTITATIVELY ESTIMATING PRECIPITATION

This is Part Ⅱ of this series.It introduces the technique for recognizing MαCS phased properties and its precipitation center or centers by means of dynamic digitalized cloud maps and presents the assessment of the effectiveness of the model proposed in Part Ⅰ as to its fitting and forecasting accuracy.     

1∶20万桐柏-信阳区域地球化学调查基本图件编制

桐柏—信阳一带区域地球化学调查是全国区域化探扫面的一部分。编图中涉及19和20投影带及4个1∶20万图幅的拼接,制图中存在不少技术难题。为了避免2个投影带产生的裂隙坐标不统一,将20带数据转换到19带,然后在高斯—克吕格座标表中查取座标自然值,并计算座标通用值后进行座标展绘,取得了较好的制图效果。     

Mixing Methodologies in Seismic Hazard Assessment via a Logic Tree Procedure: An Application for Eastern Spain

This study provides a procedure for assessing seismic hazardand uncertainties in regions that are characterised by a large non-instrumental earthquakedatabase and a seismic and tectonic behaviour which doesn't allow an evident seismic zonation.This procedure is a synthesis of the non-zoning or non-parametric methodology (using extremevalues distribution functions as proposed by Epstein and Lomnitz, 1966) and the zoning orparametric methodology (using the theorem of total probability as proposed by Cornell, 1968)via a logic tree procedure taking into consideration the advantages offered by each of these.Taking the area which we shall describe as the east coast of Spain and surrounding inland areas,an application was made and a specific logic tree was developed in order to solve the problems anduncertainties related to the evaluation of the seismic hazard using both methodologies. The use of thelogic tree allowed the systematisation of a large number of solutions obtained. A number of relevantresults were obtained which show that in some cases there are great differences in the seismichazard results provided by the non-zoning and the zoning methodologies. In these cases, mean value andstandard deviation of the obtained results provide an intermediate solution to the over-conservativeestimation provided by the non-zoning methodology and the lowest results provided by the zoningmethodology. In other cases results provided by both methodologies are significantly closer.In any case, synthesis among both methodologies gives a wider knowledge of the uncertaintiesassociated with the seismic hazard results. Finally uncertainties increase with the decreaseof the annual probability of exceedence and in sites with a seismic history of large size earthquakes.     

Seismic Ground Motion Zoning Maps of the Pangxi Region

The seismotectonic environment and seismic activity in Southwest China region were studied based on new data and new results obtained during the Eighth and Ninth Five-Year Plans,the seismic areas and zones and potential seismic source zones were determined.and the relation between seismic activity parameters and ground motion attenuation was determined.Finally the seismic gound motion zoning maps of the Pangxi region was compiled by using the multi-parameter and multi-scheme method.     

基于地理信息数据库编制专题图过程中常见问题初探

基于地理信息数据库编制专题图已逐渐成为编制各种专题图、地形图的主要方式,本文针对编制过程中的常见问题,分析了问题产生的原因,并提出了相应的解决办法,在总结经验的基础上,为读者进行相关工作提供了建议。     

MAPGIS在数字化地质制图中的应用技巧

结合工作实践,将MAPGIS在数字化地质制图中常遇到的普遍问题,如MAPGIS文件改名后打不开、图件打印不出及因项目文件排序错乱而引起的图幅显示不整齐等问题,用简捷有效的方法和技巧解决,提高了制图速度,使图面规范化,幅面更加美观。     

The chemical composition of the surface system of Peneos river, Thessaly/Central Greece

 Peneos is the mainstream for the drainage of Thessaly's basin. It contributes significantly in recharging the aquifers, as well as to the direct irrigation water, since there is intense agricultural activity in the basin of Thessaly. The investigation of the hydrochemical conditions of the surface water system of Peneos showed that the chemical composition is related to the lithology of the aquifers of the basin, the anthropogenic influence and the biological activity. The chemical composition of this system changes in time and space. The salinity decreases during the winter period, in contrast to the summer period when it increases drastically. The lower values of TDS appear in the upstream part of the river (95–124 mg/l) whereas downstream, the values of TDS increase significantly (400–632 mg/l). The hydrochemical type Ca-Mg-HCO₃ dominates the largest part of the river while it changes to NA-Cl in the estuary. The concentrations of the dissolved species in the main Peneos river are higher than in the spring waters. Peneos is the most polluted river in Greece. The concentration of the pollutants is higher at the downstream part of the river, but is lower than the accepted upper limits. The use of the surface water of the system of Peneos river for irrigation purposes based on the SAR factor is acceptable because the absorption ratio for Na and salinity are low and medium respectively. Received: 27 October 1997 · Accepted: 21 September 1998