Analysis of a large extent aeromagnetic survey near the geomagnetic equator (Minas Gerais,Brazil)     

M. S. M. Mantovani  W. Shukowsky 《Pure and Applied Geophysics》1982,120(4):784-794

A large extent aeromagnetic survey, covering a 9°×9° degree of a Precambrian shield area in SE Brazil, was used to analyse long wavelength magnetic anomalies with the purpose of determining the magnetic structure of the lithosphere.Data analysis based on a novel approach to the estimation of the parameters in the statistical model ofSpector andGrant (1970), reveals a highly magnetized lower crust, bounded by an essentially non-magnetic upper mantle. The highly magnetized layer can be associated with a higher density lower crust model, derived from gravity and seismic data available in the area, suggesting a compositional transition from upper to lower crust.It was also verified that the operation of reduction to the pole, which is singular at the geomagnetic equator, performs quite satisfactorily at the low geomagnetic inclination of the area, bringing into accordance the long wavelength anomalies with the structural trends.  相似文献   

热化学硫酸盐还原作用对碳酸盐岩气藏的化学改造——以川东北地区长兴组-飞仙关组气藏为例   总被引：20，自引：0，他引：20       下载免费PDF全文

杜春国  郝芳  邹华耀  张俊  朱扬明  王存武 《地质学报》2007,81(1):119-126

目前在川东北地区长兴组—飞仙关组已发现普光、渡口河、铁山坡、罗家寨等多个高含H2S的大、中型气田。通过天然气地球化学特征、流体包裹体盐度和岩心及薄片的镜下详细观察后认为,川东北地区长兴组—飞仙关组的大多数气藏遭受了热化学硫酸盐还原作用(TSR)的化学改造,TSR的改造主要表现在3个方面:1使C2 重烃相对于CH4、12C相对于13C优先被消耗,造成天然气干燥系数变大和碳同位素变重;2由于TSR产生的大量淡水的加入,使气藏的原生地层水被稀释,造成地层水盐度降低;3TSR相关流体(烃类和H2S等)与储层岩石之间的相互作用使储层被溶蚀和硬石膏发生蚀变,造成储层孔隙度增大,从而对改善其物性具有重要意义。  相似文献   

Indian Ocean tsunamis: environmental and socio-economic impacts in Langkawi, Malaysia     

MICHAEL BIRD  SUSAN COWIE  REA HAWKES†  BEN HORTON†  COLIN MACGREGOR  JIN EONG ONG‡  AILEEN TAN SHAU HWAI§  TEH TIONG SA¶  ZULFIGAR YASIN§ 《The Geographical journal》2007,173(2):103-117

We report the results of a study of the physical characteristics and socio-economic impacts of the Indian Ocean Tsunami of 26 December 2004 on the tourist island of Langkawi, Malaysia. In comparison with many other locations struck by the tsunami, the immediate physical and socio-economic impacts in Langkawi were relatively minor. A detailed survey of the watermark and ground elevations was undertaken in the worst affected area between Sungei Kuala Teriang and Sungei Kuala Melaka. Here, the tsunami reached a maximum elevation of 4.29 m as it crossed the coast, with a maximum flow depth of 2.0 m and a very consistent run-up elevation relative to mean sea level of 300 ± 10 cm. The tsunami inundated inshore areas for 300 m and penetrated inland along creeks for 500–1000 m. Structural damage to buildings was confined to within 50–150 m of the shoreline where about 10% of the houses were completely destroyed and 60–70% suffered significant structural damage. Damage was particularly severe in areas where there was no engineered coastal protection, but while coastal revetments did provide enhanced protection for houses at the waterfront, the coastline in the study area appeared to be more heavily impacted than elsewhere in Langkawi because wave energy was focused on the area by offshore breakwaters built to protect the Langkawi port and airport. Emergency response after the tsunami was rapid and efficient but would have been improved if the local police station had not been rendered inoperative by the first wave, and if a mechanism had been in place to ensure that informal advance warnings transmitted between Phuket (Thailand), Langkawi and Penang (Malaysia) by tourist operators could have been more widely disseminated.  相似文献   

Non-linear seismic behavior of structures with limited hysteretic energy dissipation capacity   总被引：1，自引：0，他引：1  

Pierino Lestuzzi  Youssef Belmouden  Martin Trueb 《Bulletin of Earthquake Engineering》2007,5(4):549-569

This paper investigates the non-linear seismic behavior of structures such as slender unreinforced masonry shear walls or precast post-tensioned reinforced concrete elements, which have little hysteretic energy dissipation capacity. Even if this type of seismic response may be associated with significant deformation capacity, it is usually not considered as an efficient mechanism to withstand strong earthquakes. The objective of the investigations is to propose values of strength reduction factors for seismic analysis of such structures. The first part of the study is focused on non-linear single-degree-of-freedom (SDOF) systems. A parametric study is performed by computing the displacement ductility demand of non-linear SDOF systems for a set of 164 recorded ground motions selected from the European Strong Motion Database. The parameters investigated are the natural frequency, the strength reduction factor, the post-yield stiffness ratio, the hysteretic energy dissipation capacity and the hysteretic behavior model (four different hysteretic models: bilinear self-centring, with limited or without energy dissipation capacity, modified Takeda and Elastoplastic). Results confirm that the natural frequency has little influence on the displacement ductility demand if it is below a frequency limit and vice versa. The frequency limit is found to be around 2 Hz for all hysteretic models. Moreover, they show that the other parameters, especially the hysteretic behavior model, have little influence on the displacement ductility demand. New relationships between the displacement ductility demand and the strength reduction factor for structures having little hysteretic energy dissipation capacity are proposed. These relationships are an improvement of the equal displacement rule for the considered hysteretic models. In the second part of the investigation, the parametric study is extended to multi-degree-of-freedom (MDOF) systems. The investigation shows that the results obtained for SDOF systems are also valid for MDOF systems. However, the SDOF system overestimates the displacement ductility demand in comparison to the corresponding MDOF system by approximately 15%.  相似文献   

土钉支护弹塑性数值分析及稳定性探讨   总被引：12，自引：5，他引：12  

连镇营  韩国城  吕凯歌 《岩土力学》2002,23(1):85-89

用三维弹塑性有限元法对土钉支护进行了边开挖、边安装土钉和喷射混凝土面层的施工过程的数值模拟分析。通过一种强度折减技术探讨了土钉支护的稳定性。研究结果表明，施工过程中在不同的使用荷载作用下受力最大的土钉并不是一成不为的，因此，在土钉支护工程中不能随意地缩短某层土钉的长度。数值计算确定的潜在滑裂区和局部破坏区符合实际情况，认为钉体拔出是土钉支护最可能出现的内部失稳形式。  相似文献   

Inelastic buildings with tuned mass dampers under moderate ground motions from distant earthquakes     

P. Lukkunaprasit  A. Wanitkorkul 《地震工程与结构动力学》2001,30(4):537-551

The effectiveness of tuned mass dampers (TMD) in vibration control of buildings was investigated under moderate ground shaking caused by long‐distance earthquakes with frequency contents resembling the 1985 Mexico City (SCT) or the 1995 Bangkok ground motion. The elastic–perfectly plastic material behaviour was assumed for the main structure, with linear TMDs employed by virtue of their simplicity and robustness. The accumulated hysteretic energy dissipation affected by TMD was examined, and the ratio of the hysteretic energy absorption in the structure with TMD to that without it is proposed to be used, in conjunction with the peak displacement ratio, as a supplementary TMD performance index since it gives an indication of the accumulated damage induced in the inelastic structures. For the ground motions considered, TMD would be effective in reducing the hysteretic energy absorption demand in the critical storeys for buildings in the 1.8–2.8 s range. The consequence is reduction in damage of the buildings which would otherwise suffer heavy damage in the absence of TMD, resulting in economical restorability in the damage control limit state. This is of practical significance in view of the current trend toward performance‐based design. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

Trace Elements Analysis of Geological Samples by Laser Ablation Inductively Coupled Plasma Mass Spectrometry     

Luo Yan Liu Yongsheng Hu Shenghong Gao Shan Open Laboratory of Constitution  Interaction  Dynamics of the Crust Mantle System  Ministry of National Lands  Resources  China University of Geosciences  Wuhan Lin Shoulin Faculty of Material Sc 《中国地质大学学报(英文版)》2001,12(3)

ＩＮＴＲＯＤＵＣＴＩＯＮＬａｓｅｒａｂｌａｔｉｏｎｉｎｄｕｃｔｉｖｅｌｙｃｏｕｐｌｅｄｐｌａｓｍａｍａｓｓｓｐｅｃｔｒｏｍｅ ｔｒｙｉｓａｎｉｎｃｒｅａｓｉｎｇｌｙｄｅｖｅｌｏｐｅｄａｎａｌｙｔｉｃａｌｔｅｃｈｎｉｑｕｅｆｏｒｓｏｌｉｄｓａｍｐｌｅａｎａｌｙｓｉｓ.ＬＡ ＩＣＰ ＭＳｏｆｆｅｒｓａｔｔｒａｃｔｉｖｅｃｈａｒａｃｔｅｒｉｓｔｉｃｓｏｆｈｉｇｈｓｅｎｓｉｔｉｖｉｔｙ ,ｌｏｗｄｅｔｅｃｔｉｏｎｌｉｍｉｔｓ,ｍｉｎｉｍａｌｓａｍｐｌｅｐｒｅｐａｒａ ｔｉｏｎ ,ｌｅｓｓｏｘｉｄｅｓｉｎｔｅｒｆｅ…  相似文献   

新疆头屯河流域水沙特性与减沙治理   总被引：2，自引：0，他引：2  

陈亚宁  汪雄祥 《干旱区地理》1996,19(2):37-43

本文通过对头屯河流域山区各水文实测水文，泥沙资料的分析比较，揭示了头屯河水沙运移规律，指出了头屯河上游产水，中游产沙，水沙异源的特点，进而地实才考察测量的基础上，结合流域自然特点，提出了工程，生物措施相结合的减沙治理方案和在流域不同地段的具本治理措施。  相似文献   

鄂东铅锌矿床成矿中磷酸盐生物和非生物还原作用的有机地球化学研究     

胡明安  罗学常  高广立 《地球学报》1996,17(Z1):97-103

矿床产于三叠系大冶群碳酸盐岩中，有机质来自海相浮游生物和微生物。矿层中有机质发生成熟异常，已达过成熟作用早期。这得到镜质体反射率（Ro达4.6%）和矿物包裹体测温（均—温度达210℃）的证实。部分标本中有机质被微生物降解。硫同位素δ34S值大部分为正值，小部分为负值。综合研究表明在鄂东铅锌硫化物矿床的形成过程中，硫酸盐的生物和非生物还原作用，均具有十分重要的成矿意义。  相似文献   

国家地震局地震工程代表团赴美访问     

The Earthquake Engineering Delegation of SSB 《国际地震动态》1993,(3):12-16

  相似文献