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991.
A PRELIMINARY RESEARCH ON THE RIGHT-LATERAL STRIKE-SLIP CHARACTERISTICS AND THE STRUCTURAL SIGNIFICANCE OF THE NORTHERN KUANTANSHAN FAULTS,HEXI CORRIDER,BASED ON HIGH-RESOLUTION IMAGERY 下载免费PDF全文
The sinistral strike-slip characteristic of the Altyn Tagh Fault gradually disappears near the Jiuxi Basin at the west end of Hexi Corridor, and the Kuantanshan Fault and the northern marginal fault of Heishan on its east are thrust structures. There are two faults distributed in the north of Kuantanshan, namely, the Taerwan-Chijiaciwo Fault and the Ganxiashan Fault, both are featured with obvious activity. Predecessors thought that the Taerwan-Chijiaciwo Fault is a thrust fault with low movement rate, but there is few detailed study on its horizontal motion. Is there horizontal strike-slip movement in the northern marginal fault of Kuantanshan? This issue has an important significance to further explore the structural transformation mode between the Altyn Tagh strike-slip faults and the northern thrust faults in the north margin of Qilianshan. Using high resolution remote sensing images and field work, such as combining with UAV SfM photogrammetry, the paper studies the strike-slip characteristics of the Taerwan-Chijiaciwo Fault and Ganxiashan Fault on the northern margin of Kuantanshan, and get two preliminary understandings:(1) The northern marginal fault of Kuantanshan is an active right-lateral strike-slip fault with thrust component, the horizontal to vertical dislocation ratio is about 3-4 times. Based on the statistics of dislocation amount of the gullies and terraces along the north marginal Kuantanshan fault, it is preliminarily estimated that the late Pleistocene right-lateral strike-slip rate is about 0.2-0.25 mm/a and the Holocene right-lateral strike-slip rate is about 0.5-1.5 mm/a. (2) The main driving force to the tectonics at the western end of Hexi Corridor, where the northern marginal fault of Kuantanshan locates, comes from the northward extrusion of the Qilian Mountains, which results in the right-lateral strike-slip of the northern marginal fault of Kuananshan and the thrust movement of several faults inside the Jiuxi Basin. The effect of the Altyn Tagh Fault on other tectonic structures is not obvious in this region. 相似文献
992.
Cesária Gomes Ana Nobre Silva Rui Taborda Filipe Santos Luís Rebelo Aníbal Medina 《地球表面变化过程与地形》2019,44(14):2810-2822
Beach erosion poses significant threat to small island economies which are generally highly dependent on coastal tourism. This work investigates the evolution of the low-lying sandy coast of Boa Vista through an integrated characterization of coastline and shoreline indicators (over the past four decades) based on aerial imagery. It was found that tandem use of the two indicators was important to obtain a reliable perspective of the Boa Vista low-lying coastal evolution across a wide range of coastal environments. Results indicate that between 1968 and 2010 the coast was relatively stable, although some spatial variability was recognized. The largest changes were observed at the tips of embayed beaches and a clear coastal progradation was found at the southern (downwind) coastal sectors. Coastal evolution has been dominated by sediment budget and the results put in evidence the sedimentary connections between the beaches across the island, either through bypass and overpass processes. Findings show that understanding coastal evolution at low-lying islands should be supported on island-scale observations, being the only scale capable to capture the sedimentary connections between beach systems, that often control coastal evolution. © 2019 John Wiley & Sons, Ltd. © 2019 John Wiley & Sons, Ltd. 相似文献
993.
采用吉林、黑龙江、辽宁和内蒙古地震台网记录的地震波形数据,利用ISOLA近震全波形反演方法对2019年5月18日吉林宁江MS5.1地震进行全矩张量反演。结果表明,该地震的最佳断层面解节面Ⅰ走向304°/倾角81°/滑动角26°,节面Ⅱ走向210°/倾角65°/滑动角170°;最佳矩心深度6km,矩震级MW5.0。根据宁江MS5.1地震序列展布形态,推断节面Ⅱ可能为优势发震断层面,即本次地震的主控断裂为扶余-肇东断裂,和与其正交的第二松花江断裂共同控制着余震展布方向。全矩张量解在Husdon震源类型图上的投影显示本次地震具有明显的非双力偶成分,是1次体积增加的张性破裂。根据区域地质构造特征和震源区接收函数、电磁测深和地下热结构等地球物理研究结果,综合分析认为在西太平洋板块作用形成俯冲带的同时,也相应地产生了热物质上涌,这些地球物理过程可能会改变莫霍面形态,使其向上突起并作用于活动断层,从而形成此次吉林宁江MS5.1地震。 相似文献
994.
995.
Weiping Jiang Yifang Ma Xiaohui Zhou Zhao Li Xiangdong An Kaihua Wang 《Journal of Seismology》2017,21(6):1599-1612
This paper studies ionospheric vertical total electron content (VTEC) variations before the 1 April 2014 Mw 8.2 Chile earthquake. VTEC derived from 14 global positioning system (GPS) stations and global ionospheric map (GIM) were used to analyze ionospheric variations before the earthquake using the sliding interquartile range method, and the results showed that significant positive VTEC anomalies occurred on 28 March. To explore possible causes of these anomalies, effects of solar and geomagnetic activities were examined, and VTEC variations during 17 March to 31 March in 2009–2013 were cross-compared. Also, VTEC for a full year before the earthquake was investigated. The results indicated that the anomalies were weakly associated with high solar activities and geomagnetic storms and that the anomalies were not normal seasonal and diurnal variations. An analysis of the spatial distribution of the observed anomalies was also presented, and it demonstrated that the anomalies specifically appeared around the epicenter on 28 March. We suggest that the observed anomalies may be associated with the subsequent Chile earthquake. Equatorial anomaly variations were analyzed to discuss the possible physical mechanism, and results showed that the equatorial anomaly unusually increased on 28 March, which indicates that anomalous electric fields generated in the earthquake preparation area and the meridional wind are possible causes of the observed ionospheric anomalies. 相似文献
996.
Bingqiang Yuan Lijun Song Li Han Shaole An Chunguan Zhang 《Geophysical Prospecting》2018,66(8):1586-1601
The Tobago Basin, which is located offshore northern Venezuela with a southern margin close to Trinidad and Tobago, has an area of approximately 59,600 km2. The Tobago Basin has relatively favourable hydrocarbon prospects, and to date, exploration work has mainly concentrated on small areas of the southwestern portion of the basin. To conduct a comprehensive study of the structural framework of the basin and the characteristics of the basement in order to identify prospective zones for hydrocarbon exploration, shipborne‐measured and satellite‐measured gravity data, shipborne‐measured magnetic data, and aeromagnetic survey data were analysed. A regularisation filtering method was used to separate and obtain regional and residual gravity and magnetic anomalies. Directional gradients of gravity and magnetic anomalies and the total horizontal gradient and vertical second derivative of gravity anomalies were employed to extract information about fault structures. Regression analysis methods were used to determine the basement depth. The geological significance of the gravity and magnetic fields was examined, the structural framework of the basin was assessed, the basement depth was estimated, and favourable hydrocarbon exploration prospects within the basin were identified. The results show that the Tobago Basin contains complex structures consisting mainly of two groups of faults trending in northeasterly and northwesterly directions and that the major northeasterly trending faults control the main structural configuration and depositional system within the basin. The basement of the Tobago Basin has deep rises and falls. It can be divided into the following four secondary tectonic units: the western sub‐basin, the central uplift area, the southern sub‐basin, and the northeastern sub‐basin. The central uplift area and northeastern sub‐basin are most likely to have developed hydrocarbon accumulations and should be targeted for further exploration. 相似文献
997.
菰(Zizania latifolia)是长江中下游流域常见的挺水植物.为了解菰在野外的扩张和退化机制,本研究通过模拟实验分析了不同时期菰幼苗对短期淹没的形态学响应.实验共选择株高36和70 cm两种幼苗,设计不淹没、50%淹没和100%淹没3个处理.研究结果表明:两组菰幼苗地上部分的形态学响应有一定差异.在100%淹没处理下,36 cm幼苗组株高最低,茎粗和最大叶宽均显著低于其他两个处理;而70 cm幼苗组在不淹没处理下株高最低,茎粗和最大叶宽在50%和100%淹没处理下均无显著差异.两组菰幼苗根系的形态学响应也不一致.36 cm幼苗组,100%淹没处理组的所有6个根系指标均与其他两种处理有显著差异;70 cm幼苗组,不淹没处理组的6个根系指标均与其他两种处理有显著差异.随着淹没深度的增加,两组菰幼苗总生物量和根茎比均逐渐下降;但36 cm幼苗组在100%淹没处理下总生物量和根茎比均显著低于其他两个处理,而70 cm幼苗组在50%和100%淹没处理下却无显著差异.综合以上分析,本研究结果表明随着菰幼苗的生长,其对淹没的形态学响应能力增强.本研究结果对长江中下游湖泊菰的生态调控具有重要意义. 相似文献
998.
铁(氢)氧化物介导的溶解性有机质(DOM)和无机磷(DIP)的固定在水生态系统中普遍存在,对碳、磷元素的生物地球化学循环有重要的影响. 铁(氢)氧化物主要通过吸附和共沉淀两种过程固定DOM和DIP,且铁(氢)氧化物、DOM和DIP三者存在复杂的相互作用. 本文主要从铁(氢)氧化物对DOM和DIP的固定,铁(氢)氧化物、DOM和DIP之间的相互影响等方面综述了相关研究进展,梳理了铁(氢)氧化物、DOM和DIP在吸附和共沉淀过程中的相互作用机制与影响因素. DOM的存在会通过占据铁(氢)氧化物表面吸附点位、络合、抑制铁水解沉淀等途径影响铁(氢)氧化物对DIP的固定; 且不同机制与DOM的不同性质如分子大小、芳香组分、羧基官能团含量等有关. 而DIP的存在会改变铁(氢)氧化物对DOM的固定分馏过程,改变溶液中DOM的组分和性质. 在明晰三者相互作用基础上,探讨了铁(氢)氧化物介导的DOM和DIP的固定过程对湖泊内源磷释放和碳埋藏的可能影响,并对未来的研究方向进行了展望. 相似文献
999.
1000.