Movement of tidal watersheds in the Wadden Sea and its consequences on the morphological development     

Z.B.WANG  J.VROOM  B.C.van PROOIJEN  R.J.LABEUR  M.J.F.STIVE 《国际泥沙研究》2013,28(2):162-171

The Wadden Sea consists of a series of tidal lagoons which are connected to the North Sea by tidal inlets. Boundaries of each lagoon are the mainland coast, the barrier islands on both sides of the tidal inlet, and the tidal watersheds behind the two barrier islands. Behind each Wadden Island there is a tidal watershed separating two adjacent tidal lagoons. The locations of the tidal watersheds in the Wadden Sea are not fixed. Especially after a human interference in one of the tidal lagoons, a tidal watershed can move and thereby influence the distribution of area between the lagoons. This appears to be important for the morphological development in not only the basin in which the interference takes place, but also in the adjacent basins. This paper describes theoretical analyses and numerical modelling aimed at improving the insights into the location of the tidal watersheds, their movements, and the impact of the movements of tidal watersheds on the morphological development of a multi-basin system like the Wadden Sea.  相似文献   

The large aftershocks triggered by the 2011 Mw 9.0 Tohoku-Oki earthquake,Japan     

《Journal of Asian Earth Sciences》2013

The Mw 9.0 Tohoku-Oki earthquake that occurred off the Pacific coast of Japan on March 11, 2011, was followed by thousands of aftershocks, both near the plate interface and in the crust of inland eastern Japan. In this paper, we report on two large, shallow crustal earthquakes that occurred near the Ibaraki-Fukushima prefecture border, where the background seismicity was low prior to the 2011 Tohoku-Oki earthquake. Using densely spaced geodetic observations (GPS and InSAR datasets), we found that two large aftershocks in the Iwaki and Kita-Ibarake regions (hereafter referred to as the Iwaki earthquake and the Kita-Ibarake earthquake) produced 2.1 m and 0.44 m of motion in the line-of-sight (LOS), respectively. The azimuth-offset method was used to obtain the preliminary location of the fault traces. The InSAR-based maximum offset and trace of the faults that produced the Iwaki earthquake are consistent with field observations. The fault location and geometry of these two earthquakes are constrained by a rectangular dislocation model in a multilayered elastic half-space, which indicates that the maximum slips for the two earthquakes are 3.28 m and 0.98 m, respectively. The Coulomb stress changes were calculated for the faults following the 2011 Mw 9.0 Tohoku-Oki earthquake based on the modeled slip along the fault planes. The resulting Coulomb stress changes indicate that the stresses on the faults increased by up to 1.1 MPa and 0.7 MPa in the Iwaki and Kita-Ibarake regions, respectively, suggesting that the Tohoku-Oki earthquake triggered the two aftershocks, supporting the results of seismic tomography.  相似文献   

矿井地质灾害要素与地质灾源体辨识评价     

夏玉成  王锐  马丽 《中国煤炭地质》2019,(2):51-55

矿井地质灾害严重威胁人民生命财产安全,深入认识成灾机理与相关要素,准确辨识地质灾源体并评价其致灾危险度,是煤矿防灾减灾保障安全开采不可或缺的基础性工作。本文通过分析矿井地质灾害典型案例,认为矿井地质灾源体是在煤矿采掘过程中具有发生矿井地质灾害潜在危险的地质体,包括煤层及其围岩以及存在其中的地下水与瓦斯等,具有地源性、隐蔽性、触发性、可控性等主要特征;矿井地质灾源体是矿井地质灾害的内因,煤矿采掘活动是触发矿井地质灾害的外因,地质影响因素和人为影响因素可能提高或降低矿井地质灾害的危险程度;并提出了辩识地质灾源体和评价其致灾危险度的具体方法。  相似文献   

Sea Level Changes Along Bangladesh Coast in Relation to the Southern Oscillation Phenomenon   总被引：1，自引：1，他引：0  

O. P. Singh Tariq Masood Ali Khan  Tad S. Murty  Md. Sazedur Rahman 《Marine Geodesy》2013,36(1):65-72

Interannual variations of sea level along the Bangladesh coast are quite pronounced and often dominate the long-term sea level trends that are taking place. The El Niño/Southern Oscillation (ENSO) induced variation is an important component of interannual mode of variations. The present article deals with the relationship between the sea level variations along the Bangladesh coast and the Southern Oscillation phenomenon. The mean tide level data of monsoon season (June to September) pertaining to Hiron Point (in Sundarbans) and Char Changa (on the mouth of Meghna River) have been analyzed and correlated to the Southern Oscillation Index (SOI). The annual variation of mean tide level in the coastal areas of Bangladesh reveals that the tide level reaches its peak during the monsoon season. The maximum tide level during the calendar year is recorded in August. Thus, it is not surprising that the inundation of the coastal belt of Bangladesh due to the floods is most common during the summer monsoon season, especially from July to September. Therefore, the sea level variations during the monsoon are of paramount importance to Bangladesh. The results of the present study show that both at Hiron Point and Char Changa there is a substantial difference between the mean tide level during the El Niño and La Niña monsoons. The mean tide level at Hiron Point is higher by about 5 cm during August of La Niña years as compared to that during the El Niño years. The difference at Char Changa, which is located at the mouth of Meghna River, is much higher. This is probably due to the increased fresh water discharge into the Meghna River during La Niña years. Thus at the time of crossing of a monsoon depression, the chances of widespread inundation are higher during a La Nin~a year as compared to that during an El Niño year. The Correlation Coefficients (CCs) between Mean Tide Levels (MTLs) at Hiron Point and Char Changa and the SOI during September (at the end of monsoon) are +0.33 and +0.39 respectively. These CCs are statistically significant at 90% and 95% levels, respectively. These results may find applications in the preparedness programs for combating sea level associated disasters in Bangladesh.  相似文献   

An Improved Calibration of Satellite Altimetric Heights Using Tide Gauge Sea Levels with Adjustment for Land Motion     

Gary T. Mitchum 《Marine Geodesy》2013,36(3):145-166

Several major improvements to an existing method for calibrating satellite altimeters using tide gauge data are described. The calibration is in the sense of monitoring and correcting temporal drift in the altimetric time series, which is essential in efforts to use the altimetric data for especially demanding applications. Examples include the determination of the rate of change of global mean sea level and the study of the relatively subtle, but climatically important, decadal variations in basin scale sea levels. The improvements are to the method described by Mitchum (1998a), and the modifications are of two basic types. First, since the method depends on the cancellation of true ocean signals by differencing the altimetric data from the tide gauge sea level time series, improvements are made that produce a more complete removal of the ocean signals that comprise the noise for the altimetric drift estimation problem. Second, a major error source in the tide gauge data, namely land motion, is explicitly addressed and corrections are developed that incorporate space-based geodetic data (continuous GPS and DORIS measurements). The long-term solution, having such geodetic measurements available at all the tide gauges, is not yet a reality, so an interim solution is developed. The improved method is applied to the TOPEX altimetric data. The Side A data (August 1992?February 1999) are found to have a linear drift component of 0.55 + / 0.39 mm/yr, but there is also a significant quadratic component to the drift that is presently unexplained. The TOPEX Side B altimeter is estimated to be biased by 7.0 + / 0.7 mm relative to the Side A altimeter based on an analysis of the first 350 days of Side B data.  相似文献   

Mean Sea Level Variation in the South China Sea from Four Decades of Tidal Records in Hong Kong     

H. Baki Iz  C. K. Shum 《Marine Geodesy》2013,36(4):221-233

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Absolute Calibration of the TOPEX/POSEIDON Altimeters using UK Tide Gauges,GPS, and Precise,Local Geoid-Differences     

Xiaojun Dong  Philip Woodworth  Philip Moore  Richard Bingley 《Marine Geodesy》2013,36(3):189-204

This article describes an "absolute" calibration of TOPEX/POSEIDON (T/P) altimeter bias using UK tide gauges equipped with Global Positioning System (GPS) receivers. The method is an extension of earlier work using the Newhaven tide gauge in the English Channel. However, the present analysis extends the research to a number of gauges around the UK and incorporates several improvements. The time-averaged TOPEX and POSEIDON biases are obtained with a precision of approximately 2 and 3 cm, respectively. The research complements work on bias determination by other groups in the T/P Science Working Team and can, in principle, be applied at other locations for which precise, local geoid-differences are available. The relatively sparse POSEIDON data set has been used as a test of our ability to perform an absolute calibration of upcoming Jason-1 altimetry as soon as possible after launch.  相似文献   

汶川地震余震活动固体潮调制的统计分析   总被引：1，自引：1，他引：0  

李金  蒋海昆 《中国地震研究》2013,27(1):23-38

A statistical analysis on the Wenchuan aftershock activity triggered by tidal forces is systematically studied based on Schusters test, including earthquakes triggered by tidal force, tidal stress and tidal coulomb failure stress. The results show that a group of strong aftershocks which occurred at the end of July to early August in 2008 at the north of Wenchuan were obviously triggered by earth tide, the same conclusion is drawn by Schusters smooth test of the tidal force, tidal stress and tidal coulomb failure stress. In addition, the Wenchuan aftershock activity is obviously triggered by fortnight tide. In the north, the aftershocks happened more frequently in the first and last quarters of the moon, and in the south, the aftershocks happened more frequently in the first and last quarters of the moon and during the full moon.  相似文献   

Simulated effect of soil depth and bedrock topography on near‐surface hydrologic response and slope stability     

Cristiano Lanni  Jeff McDonnell  Luisa Hopp  Riccardo Rigon 《地球表面变化过程与地形》2013,38(2):146-159

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基于LXI总线的接口转换器的设计     

孙大雷  王天宝 《成都信息工程学院学报》2008,23(1):8-11

LXI是安捷伦公司和VXI科技公司联合提出的一种新型仪器接口规范,它最大的特点是基于以太网技术,可满足于组建网络化测试系统,是新一代总线标准的代表。介绍了LXI总线的产生以及技术特点,提出一种基于LXI总线协议的接口转换器的设计方案,详细说明了硬件的设计、触发方式的选择、接口驱动及模块间的通信。  相似文献