Factors influencing the recession rate of Niagara Falls since the 19th century

The rate of recession of Niagara Falls (Horseshoe and American Falls) in northeastern North America has been documented since the 19th century; it shows a decreasing trend from ca. 1 m y^− 1 a century ago to ca. 0.1 m y^− 1 at present. Reduction of the flow volume in the Niagara River due to diversion into bypassing hydroelectric schemes has often been taken to be the factor responsible, but other factors such as changes in the waterfall shape could play a role and call for a quantitative study. Here, we examine the effect of physical factors on the historically varying recession rates of Niagara Falls, using an empirical equation which has previously been proposed based on a non-dimensional multiparametric model which incorporates flow volume, waterfall shape and bedrock strength. The changes in recession rates of Niagara Falls in the last century are successfully modeled by this empirical equation; these changes are caused by variations in flow volume and lip length. This result supports the validity of the empirical equation for waterfalls in rivers carrying little transported sediment. Our analysis also suggests that the decrease in the recession rate of Horseshoe Falls is related to both artificial reduction in river discharge and natural increase in waterfall lip length, whereas that of American Falls is solely due to the reduction in flow volume.     

1993年8月8日关岛地震前后ULF磁场异常变化

给出了1993年8月8日关岛地震(Ms=7.1,深度60km)前后ULF(Ultra Low Frequency:超低频信号,频段为O.005～10Hz)地磁信号的分析结果.ULF观测系统位于日本关岛,距离震中约65km.对观测数据进行分析后得出以下结论:①建议用非常细致的统计分析(月均值,标准偏差)来判断ULF信号的强度和极化值(比如:Z/H比值);②ULF信号活动强度和∑Kp的对比,有助于区别空间地磁脉动和非空间源地磁辐射;③发现Z/H比值的使用在把可能来自震源的辐射从空间等离子波中识别出来非常重要;④从对极化值的时间序列的统计分析发现极化值在震前仅一个月时有一个显著的增强,表明这期间的电磁异常现象很可能是震磁前兆信号;⑤Z分量的时间变化类似于Loma Prieta地震前的变化,即在震前10天到两周有明显的增强,在震前几天出现另一次增强;⑥可能与地震有关的电磁辐射是一种类似噪音的自然现象,它们的主要频带范围0.02～0.05Hz(最大幅值约为0.1nT).     

岩石层—大气层—电离层耦合作为震前大气层和电离层短临事件的影响机制

介绍了大气层和电离层震前现象机制的基本观念。简短回顾了观测结果后,我们得出结论：1．流体下层物质（气泡）向上迁移能导致近地表的热水／气体被逐出,并在强度弱化的地区引发地震;2．因此,气泡出现的时间和地点是随机的,但是地震、地球化学异常和前震（地震、SA和超低频电磁异常）是随机关联的;3．大气温度和密度扰动跟随着震前热水／气体释放,导致产生周期为6～60min的大气重力波（AGW）;4．地震引发的大气重力波能导致电离层扰动变化并导致大气层中地平线上无线电波传播、下部电离层低频波扰动和地面超低频辐射衰减的变化。     

与地震有关的电离层扰动的甚低频/低频无线电探测

近期人们认识到,电离层对地震影响非常敏感,探测与地震有关的电离层扰动看来对地震短临预测是非常有前途的。我们提出可利用甚低频／低频（3～30kHz／30-300kHz）无线电探测进行地震-电离层扰动的探测。1995年神户地震明显发现电离层扰动现象之后,开始了利用低电离层甚低频／低频传播信号进行地震短临预测的简短历史。在说明先前的甚低频／低频结果之后,我们给出了最新的甚低频／低频发现：一个是电离层扰动与地震在统计上相关,第二个是2004年12月苏门答腊地震的实例研究,说明了这次地震电离层扰动的空间尺度和动力学原理。     

Field experiments on remediation of coastal sediments using granulated coal ash

Field experiments were carried out to evaluate the effect of Granulated Coal Ash (GCA) on remediation of coastal sediments in terms of removing phosphates and hydrogen sulfide. Phosphate concentrations in the sediment were kept below 0.2 mg/l after the application of GCA, whereas those in the control sites increased up to 1.0 mg/l. The concentration of hydrogen sulfide in the sediment was maintained at almost zero in the experimental sites (GCA application sites) for over one year, whereas it ranged 0.1–2.4 mg S L⁻¹ in control sites. Meanwhile, individual number of benthos increased in the experimental sites by several orders of magnitude compared to the control sites. The major process involved in hydrogen sulfide removal by GCA was thought to be the increase in pH, which suppresses hydrogen sulfide formation. From our findings, we concluded that GCA is an effective material for remediating organically enriched coastal sediment.     

Utilization of laser range finder and differential GPS for high‐resolution topographic measurement at Hacituğrul Tepe,Turkey

Topographic maps are fundamental for geoarchaeological field studies and archaeological excavations. However, traditional methods of topographic mapping, as well as modern high‐tech methods such as airborne laser scanning and photogrammetry of high‐resolution satellite images, are often cost‐ineffective for field studies in terms of time, money, and labor. We here propose a method to measure topography for archaeological sites and surrounding areas quickly and accurately, using a laser range finder (LRF) and differential global positioning system DGPS. Three‐dimensional coordinates of points on land surfaces are measured through the LRF, targeted from multiple measuring locations whose positions are acquired with the DGPS. The point data are then interpolated to produce a digital elevation model (DEM) using a geographic information system (GIS). High‐resolution DEMs can be obtained with this method, with horizontal and vertical accuracies on the order of 10 cm. We here demonstrate the method for measuring detailed topography of the Hacituğrul Tepe in central Turkey. Digital topography data incorporated in GIS can also be part of an archaeological database, providing opportunities for quantitative analyses of topography and archaeological materials. © 2009 Wiley Periodicals, Inc.     

The ultra-low-frequency magnetic disturbances associated with earthquakes

The ultra-low-frequency (ULF) electromagnetic emission is recently recognized as one of the most promising candidates for short-term earthquake (EQ) prediction. This paper reviews previous convincing evidence on the presence of ULF emissions before three major EQs. Then, we present further statistical study on the ULF occurrence, our networks of ULF monitoring in different spatial scales in Japan and finally we present several signal processings to identify the seismogenic emissions by showing latest results for recent large EQs.     

Iron K-emission line from Cygnus X-2

The iron K-emission line of Cyg X-2 was detected from the TENMA observation. The centre energy, the equivalent width and the intrinsic line width are 6.7 keV, 30 eV, and less than 0.6 keV, respectively. These properties indicate that the observed line is mostly due to helium-like iron and the electron scattering depth of the line emitting region is smaller than three.Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984.     

Astronomy in Japan

The research activity in Japanese astronomy is described, taking into account the social and historical background. A trend in the last two decades is shown by the numbers of papers in 13 branches of astronomy. Major research facilities and international collaboration programs are summerized. Future programs under consideration are briefly discussed.Paper presented at the Lembang-Bamberg IAU Colloquium No. 80 on Double Stars: Physical Properties and Generic Relations, held at Bandung, Indonesia, 3–7 June, 1983.