1800—1813年上海地区梅雨特征和汛期降水量的复原

私人日记是重建高分辨率历史天气气候序列的珍贵史料来源。以《查山学人日记》中的雨日记录为指标复原了日记史料相对缺乏的19世纪早期(1800—1813年)上海地区的梅雨特征,并将雨日区分为5个降水等级,同时将1951—1998年上海龙华站器测日降水量划分为与日记降水记录相匹配的5个降水等级,然后根据龙华站梅雨期、汛期各级雨日数与降水量之间的回归关系复原了1800—1813年的梅雨量和汛期降水量。结果显示:(1)1800—1813年的梅雨相对典型,平均入梅日期为6月10日,出梅日期7月7日,梅期雨日数20.1天,梅期长度27.1天,梅雨量257.3 mm,汛期降水量669.5 mm,与利用《雨雪分寸》重建的梅雨期大体一致,梅雨量有较大差异。(2)整体上看,该时段平均入、出梅日期比龙华站各年代有所提前,梅期雨日数和长度略有增加,梅雨量偏丰,梅雨强度偏强,汛期降水量在适中水平。梅雨特征量、汛期降水量与龙华站各年代不存在显著差异,与20世纪80、90年代最相近。(3)复原的“梅期雨日数、梅期长度”、汛期降水量与区域旱涝状况均有较好的对应关系,与东亚夏季风强弱变化指示的降水空间变化特征也比较相符,反映出文中所用的日记资料以及复原方法和结果具有较高的可靠性。     

OSL dating of the AD 869 Jogan tsunami deposit,northeastern Japan

Sediments deposited by the AD 869 Jogan tsunami offer an opportunity to test the reliability of optically stimulated luminescence (OSL) dating of relatively old historical tsunami deposits. We collected a geoslicer sample from sand deposited on the Sendai Plain, northeastern Japan, by the Jogan tsunami and applied quartz OSL dating to it. We then compared the OSL ages with the known age of the tsunami event. In ascending order, the sedimentary sequence in the geoslicer sample consists of the beach–dune sand, lower peat, Jogan tsunami deposit, upper peat, pre-2011 paddy soil, and the 2011 tsunami deposit. To obtain equivalent dose (D_e,bulk), a standard single-aliquot renegerative-dose (SAR) protocol was applied to large aliquots of the 180–250 μm fraction of two samples from the beach–dune sand, and four samples from differing levels of the Jogan tsunami deposit. The OSL decay curves were dominated by the medium component; thus, for two samples from the Jogan deposit the fast-component OSL signal was isolated and used to determine the equivalent dose (D_e,fast). Using D_e,bulk, OSL ages of the tsunami deposit were underestimated by ∼40%, and even the beach–dune sand was dated younger than AD 869. In contrast, D_e,fast provided a robust age estimate with only slight underestimation. A pulse annealing test showed that the bulk and medium-component OSL signals were thermally unstable. The medium component in the natural OSL was clearly truncated in comparison to the regenerated OSL; the medium component is thus considered to be the main cause of the underestimated ages. Similar effects of a dominant medium-component OSL have been reported in tectonically active regions, which are also prone to tsunamis. The effect of this dominance should be carefully considered in quartz OSL dating of tsunami deposits.     

1960年以来青海湖沉积物粒度的时空分布及其控制因素

对大型湖泊盆地沉积物粒度组成进行研究，有助于解读全球致密油气和页岩油气勘探开发与其记录的古气候信息。 文章对青海湖沉积物粒度时空分布进行了详细的研究，通过采集覆盖大部分湖区的27根近现代沉积岩芯，并对湖心的三根 典型沉积岩芯进行了137Cs测定获取沉积岩芯的年龄；基于磁化率地层年龄模式，建立了整个湖区沉积岩芯的年代框架。粒 度分析结果显示，青海湖岩芯沉积物的粒度分布呈多峰，以细颗粒沉积为主，其中粉砂含量60%~70%，粘粒组分为10%~ 35%，砂粒组分低于20%。青海湖沉积物的粒度变化在空间上相对较复杂，中值粒径呈现明显的砂岛附近、西部和西南湖 区高，其他湖区低的特征。在时间上，大体上自1960年到2017年呈现变粗的趋势，砂粒组分增多，粘粒组分减少。这些粒 度的时空变化可能是受风砂活动、流域土壤侵蚀、河流径流变化、湖平面变化和人类活动共同作用而成。     

旅游地理信息系统的初步研究

针对当前旅游业的发展状况,提出如何结合地理信息系统对旅游业的规划和管理进行重新定位,探讨旅游地理信息系统在旅游业的发展前景,进而使旅游业走上健康的道路。     

西藏班戈错近50年来的湖面变化

本文根据大量地形图、遥感图像或遥感数据、连续29个月的水位观测记录、三次水深测量和2003年5 月26日的湖水位高程测量等资料,勾绘了班戈错近50年来的湖岸线变迁和湖面高程变化曲线图。研究表明,自1959 年至2003年9月的近50年间班戈错湖面总体上升,但其间经历了先降后升再略有下降的过程,即自1959年至1973年或稍晚,班戈错一直收缩、湖面下降了0．25 m;自1973年或稍晚至2001年秋,湖面总体上升,其幅度可达1．75 m;其后,湖面又略有下降。班戈错湖面变化的原因难以用其面积较小的流域本身的气温与降水的变化来解释,只能归结为与其有水力联系的母湖色林错流域自1973年起气温的持续上升所引起的主要补给河流扎加藏布源区唐古拉山与巴汝藏布和申扎藏布源区申扎杰岗山的现代冰川的融水释放水量增大使色林错水位上升,因色林错与班戈错之间有一定的水力联系而引起班戈错水位上升。     

Non-volatile vs volatile behaviours of halogens during the AD 79 plinian eruption of Mt. Vesuvius, Italy

Pre-eruptive conditions and degassing processes of the AD 79 plinian eruption of Mt. Vesuvius are constrained by systematic F and Cl measurements in melt inclusions and matrix glass of pumice clasts from a complete sequence of the pumice-fallout deposits. The entire ‘white pumice’ (WP) magma and the upper part of the ‘grey pumice’ (GP) magma were saturated relative to sub-critical fluids (a Cl-rich H₂O vapour phase and a brine), with a Cl melt content buffered at ~ 5300 ppm, and a mean H₂O content of ~ 5%. The majority of the GP magma was not fluid-saturated. From these results it can be estimated that the WP magma chamber had a low vertical extent (< 500 m) and was located at a depth of ~ 7.5 km while the GP magma reservoir was located just beneath the WP one, but its vertical extent cannot be constrained. This is approximately two times deeper than previous estimates. H₂O degassing during the WP eruption followed a typical closed-system evolution, whereas GP clasts followed a more complex degassing path. Contrary to H₂O, Cl was not efficiently degassed during the plinian phase of the eruption.

This study shows that F and Cl behave as incompatible elements in fluid-undersaturated phonolitic melts. H₂O saturation is necessary for a significant partitioning of Cl into the fluid phase. However, Cl cannot be extracted in significant quantity from phonolitic melts during rapid H₂O degassing, e.g. during plinian eruptions, due to kinetics effects. Halogen contents are better preserved in volcanic glass (melt inclusions or matrix glass) than H₂O, therefore the combined analysis of both volatile species is required for reliable determination of pre-eruptive conditions and syn-eruptive degassing processes in magmas stored at shallow depths.     

734年天水7级地震考证与发震构造分析

根据历史地震资料的考证结果,734年天水地震的极震区位于秦州中都督府、麦积都尉一带,今天水市秦城区、北道区和麦积山一带,震中烈度达Ⅹ度,震级71/2级左右。其等震线长轴方向为NW向,大致与西秦岭北缘断裂带的甘谷-武山断裂段相吻合,极震区正好位于甘谷-武山断裂段的东端。综合分析认为,734年天水71/2级地震的发震构造为西秦岭北缘断裂带的甘谷-武山断裂段东端     

榆木山北缘断裂古地震特征研究

榆木山北缘断裂位于祁连山主体山系以北的榆木山北部边缘.断裂活动形成一系列沿山前发育的断层陡坎.通过探槽剖面对发生在该断裂带上的古地震事件进行了分析,大致可以确定全新世以来的2次古地震事件.事件Ⅰ的年代为距今(4.066±0.086)ka;事件Ⅱ为距今(6.852±0.102)ka至(6.107±0.082)ka之间.该...     

相位法激光测距信号源系统研究

为了使相位式激光测距获得更好的调制信号源,采用了基于单片机控制DDA芯片AD9851产生频率可调,相位可控的信号源,由于DDS具有噪声低,频率分辨率高,易于编程等优点,根据实际需要,通过给AD9851编程获得不同的频率,满足不同距离的测量.由于获得的信号源中存在着高频杂散信号,设计了最接近理想特性的椭圆低通滤波器,并给...     

基于Profibus智能化DP从站的温度采集模块的设计

介绍了使用热偶信号调理专用芯片AD595及Profibus总线用于从站的智能通信芯片SPC3,设计智能温度采集模块的方法,该温度采集模块不再需要调零、冷端补偿、电压放大和线性化等繁琐的工作,并可以直接测量热电偶输出的mv级电压信号.