SPECTRUM期间目标台风移动的数值试验   总被引：2，自引：1，他引：2  

罗哲贤  马镜娴  王咏青 《气象学报》1996,54(2):166-174

在目标台风Ｙａｎｃｙ的移动过程中，选择４个时段进行预报数值试验。模式初始场系根据ＳＰＥＣＴＲＵＭ和ＴＣＭ－９０加强观测资料确定。结果表明：实际大气中目标台风移动的若干特征在模式大气中能够显示出来，如Ｙａｎｃｙ在１９９０年８月２０日００时移向的转折现象等；台风非对称结构的低频振荡是产生移向转折现象的一个重要原因。  相似文献   

火山地区二维自然电位异常反演   总被引：2，自引：0，他引：2       下载免费PDF全文

张贵宾 Aubert  M 《地球物理学报》1996,39(6):835-844

将线性反演理论与正则化法相结合，提出一个火山地区二维自然电位（ＳＰ）异常反演方法．地下岩浆活动（对流体）是引起自电异常的极化源，反演的目的是计算地下视极化强度分布和极化源中心位置．可以通过用已知的各种资料改变地下极化源区域（简称源区）的方式来进行多次反演，以便获得一个比较合理的地下视极化强度分布模型．最后，分别给出意大利和墨西哥的两个火山地区的自然电位异常分析结果．  相似文献   

Pyroclastic flows and surges over water: an example from the 1883 Krakatau eruption     

S. Carey  H. Sigurdsson  C. Mandeville  S. Bronto 《Bulletin of Volcanology》1996,57(7):493-511

Pyroclastic deposits from the 1883 eruption of Krakatau are described from areas northeast of the volcano on the islands of Sebesi, Sebuku, and Lagoendi, and the southeast coast of Sumatra. Massive and poorly stratified units formed predominantly from pyroclastic flows and surges that traveled over the sea for distances up to 80 km. Granulometric and lithologic characteristics of the deposits indicate that they represent the complement of proximal subaerial and submarine pyroclastic flow deposits laid down on and close to the Krakatau islands. The distal deposits exhibit a decrease in sorting coefficient, median grain size, and thickness with increasing distance from Krakatau. Crystal fractionation is consistent with the distal facies being derived from the upper part of gravitationally segregated pyroclastic flows in which the relative amount of crystal enrichment and abundance of dense lithic clasts diminished upwards. The deposits are correlated to a major pyroclastic flow phase that occurred on the morning of 27 August at approximately 10 a.m. Energetic flows spread out away from the volcano at speeds in excess of 100 km/h and traveled up to 80 km from source. The flows retained temperatures high enough to burn victims on the SW coast of Sumatra. Historical accounts from ships in the Sunda Straits constrain the area affected by the flows to a minimum of 4x10³ km². At the distal edge of this area the flows were relatively dilute and turbulent, yet carried enough material to deposit several tens of centimeters of tephra. The great mobility of the Krakatau flows from the 10 a.m. activity may be the result of enhanced runout over the sea. It is proposed that the generation of steam at the flow/seawater interface may have led to a reduction in the sedimentation of particles and consequently a delay in the time before the flows ceased lateral motion and became buoyantly convective. The buoyant distal edge of these ash-and steam-laden clouds lifted off into the atmosphere, leading to cooling, condensation, and mud rain.  相似文献   

五大连池火山构造地震空间分布及其构造含义   总被引：3，自引：0，他引：3  

张凤鸣  张守国 《东北地震研究》1996,12(4):17-22

在对五大连池地震台１９８３年以来观测到的五大连池火山区的地震记录复核的基础上，测定了火山构造地震的空间分布状态。研究结果表明该地区地震活动均为壳内地震。受火山构造环境影响，地震活动存在着外围边缘强，震源深度分布深；内部弱，震源深度分布浅的差异。火山区内部地震深度分布优势在５ｋｍ—８ｋｍ，有３个地震分布密集区，震中分布呈明显的沿火山构造断层成带分布特性。在地震条带交汇处，震源深度起伏变化大，是火山构造活动强烈部位  相似文献   

火山气溶胶的辐射影响   总被引：2，自引：1，他引：2  

汪宏七  赵高祥 《大气科学》1992,16(6):755-760

本文应用辐射传输计算研究了火山气溶胶,特别是大的火山爆发后短时期及火山周围地区内的火山气溶胶,对到达地面的向下的总的太阳辐射通量、行星反照率及大气加热率的可能影响.  相似文献   

福建上杭紫金山铜金矿床地质简介   总被引：2，自引：0，他引：2  

姚金炎  彭振安 《矿产与地质》1992,6(2):89-94

以宏观角度介绍紫金山铜金矿床地质背景,论述了火山机构、次火山岩、隐爆角砾岩、围岩及围岩蚀变、矿化带及矿化特征,着重总结该矿床找矿标志,以期在地质找矿中得以借鉴。  相似文献   

浙西北火山岩型铀矿床的成矿条件及成矿规律研究   总被引：2，自引：0，他引：2  

王剑锋 《铀矿地质》1992,(4)

本文根据广泛的野外调查研究和大量的分析统计数据,讨论了浙西北火山岩型铀矿床形成的地质条件和物理化学条件。重点探讨了劳村组、黄尖组和寿昌组的含铀性及岩性、岩相、构造和岩浆活动对成矿的控制作用。探讨了成矿溶液的成分、性质、温度和铀的迁移形式,以及成矿物质来源和成矿机理,并在此基础上总结出铀成矿的时空规律。  相似文献   

滇西墨江西部石炭、二叠纪火山岩   总被引：7，自引：0，他引：7       下载免费PDF全文

周德进  徐平 《地质科学》1992,(3):249-259

墨江西部出露有石炭纪和晚二叠世两套火山岩,它们呈平行的两条带分布。石炭纪火山岩以拉斑玄武岩为主,少量流纹岩,它们是由上地幔源区10%部分熔融形成的原始岩浆,经橄榄石、辉石和斜长石不同程度结晶分异作用形成。其喷发环境可能是一个发育在大陆边缘的张性海盆地。晚二叠世火山岩较为复杂,熔岩与火山碎屑岩交互发育,熔岩主要属于拉斑系列,还含有少量钙碱性系列岩石;形成于陆缘火山弧环境。  相似文献   

Noble gases dissolved in groundwater in a volcanic aquifer: Helium isotopes in the Kumamoto Plain     

Y. Mahara 《Environmental Geology》1995,25(4):215-224

This study Investigates a tracing method using dissolved noble gases to survey the groundwater flow in a large groundwater basin. The tracing method is based on measuring the concentrations of noble gases and the ratio of helium isotopes in groundwater samples. Since it is very difficult to detect trace amounts of noble gases and helium with high accuracy in a 15-ml groundwater sample, dissolved gases were extracted and purified, then a high-resolution mass spectrometer was used for measurement and comparison with standard samples. We used this method with samples from a confined aquifer formed by the deposition of pyroclastic flow in the Kumamoto Plain on the west side of Mt. Aso in central Kyushu, Japan. The groundwater basin under the plain is divided into four small basins, based on the helium concentrations and isotope ratios, with two major groundwater flows. One flow is buried by the Aso pyroclastic flow along the old Kase River; the other is along the Tsuboi River Valley. These two groundwater flows were identified from the different helium isotope-ratios. The helium component from the deep mantle is mixed into the groundwater under the Kumamoto Plain. Finally, data on the concentrations and ratios of³He to⁴He in groundwater samples were used to determine the location of faults in the volcanic aquifer.  相似文献   

Field compaction control studies on road bases in a new settlement area in Ghana     

E. M. Frempong 《Geotechnical and Geological Engineering》1995,13(4):227-241

Summary Among the major causes for failure of roads in the tropics is inadequate compaction during construction. There is, therefore, the need to strictly control the compaction of the pavement layers if the design life of the road is to be attained; thereby eliminating large maintenance costs.This note reports on pavement compaction control studies undertaken on the road bases of service roads in a new settlement area in Ghana. These roads were to be provided with bituminous surfacing immediately after compaction. Studies concerning particle breakdown during field compaction by two contractors executing the works under the same conditions have been made, together with an assessment of contractor efficiency.It was found that the placement moisture contents varied greatly from the optimum. One contractor was compacting the gravels on the dry side of optimum, consequently achieving relatively high densities. The other contractor was compacting on the wet side and achieving lower density levels. This was still the case even after initial test sections were found to have been undercompacted.Compaction levels achieved in the crowns were generally found to be higher than those at the shoulders of the road test sections. The breakdown of coarse particles due to compaction was quite significant. There is therefore the need for highway material engineers to ensure that in addition to meeting the grading requirements, road base materials must adequately meet the requirements on weathering and mechanical strength properties.  相似文献