Volcanic and Scientific Activity at Kick ’em Jenny Submarine Volcano 2001–2002: Implications for Volcanic Hazard in the Southern Grenadines,Lesser Antilles     

Jan?M.?LindsayEmail author  John?B.?Shepherd  Doug?Wilson 《Natural Hazards》2005,34(1):1-24

Kick em Jenny submarine volcano, ~8 km north of Grenada, has erupted at least 12 times since it was first discovered in 1939, making it the most frequently active volcano in the Lesser Antilles arc. The volcano lies in shallow water close to significant population centres and directly beneath a major shipping route, and as a consequence an understanding of the eruptive behaviour and potential hazards at the volcano is critical. The most recent eruption at Kick em Jenny occurred on December 4 2001, and differed significantly from past eruptions in that it was preceded by an intensive volcanic earthquake swarm. In March 2002 a multi-beam bathymetric survey of the volcano and its surroundings was carried out by the NOAA ship Ronald H Brown. This survey provided detailed three-dimensional images of the volcano, revealing the detailed morphology of the summit area. The volcano is capped by a summit crater which is breached to the northeast and which varies in diameter from 300 to 370 m. The depth to the summit (highest point on the crater rim) is 185 m and the depth to the lowest point inside the crater is 264 m. No dome is present within the crater. The crater and summit region of Kick em Jenny are located at the top of an asymmetrical cone which is about 1300 m from top to bottom on its western side. It lies within what appear to be the remnants of a much larger arcuate collapse structure. An evaluation of the morphology, bathymetry and eruptive history of the volcano indicates that the threat of eruption-generated tsunamis is considerably lower than previously thought, mainly because the volcano is no longer thought to be growing towards the surface. Of more major and immediate concern are the direct hazards associated with the volcano, such as ballistic ejecta, water disturbances and lowered water density due to degassing.  相似文献   

Modelling the response of a fishing fleet to changing circumstances, using cautious non-linear optimization     

Shepherd  J. G.; Garrod  D. J. 《ICES Journal of Marine Science》1981,39(3):231-238

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Bistability of the thermohaline circulation identified through comprehensive 2-parameter sweeps of an efficient climate model   总被引：2，自引：0，他引：2  

R. Marsh  A. Yool  T. M. Lenton  M. Y. Gulamali  N. R. Edwards  J. G. Shepherd  M. Krznaric  S. Newhouse  S. J. Cox 《Climate Dynamics》2004,23(7-8):761-777

The effect of changes in zonal and meridional atmospheric moisture transports on Atlantic overturning is investigated. Zonal transports are considered in terms of net moisture export from the Atlantic sector. Meridional transports are related to the vigour of the global hydrological cycle. The equilibrium thermohaline circulation (THC) simulated with an efficient climate model is strongly dependent on two key parameters that control these transports: an anomaly in the specified Atlantic–Pacific moisture flux (F_a) and atmospheric moisture diffusivity (K_q). In a large ensemble of spinup experiments, the values of F_a and K_q are varied by small increments across wide ranges, to identify sharp transitions of equilibrium THC strength in a 2-parameter space (between Conveyor On and Off states). Final states from this ensemble of simulations are then used as the initial states for further such ensembles. Large differences in THC strength between ensembles, for identical combinations of F_a and K_q, reveal the co-existence of two stable THC states (Conveyor On and Off)—i.e. a bistable regime. In further sensitivity experiments, the model is forced with small, temporary freshwater perturbations to the mid-latitude North Atlantic, to establish the minimum perturbation necessary for irreversible THC collapse in this bistable regime. A threshold is identified in terms of the forcing duration required. The model THC, in a Conveyor On state, irreversibly collapses to a Conveyor Off state under additional freshwater forcing of just 0.1 Sv applied for around 100 years. The irreversible collapse is primarily due to a positive feedback associated with suppressed convection and reduced surface heat loss in the sinking region. Increased atmosphere-to-ocean freshwater flux, under a collapsed Conveyor, plays a secondary role.  相似文献   

基于地震数据专家的子午链台站地磁自动化产品系统设计与实现     

陈洪凯  陈传华  张明  赵帝  洒荣利 《地震地磁观测与研究》2021,42(4):195-199

基于对子午链台站地震地磁前兆异常以及地球空间环境变化等研究方向的需求分析,利用网络、大数据、云计算等新技术,结合地震数据专家（DatistEQ）软件,设计子午链台站地磁指数报告自动产出系统。该系统通过低代码、敏捷式开发工作流程,连接不同功能节点,可以实现用户定制化、数据标准化、功能智能化的系统报告产出。通过本地或者云端一键流程化工作,将不同类型的数据发送到科研工作者或其他需求者,简化工作流程,优化数据处理,实现高效率产品产出。  相似文献   

Upper atmospheric temperatures from Doppler line widths—V. Auroral electron energy spectra and fluxes deduced from the 5577 and 6300 Å atomic oxygen emissions     

H.H. Zwick  G.G. Shepherd 《Planetary and Space Science》1973,21(4):605-621

This is a report upon further data obtained from the auroral OI 5577 Å emission with a Wide Angle Michelson Interferometer (WAMI), and upon our first observations made with it on the 6300 Å emission. The method used for converting emission intensities and temperatures to auroral electron fluxes and energy spectra is described. Data for the 5577 Å emission are presented for the (lack of) heating in auroral forms, vertical temperature profiles in aurora, electron flux and energy spectrum variations in pulsating aurora, and a ‘cold’ subvisual auroral arc. Data from the OI 6300 Å emission are presented for the diurnal variation of exospheric temperature and for the thermalization of $\text{O}\text{(}{}^1\text{D)}$ in the F-region.  相似文献   

TritonX-100－5-Br-PADAP光度法测定铜和镍   总被引：2，自引：0，他引：2  

萨木嘎  刘颖  嘎日迪 《岩矿测试》1999,18(4):5

研究了非离子型表面活性剂Ｔｒｉｔｏｎ Ｘ－ １００ 存在下,用５ － Ｂｒ － ＰＡＤＡＰ 光度法测定铜、镍的方法。结果表明：在ｐＨ９ ．０ 的硼砂缓冲介质中,５ － Ｂｒ － ＰＡＤＡＰ 与铜和镍生成紫红色络合物,λＣｕｍ ａｘ ＝ ５７５ ｎｍ ,εＣｕ ＝ １ ．０４ ×１０５ Ｌ·ｍｏｌ－ １·ｃｍ － １ ;λＮｉｍ ａｘ ＝ ５７５ ｎｍ ,εＮｉ ＝ １ ．１４ ×１０５ Ｌ·ｍｏｌ－ １·ｃｍ － １ 。铜和镍的质量浓度分别在０ ～５６０ μｇ／ Ｌ和０ ～４４０ μｇ／ Ｌ符合比尔定律。加入六偏磷酸钠后,由于偏磷酸镍的形成,镍不再与５ － Ｂｒ － ＰＡＤＡＰ 显色,可通过铜及铜镍总量的测定,计算出镍的含量。用该方法实测了钢样中铜和镍的含量,结果与推荐值相符,对铜和镍５ 次测定的ＲＳＤ均小于５ ％ 。  相似文献   

单轴压缩下大理岩的Q值与频率关系的研究          下载免费PDF全文

马丽云  赵建华 《地球物理学报》1990,33(6):689-693

实验采用单轴压缩循环加载方式,在地震频段内测量了莱阳大理岩的品质因数Q值.在频率为0.1-10 Hz范围内,Q值随频率变化是非线性的,而且在5 Hz附近出现峰值.用正弦波和用三角波两种方式加载所获得的Q值与频率关系很相似,并且三角波加载所测得的Q值普遍高于用正弦波加载测得的Q值.疲劳试验结果表明,正弦波循环加载大大降低了岩石的强度,三角波则对岩石强度降低较少.  相似文献   

The effect of lithology on valley width,terrace distribution,and bedload provenance in a tectonically stable catchment with flat‐lying stratigraphy          下载免费PDF全文

Amanda Keen‐Zebert  Mark R. Hudson  Stephanie L. Shepherd  Evan A. Thaler 《地球表面变化过程与地形》2017,42(10):1573-1587

How rock resistance or erodibility affects fluvial landforms and processes is an outstanding question in geomorphology that has recently garnered attention owing to the recognition that the erosion rates of bedrock channels largely set the pace of landscape evolution. In this work, we evaluate valley width, terrace distribution, and bedload provenance in terms of reach scale variation in lithology in the study reach and discuss the implications for landscape evolution in a catchment with relatively flat‐lying stratigraphy and very little uplift. A reach of the Buffalo National River in Arkansas was partitioned into lithologic reaches and the mechanical and chemical resistance of the main lithologies making up the catchment was measured. Valley width and the spatial distribution of terraces were compared among the different lithologic reaches. The surface grain size and provenance of coarse (2–90 mm) sediment of both modern gravel bars and older terrace deposits that make up the former bedload were measured and defined. The results demonstrate a strong impact of lithology upon valley width, terrace distribution, and bedload provenance and therefore, upon landscape evolution processes. Channel down‐cutting through different lithologies creates variable patterns of resistance across catchments and continents. Particularly in post‐tectonic and non‐tectonic landscapes, the variation in resistance that arises from the exhumation of different rocks in channel longitudinal profiles can impact local base levels, initiating responses that can be propagated through channel networks. The rate at which that response is transmitted through channels is potentially amplified and/or mitigated by differences between the resistance of channel beds and bedload sediment loads. In the study reach, variation in lithologic resistance influences the prevalence of lateral and vertical processes, thus producing a spatial pattern of terraces that reflects rock type rather than climate, regional base level change, or hydrologic variability. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

Crustal deformation and tectonic levels of Nujiang Gorge since the Miocene     

LIU ZhiCheng  JI JianQing  SA Xiao  CHEN YaPeng  ZHONG DaLai 《中国科学:地球科学(英文版)》2018,(1)

Crustal deformation shows different patterns at different depths due to changes in the physical properties of rock.Tectonic levels can be defined based on the geometry and deformation mechanisms of crustal deformation patterns. Nujiang Gorge, with a high riverbed drop, great erosion depth, and strong deformation, has rock exposures at different tectonic levels and thus provides an ideal lab for deformation study. This paper takes the Nujiang Gorge from Chawalong to Fugong as the object to identify structural deformation patterns at different depths through field study and deformation analysis. At depth, the primary form of deformation is flow deformation, as shown on the outcrops at Maji. Ductile shear deformation can be found in many outcrops within the study region, e.g., the Gaoligong dextral shear zone and Puladi-Songta sinistral shear zone that lie to the south and north of Maji, respectively. Further to the north of Puladi, the dominated deformation pattern is similar fold and dense sub-vertical foliation. In addition, brittle faults, as evidence of shallow deformation, can be seen overprinting on the deeper deformation features all over the region. Based on those observations, this paper identifies four tectonic levels from depth to the surface: flow deformation, ductile shear deformation, similar fold, and brittle fault deformation, all of which result from the NEE-SWW compressive stress field. Further evidence from studies on the region′s thermal evolution and regional tectonics suggests that the development of different tectonic levels is closely linked to the discrepant uplift or denudation since the Miocene(~21 Ma).  相似文献   

2000-2013年浑善达克沙地植被净初级生产力变化研究     

元志辉  池勇峰  雷军  包刚  包玉海  萨楚拉  咏梅 《冰川冻土》2017,39(1):185-199

利用卫星遥感资料和地面气象观测资料,基于CASA模型及其他数理方法估算了浑善达克沙地2000-2013年生长季（4-10月）植被净初级生产力（NPP）,并对其时空变化特征进行了分析,讨论了气候因子和人类活动对植被净初级生产力的影响。结果表明： 14年间,研究区生长季的植被净初级生产力呈波动中增加趋势,多年平均NPP为239.8 gC·m^-2·a^-1。整个研究区表现为高NPP值（大于150 gC·m^-2·a^-1）的植被面积在增加,低NPP值（小于150 gC·m^-2·a^-1）的植被面积在减少。在空间分布上,研究区的北部、中部和南部边缘区域的植被NPP增加趋势较明显,而东部和西部部分区域未发生明显的趋势性变化。总体而言,研究区植被净初级生产力变化趋势与降水量的关系更密切,其相关系数达到0.86,是驱动植被NPP年际波动的最直接因素。而与温度呈负相关,相关系数为-0.42。综合考虑气候因素和人类活动对沙地NPP的影响发现,温度降低、种饲料面积、年末牲畜存栏头数和羊的数量的减少是NPP值提高的关键因素。  相似文献