海岛界定数量的变维分形特征——以嵊泗县为例

我国多次海岛数量普查因界定标准不一而结果相差巨大,为了满足海洋主管部门对海岛的管理要求,亟需研究合理的方法界定海岛数量。利用高分辨率遥感影像解译嵊泗县海岛2 875个,以分形理论讨论海岛数量与海岛面积、海岛间距的关联。结果表明,嵊泗县50%的海岛面积小于50 m~2或岛间距不足6 m,海岛数量与界定标准间呈分维数先增大后稳定的变维分形特征,分维数在220 m~2和28.5 m之后稳定在1.80和2.25。以200~500 m~2为界区分大小岛,小岛数量和海岛间距也存在变维分形特征,且分维数在间距大于50 m后趋于稳定。故嵊泗海岛最佳界定方法为以220 m~2筛选出计数海岛后再补充间距大于50 m的较小海岛,该方法下界定嵊泗海岛681个。     

Modelling the composition of melts formed during continental breakup of the Southeast Greenland margin

We have developed a generic dynamic model of extension of the lithosphere, which predicts major element composition and volume of melt generated from initial extension to steady state seafloor spreading. Stokes equations for non-Newtonian flow are solved and the mantle melts by decompression. Strengthening of the mantle due to dehydration as melting progresses is included. The composition is then empirically related to depletion. Using a crystallisation algorithm, the predicted primary melt composition was compared with mean North Atlantic mid-ocean ridge basalt (MORB). At steady state, using half spreading rates from 10 to 20 mm yr^− 1 and mantle potential temperatures of 1300 to 1325 °C we predict a major element composition that is within the variation in the mean of North Atlantic MORB.

This model is applied to the Southeast Greenland margin, which has extensive coverage of seismic and ODP core data. These data have been interpreted to indicate an initial pulse of magmatism on rifting that rapidly decayed to leave oceanic crustal thickness of 8 to 11 km. This pattern of melt production can be recreated by introducing an initial hot layer of asthenosphere beneath the continental lithosphere and by having a period of fast spreading during early opening. The hot layer was convected through the melt region giving a pulse of high magnesian and low silica melt during the early rifting process. The predicted major element composition of primary melts generated are in close agreement with primary melts from the Southeast Greenland margin. The observed variations in major element composition are reproduced without a mantle source composition anomaly.     

Structural analysis of the segmentation of the Central Indian Ridge between 20°30′S and 25°30′S (Rodriguez Triple Junction)

The morphological characteristics of the segmentation of the Central Indian Ridge (CIR) from the Indian Ocean Triple Junction (25°30S) to the Egeria Transform Fault system (20°30S) are analyzed. The compilation of Sea Beam data from R/VSonne cruises SO43 and SO52, and R/VCharcot cruises Rodriguez 1 and 2 provides an almost continuous bathymetric coverage of a 450-km-long section of the ridge axis. The bathymetric data are combined with a GLORIA side-scan sonar swath to visualize the fabric of the ridge and complement the coverage in some areas. This section of the CIR has a full spreading rate of about 50 mm yr^–1, increasing slightly from north to south. The morphology of the CIR is generally similar to that of a slow-spreading center, despite an intermediate spreading rate at these latitudes. The axis is marked by an axial valley 5–35 km wide and 500–1800 m deep, sometimes exhibiting a 100–600 m-high neovolcanic ridge. It is offset by only one 40km offset transform fault (at 22°40S), and by nine second-order discontinuities, with offsets varying from 4 to 21 km, separating segments 28 to 85 km long. The bathymetry analysis and an empirical orthogonal function analysis performed on across-axis profiles reveal morphologic variations in the axis and the second-order discontinuities. The ridge axis deepens and the relief across the axial valley increases from north to south. The discontinuities observed south of 22°S all have morphologies similar to those of the slow-spreading Mid-Atlantic Ridge. North of 22°S, two discontinuities have map geometries that have not been observed previously on slow-spreading ridges. The axial valleys overlap, and their tips curve toward the adjacent segment. The overlap distance is 2 to 4 times greater than the offset. Based on these characteristics, these discontinuities resemble overlapping spreading centers (OSCs) described on the fast-spreading EPR. The evolution of one such discontinuity appears to decapitate a nearby segment, as observed for the evolution of some OSCs on the EPR. These morphological variations of the CIR axis may be explained by an increase in the crustal thickness in the north of the study area relative to the Triple Junction area. Variations in crustal thickness could be related to a broad bathymetric anomaly centered at 19°S, 65°E, which probably reflects the effect of the nearby Réunion hotspot, or an anomaly in the composition of the mantle beneath the ridge near 19°S. Other explanations for the morphological variations include the termination of the CIR at the Rodriguez Triple Junction or the kinematic evolution of the triple junction and its resultant lengthening of the CIR. These latter effects are more likely to account for the axial morphology near the Triple Junction than for the long-wavelength morphological variation.     

南海深海生物多样性国际研究态势与热点分析

南海是西太平洋边缘海,有陆架、陆坡、岛礁、深海平原、海山、冷泉等多种生境,近10年来南海逐渐成为世界深海研究的热点。南海是中国海洋生物多样性最高的区域,与作为海洋生物多样性中心的印太珊瑚大三角区具有一定的环境与生物连通性,对南海的深海生物探测研究可丰富对西太平洋及印太交汇区生物多样性及地理分布格局的认知。目前有关南海的生物多样性研究主要集中在北部陆架浅海及岛礁,对于深海生物多样性认知明显不足。本研究梳理了全球深海生物多样性的主要国际战略布局,并对南海深海生物多样性SCIE论文发表情况进行了综合分析,探讨了南海深海生物多样性研究态势,对未来南海深海生物多样性调查与研究提出了研究展望和建议。     

宁波海岛期间带生态学研究──Ⅱ．数量组成与分布

本文研究了宁波海岛潮间带的生物数量组成与分布规律。岩礁潮间带平均生物量（２５１２．９４ｇ／ｍ２）高于沙质潮间带（４７．６４ｇ／ｍ２）高于泥沙质潮间带（２２．３６ｇ／ｍ２），而密度为岩礁潮间带（９８７．２个／ｍ２）高于泥沙质潮间带（２８１．２个／ｍ２）高于沙质潮间带（２０．０个／ｍ２）。主要生物类群有甲壳动物、藻类及软体动物。岩礁潮间带生物量从近岸向外海增加。泥沙质潮间带的生物量和密度从北至南增加。     

海底斜坡变形滑动原位观测研究

舟山群岛海域潮汐通道较多,海底斜坡失稳现象普遍发育,多发的海底滑坡对海底光缆、围海工程、港口码头等近岸设施具有很大威胁,针对其发生机制的调查研究越发受到重视。本文基于自主研发的海床变形观测系统,配合孔隙水压力观测系统和水动力观测系统,在舟山朱家尖岛西南侧典型海底斜坡自2019年8月29日开展为期75d的变形观测。结果表明：观测范围沉积物变形分为3个部分,海底斜坡底部潜在滑动面（海床下12～13.5m）沉积物累积变形量约0.75mm,侧向变形过程呈现阶梯变化特征且变形方向与斜坡倾向吻合,顶部变形与潮汐方向一致。观测发现潮位变化会改变沉积物超孔隙水压力变化,由其引发的深、浅层沉积物超孔压差改变是观测区海底斜坡潜在滑动面侧向变形的主要触发因素。     

Determining the road traffic accident hotspots using GIS-based temporal-spatial statistical analytic techniques in Hanoi,Vietnam

ABSTRACT

This study applied GIS-based statistical analytic techniques to investigate the influence of accident Severity Index (SI) on temporal-spatial patterns of accident hotspots related to the specific time intervals of day and seasons. Road Traffic Accident (RTA) data in 3 years (2015 ? 2017) in Hanoi, Vietnam were used to analyze and test this approach. Firstly, the RTA data were divided into four seasons in accordance with Hanoi’s weather conditions and the time intervals such as the daytime, nighttime, or peak hours. Then, the Kernel Density Estimation (KDE) method was applied to analyze hotspots according to the time intervals and seasons. Finally, the results were presented by using the comap technique. This study considered both analyses with and without SI. The accident SI measures the seriousness of an accident. The approach method is to give higher weights to the more serious accidents, but not with the extremely high values calculated on a direct rate to the accident expenditures. The results showed that both analyses determined the relatively similar hotspots, but the rankings of some hotspots were quite different due to the integration of SI. It is better to take into account SI in determining RTA hotspots because the gained results are more precise and the rankings of hotspots are more accurate. From there, the traffic authorities can easily understand the causes behind each accident and provide reasonable solutions to solve the most dangerous hotspots in case of limited budget and resources appropriately. This is also the first study about this issue in Vietnam, so the contribution of the article will help the traffic authorities easily solve this problem not only in Hanoi but also in other cities.     

核密度法的南京苏果超市分布热点探测

针对超市经营者进行选址优化和空间配置问题,该文以南京市主城区内苏果超市为例,利用平面核密度方法,对城市内零售超市的空间结构与分布模式进行分析,系统地研究不同类型超市的空间分布特征并进行热点区域的探测。研究表明,热点区域的探测结果符合商业网点分布的一般规律,南京主城区内不同类型苏果超市的空间分布表现出较大的空间区域分异:购物广场的热点分布于中心城区外围的次一级中心,社区店和标准超市的热点分布于居住区,便利店的热点大多分布于人口密集区域。     

一种利用HJ-IRS影像的林火火点自动检测算法

对比分析了MODIS传感器和HJ-IRS传感器的差异,在MODIS火点探测V4算法的基础上,通过对云和水体掩膜方法的改进及算法中各阈值的调整,提出了一种适于HJ-IRS的林火火点自动检测算法。以我国黑龙江地区及俄罗斯远东地区为研究对象,通过与采用V4算法生产的相同区域内同时相的MODIS火点产品进行对比分析,发现IRS火点产品在空间分布上与MODIS火点产品基本一致,并没有出现漏检现象;而在低温小火点的探测及火点的几何定位方面,HJ-IRS更具优势。     

我国西部冬季扰动源涡与东部夏季雨带分布

我国西部 (85°10 5°E)冬季“扰动源涡”的位置对夏季东部雨带的配置具有支配作用。当西部“源涡”位于 35°N以北时 ,东部雨带多出现在黄河流域及其以北 (Ⅰ类雨型 ) ;源涡位于 32°35°N之间时 ,夏季雨带多出现在淮河流域 (Ⅱ类雨型 ) ;当源涡位于 32°N以南时 ,雨带多出现在长江流域或江南 (Ⅲ类雨型 )。藏东南热点区冬季的中强地热脉冲对我国夏季江淮和川黔的大水具有很强的指示作用