Travel times of Pn -waves in the Aegean and surrounding area

Summary. Based on accurately located 23 very shallow earthquakes ( h = 1–14 km) in northern and central Greece by portable networks of seismic stations and by the joint epicentre method, the travel times of the P_n -waves from the foci of these earthquakes to the sites of 54 permanent stations in the Balkan region have been determined. The travel times of P_n -waves in the central and eastern part of the area (eastern Greece, south-eastern Yugoslavia, the Aegean Sea, Bulgaria, southern Romania, western Turkey) fit a straight line very well with the P_n velocity equal to 7.9 ± 0.1 km s^-1. On the contrary, the travel times of P_n -waves to stations in the western part of the area (Albania, western Greece) do not fit this curve because the P_n -waves travelling to these stations are delayed by more than 1 s due to the thicker crust under the Dinarides–Hellenides mountain range. Time delays for P_n -waves have been calculated for each permanent station in the Balkan area with respect to the mean travel-time curve of these waves in the central and eastern part of the area. Corrections of the travel times for these delays contribute very much to the improvement of the accuracy in the location of the shallow earthquakes in the Aegean and surrounding area.     

Microearthquake seismicity and fault-plane solutions in the southern Aegean and its geodynanic implications

Seismicity ( Ml <3.5) in the southern Aegean, located using data collected during seven weeks of recording by a temporary network of seismological stations, largely follows the Hellenic arc; the Sea of Crete is nearly aseismic, and only little activity is located south of the Hellenic trench, within the African plate. Focal mechanisms exhibit reverse faulting in the external part of the arc and normal faulting inside it. This normal faulting indicates N-S extension in the northern Aegean, the Gulf of Corinth, the Cyclades and Dodecanese Islands, but NW-SE extension in southern Peloponnese and western Crete and E-W extension in eastern Crete. This non-uniform strain pattern suggests that the Aegean region not only extends in a N-S sense, with the Hellenic arc moving south-westward relative to the Eurasian plate, but also by E-W extension of its southern margin, so that there is a net divergence of material.     

Active tectonics of the Alpine—Himalayan belt: the Aegean Sea and surrounding regions

Summary. New fault plane solutions, Landsat photographs, and seismic refraction records show that rapid extension is now taking place in the northern and eastern parts of the Aegean sea region. The southern part of the Aegean has also been deformed by normal faulting but is now relatively inactive. In northwestern Greece and Albania there is a band of thrusting near the western coasts adjacent to a band of normal faulting further east. The pre-Miocene geology of the islands in the Aegean closely resembles that of Greece and Turkey, yet seismic refraction shows that the crust is now only about 30 km thick beneath the southern part of the sea, compared with nearly 50 km beneath Greece and western Turkey. These observations suggest that the Aegean has been stretched by a factor of two since the Miocene. This stretching can account for the high heat flow. The sinking slab produced by subduction along the Hellenic Arc may maintain the motions, though the geometry and widespread nature of the normal faulting is not easily explained. The motions in northwestern Greece and Albania cannot be driven in the same way because no slab exists in the area. They may be maintained by blobs of cold mantle detaching from the lower half of the lithosphere, produced by a thermal instability when the lithosphere is thickened by thrusting. Hence generation and destruction of the lower part of the lithosphere may occur beneath deforming continental crust without the production of any oceanic crust.     

南极普里兹湾附近海域表层海流特征分析

利用第29次南极科考期间在普里兹湾海区释放的8个Argos漂流浮标所获的总计662 d的数据,对普里兹湾及其邻近海域的表层海流特征进行了分析,并和以前的研究结果进行对比,结果表明:普里兹湾西部和北部表层海流基本呈现向西的流动,说明此地区的表层海流以沿南极大陆的逆时针沿岸流为主。普里兹湾东部海流呈现先向南再向西或先向南再向北的流动,普里兹湾西北部海流呈现向南的流动。8个浮标平均流速在0.02—0.20 m·s~(-1)之间,最大流速为1.57 m·s~(-1),流速1.0 m·s~(-1)的大流速区主要集中在普里兹湾、克洛斯角外侧、达恩利角外侧海域,流速1.5 m·s~(-1)的大流速区只出现在普里兹湾、克洛斯角外侧两处海域。     

中国亚热带地区柑桔气候风险变化(英文)

Based on the citrus temperature, precipitation, sunlight and climate risk degree, the article divides subtropics of China into three types: the low risk region, the moderate risk region and the high risk region. The citrus temperature risk increases with increasing latitude (except for the western mountainous area of subtropics of China). The citrus precipitation risk in the central part of subtropics of China is higher than that in the northern and western parts. The distributions of citrus sunlight risk are not consistent to those of the citrus precipitation risk. The citrus climate risk is mainly influenced by temperature. There is latitudinal zonal law for the distribution of the climate risk, that is, the climate risk increases with increasing latitude. At the same time the climate risk in mountainous area is high and that in eastern plain area is low. There are differences in the temporal and spatial changes of the citrus climate. In recent 46 years, the citrus climate risk presents a gradual increasing trend in subtropics of China, especially it has been increasing fast since the 1980s. Because of the global warming, the low risk region in the eastern and southern parts has a gradual decreasing trend, however, the high risk region in the northern and western parts has an increasing trend and the high risk region has been extending eastward and southward. The article analyses the distribution of the citrus climate risk degree of reduction rates of >10%, >20% and >30% in subtropics of China, and studies their changes in different time periods. Results show that the risk is increasing from southeast to northwest.     

Changes of citrus climate risk in subtropics of China

Based on the citrus temperature, precipitation, sunlight and climate risk degree, the article divides subtropics of China into three types: the low risk region, the moderate risk region and the high risk region. The citrus temperature risk increases with increasing latitude (except for the western mountainous area of subtropics of China). The citrus precipitation risk in the central part of subtropics of China is higher than that in the northern and western parts. The distributions of citrus sunlight risk are not consistent to those of the citrus precipitation risk. The citrus climate risk is mainly influenced by temperature. There is latitudinal zonal law for the distribution of the climate risk, that is, the climate risk increases with increasing latitude. At the same time the climate risk in mountainous area is high and that in eastern plain area is low. There are differences in the temporal and spatial changes of the citrus climate. In recent 46 years, the citrus climate risk presents a gradual increasing trend in subtropics of China, especially it has been increasing fast since the 1980s. Because of the global warming, the low risk region in the eastern and southern parts has a gradual decreasing trend, however, the high risk region in the northern and western parts has an increasing trend and the high risk region has been extending eastward and southward. The article analyses the distribution of the citrus climate risk degree of reduction rates of >10%, >20% and >30% in subtropics of China, and studies their changes in different time periods. Results show that the risk is increasing from southeast to northwest.     

青藏高原积雪分布与变化特征

本文对青藏高原ＳＭＭＲ修积雪深度、ＮＯＡＡ周积雪面积、地面台站积雪深度进行了分析。结果表明青藏高原东西两侧多雪与腹地少雪形成鲜明对比,高原东部是高原积雪年际变化最显著的地区,它主导了整个高原积雪的年际变化,并且与西部多雪区年际波动呈反位相关系。从６０年代到８０年代积雪年际波动幅度有明显增加趋势,积雪变化具有３年左右准周期。随着全球变暖,青藏高原积雪将会有所增加。     

基于K-means聚类分区的西北地区近半个世纪气温变化特征分析

采用K-means聚类分区,Sen’s斜率估计,Kendall-Tau非参数检验等方法,分析和讨论了近半个世纪（1960—2015年）我国西北地区不同区域的气温变化特征。发现近半个世纪西北地区气温保持了持续的显著上升,年均最低气温上升速率高于年均气温和年均最高气温。从空间的角度来看,新疆北疆地区的东北部,内蒙古北部、西部中东部,甘肃中部、西部,青海北部、中部,宁夏中部、北部地区以及陕西北部是升温最快的区域。虽然西北地区气温总体是上升趋势,但在时间上并不均匀一致。从1998年开始,西北地区气温升温减缓,部分地区出现了下降趋势。近半个世纪西北地区季节气温与年际气温变化趋势并不一致,变暖减缓在该地区不同季节的响应不同。1998—2015年,冬季是增温幅度最小的季节,多数子区冬季存在升温趋势减缓,甚至转为下降趋势。     

中国城市分布特征及其影响因素

通过对221 BC-1911 AD年间中国城市分布特征及其影响因素的研究,发现：① 在整个研究阶段,中国城市分布的重心位于中东部地区,秦—唐时期重心向西南地区大幅移动,唐—元时期重心先东北方向移动后转向西南方向,元—清时期重心主要向北移动。以腾冲—瑷珲一线为界线分区研究发现,在整个研究阶段西部重心在南北及东西方向呈现出较大的波动趋势,东部重心呈现出与全国类似的运动轨迹。② 标准差椭圆分析表明全国及东西部地区城市分布经历了明显的分散—集聚—分散的变化趋势,其中西部地区最为明显。从城市分布的平均方向看,全国及东部地区具有一定的相似性,均以东北—西南为主要分布特征,西部地区是以西北—东南为主要分布特征。③ 从城市密度分布特征看,其空间连续性和自组织性不断加强且由空间相关性引起的结构性变异处于显著状态。从方向上来看,全方向上的均质化程度呈下降趋势,西北—东南方向各时期城市密度均质化程度相对较好,空间差异相对较小,而东—西方向差异最为明显。④ 分析不同时期城市设置的相关因素发现,221 BC-1911 AD年间,中国城市设置相对集中在地形平坦、气候适中且靠近河流及中心城市的地区。     

中国季风温冰川区近代气候变化与冰川动态

通过对中国季风温冰川区的气候实测资料、冰芯记录、树木年轮指数和冰川进退记载等多种指标的综合分析,较详细地研究了400年以来本区气候与冰川变化。自17~19世纪小冰期的两个寒冷阶段以后,中国季风温冰川分布区气温普遍波动上升,与全球变暖的大背景一致, 大部分冰川正在后退,但降水量变化则比较复杂,达索普冰芯记录证明,本区西部的喜马拉雅山地区降水量表现为下降的趋势,与气温变化相反,而东部的横断山等地的降水则表现为上升的趋势,与气温变化同步,这主要是不同来源大气环流影响的结果。研究区主要盛行来源于印度洋的西南季风,此外,其东部还受来源于西太平洋东南季风的影响,西部受西风环流南支的影响,造成中国季风温冰川区东西部不均匀的降水分布和变化趋势。小冰期以后,我国的季风温冰川对气候变暖反应敏感,绝大部分冰川持续后退。20世纪80年代以来,后退速度加剧, 但后退幅度和规模因地而异。     

中国化石能源补贴区域分布及改革影响效应研究

从区域分布视角出发,采用价差法估算了中国2006~2015年化石能源补贴量。结果表明：能源补贴呈现东、中、西部地区依次递减的格局,分别为2.72万亿元、1.80万亿元和1.53万亿元;能源补贴存在较强的空间相关性,且呈现显著的“俱乐部”现象;取消能源补贴对于中国实现“十一五”期间节能减排目标具有重要意义,具体来说,可使全国能源强度下降幅度由19.10%提升为22.36%;取消能源补贴的东部地区节能减排效应最为明显,中部地区敏感程度相对较弱;同时,取消能源补贴会导致居民生活成本不同幅度上涨,其中中部地区居民面临最大的影响,尤其是农村居民受到的冲击更为显著;化石能源补贴改革进程中,政府需要加大对中部地区尤其是农村居民扶持力度,以抵消可能进一步拉大贫富差距的风险。     

一种新的气候变化敏感区的定义方法与预估

气候变化敏感区的研究是气候变化研究的一个重要方向,前人对气候变化敏感区的定义大多基于单一的指标,而对综合性指标研究较少。基于柯本气候分类法所划分出的中国气候类型分布及其变化频次,提出一种新的气候变化敏感区定义方法,并使用该方法划分中国的气候变化敏感区,气候类型变化频繁的区域被认为是敏感区。选取CESM模型中等碳排放（RCP 4.5）下的模拟数据计算2006-2013年、21世纪40年代和90年代气候类型的变化,以此预估未来30~80年间气候变化敏感带的变化。结果显示：依据本文提出的方法划分的气候变化敏感区,与降水变化敏感区有较好拟合;中国气候变化最敏感的区域分布在黑河腾冲线附近、秦岭淮河一线、青藏高原西部和天山以北部分地区,气候最为稳定的区域分布在青藏高原中东部、昆仑山、祁连山以北、天山以南、贺兰山以西的大片区域和大兴安岭附近;未来30~80年间,西部（贺兰山、横断山以西）地区气候变化敏感区基本不变,而东部地区的气候变化敏感区则逐渐向北偏移。     

New insight into the crust and upper mantle structure under Alaska

To better understand the seismic structure of the subducting Pacific plate under Alaska, we determined the three-dimensional P-wave velocity structure to a depth of approximately 200 km beneath Alaska using 438,146 P-wave arrival times from 10,900 earthquakes. In this study an irregular grid parameterization was adopted to express the velocity structure under Alaska. The number of grid nodes increases from north to south in the study area so that the spacing between grid nodes is approximately the same in the longitude direction. Our results suggest that the subducting Pacific slab under Alaska can be divided into three different parts based on its geometry and velocity structure. The western part has features similar to those in other subduction zones. In the central part a thick low-velocity zone is imaged at the top of the subducting Pacific slab beneath north of the Kenai Peninsula, which is believed to be most likely the oceanic crust plus an overlying serpentinized zone and the coupled Yakutat terrane subducted with the Pacific slab. In the eastern part, significant high-velocity anomalies are visible to 60–90 km depth, suggesting that the Pacific slab has only subducted down to that depth.     

喜马拉雅中部甘达基河流域尼泊尔国鸟(棕尾虹雉)生境分布变化

甘达基河流域(Gandaki River Basin,GRB)是喜马拉雅中部地区的一部分,该地区栖息着许多珍稀的野生动物。由于气候和人类活动的影响,许多珍稀保护物种的生境处于危险之中。本研究基于最大熵(MaxEnt)模型,运用生物气候、土地覆被和DEM数据,分析各环境要素对棕尾虹雉(Lophophorusimpejanus)的生境适宜性的影响,评估棕尾虹雉现在状况和未来栖息地分布的变化。研究表明,目前棕尾虹雉的高度适宜栖息地面积约为749 km^2,主要分布在流域北部、东部和西部,尤其是郎塘国家公园、马纳斯卢峰自然保护区和安纳布尔纳峰自然保护区等保护区内。到2050年,棕尾虹雉的高度适宜栖息地面积将减少至561 km^2,主要在流域北部和西北部(即Chhyo,Tatopani,Humde和Chame地区)。未来环境变化的模拟表明,由于适宜栖息地面积的减少,棕尾虹雉面临的生存风险将增加。     

Distribution Characteristics of In Situ Stress Field and Vertical Development Unit Division of CBM in Western Guizhou,China

In situ stress is not only a vital indicator for selecting explorative regions of coalbed methane (CBM), but also a pivotal factor affecting CBM production. The present study explored whether in situ stress affected the development potential of CBM in western Guizhou, China. To this end, we collected injection/falloff well test data and gas content data from 70 coal seams in 28 wells. The study found that from top to bottom, strike slip fault stress fields (<?500 m), normal fault stress fields (500–1000 m) and strike slip fault stress fields (>?1000 m) were successively developed in western Guizhou. The distribution features of vertical permeability in western Guizhou are consistent with the stress fields' transformation location. The coal permeability in the western part in Guizhou presents a tendency of increase followed by decrease as a result of increased burial depth. The vertical development characteristics of coal seam gas content are controlled mainly by reservoir pressure, and the relationship between reservoir pressure and buried depth shows a linear increase. The CBM in western Guizhou is divided vertically into three development potential regions dependent on the characteristics of burial depth, permeability and gas content of coal seams. The most favorable vertical development potential region in western Guizhou is 500–1000 m. This region exhibits high gas content, high permeability and moderate burial depth, which are favorable for the production of CBM. These research results can provide basis for geological selection and engineering implementation of CBM in western Guizhou.

     

中国纺织服装产业的区位迁移

纺织服装业因其自身产业特点和发展特征, 一直是国内研究的热点, 被认为是最早实现全球产业转移和最具有产业转移特征的重要产业之一。通过构建产业结构变动系数来描绘纺织服装业区位迁移的基本格局, 结果表明:① 纺织服装产业的结构变动相对稳定且集中于东部地区;② 结构变化地域分异明显, 沿海大于内陆, 东部大于中部, 中部又高于西部和东北, 东部沿海的浙江、广东、江苏、山东、上海和福建, 中部的湖北和河南, 以及东北的辽宁, 纺织服装业的结构变化系数均高于全国平均水平, 西部地区的多数省份则较低;③ 结构变动系数的大小取决于当地经济发展、区位性和结构性因素。采用偏离-份额模型将中国纺织服装业发展分解为结构效应和空间效应, 以此阐述中国纺织服装业区位迁移的内在规律。结果表明:① 河南、安徽和江西已经成为东部纺织服装业转移的主要承接地区;② 纺织服装业的区位迁移在竞争效应和纯空间竞争效应上具有一致性, 说明产业的地理分布主要受到区位优势的影响;③ 明显的结构负效应说明纺织服装业的产业结构有待于进一步优化。     

中国农业产业化龙头企业空间分布特征——以国家级重点龙头企业为例

根据880家国家级农业产业化重点龙头企业地理位置、主营业务等资料,利用相关分析、生态分布格局理论等方法,分析了龙头企业在宏观、微观地域及分行业空间布局特征。结果表明：①龙头企业以东部地区聚集为主,西部地区比重有一定提高,东部地区比重有波动;农业发展规模、经济发展水平较高省份聚集企业多,一省农产品丰富度与其龙头企业数相关性亦很显著;②龙头企业在各省内分布聚集程度不一,总体都以聚集为主,尤其以省会城市或中心城市聚集居多。但河北、浙江省内呈均匀分布;③在县级区域,存在一些龙头企业聚集县、专业化县,东部地区聚集县多,中部地区专业化程度高,西部地区特色产业聚集;④划定的17类龙头企业行业,聚集程度大体可分为四类,但总体上对原料依赖行业聚集程度高,对市场依赖行业聚集程度低。     

青藏高原植被覆盖变化与降水关系

The temporal and spatial changes of NDVI on the Tibetan Plateau, as well as the relationship between NDVI and precipitation, were discussed in this paper, by using 8-km resolution multi-temporal NOAA AVHRR-NDVI data from 1982 to 1999. Monthly maximum NDVI and monthly rainfall were used to analyze the seasonal changes, and annual maximum NDVI, annual effective precipitation and growing season precipitation (from April to August) were used to discuss the interannual changes. The dynamic change of NDVI and the corre- lation coefficients between NDVI and rainfall were computed for each pixel. The results are as follows: (1) The NDVI reached the peak in growing season (from July to September) on the Tibetan Plateau. In the northern and western parts of the plateau, the growing season was very short (about two or three months); but in the southern, vegetation grew almost all the year round. The correlation of monthly maximum NDVI and monthly rainfall varied in different areas. It was weak in the western, northern and southern parts, but strong in the central and eastern parts. (2) The spatial distribution of NDVI interannual dynamic change was different too. The increase areas were mainly distributed in southern Tibet montane shrub-steppe zone, western part of western Sichuan-eastern Tibet montane coniferous forest zone, western part of northern slopes of Kunlun montane desert zone and southeastern part of southern slopes of Himalaya montane evergreen broad-leaved forest zone; the decrease areas were mainly distributed in the Qaidam montane desert zone, the western and northern parts of eastern Qinghai-Qilian montane steppe zone, southern Qinghai high cold meadow steppe zone and Ngari montane desert-steppe and desert zone. The spatial distribution of correlation coeffi- cient between annual effective rainfall and annual maximum NDVI was similar to the growing season rainfall and annual maximum NDVI, and there was good relationship between NDVI and rainfall in the meadow and grassland with medium vegetation cover, and the effect of rainfall on vegetation was small in the forest and desert area.     

The relationship between NDVI and precipitation on the Tibetan Plateau

The temporal and spatial changes of NDVI on the Tibetan Plateau, as well as the relationship between NDVI and precipitation, were discussed in this paper, by using 8-km resolution multi-temporal NOAA AVHRR-NDVI data from 1982 to 1999. Monthly maximum NDVI and monthly rainfall were used to analyze the seasonal changes, and annual maximum NDVI, annual effective precipitation and growing season precipitation (from April to August) were used to discuss the interannual changes. The dynamic change of NDVI and the corre-lation coefficients between NDVI and rainfall were computed for each pixel. The results are as follows: (1) The NDVI reached the peak in growing season (from July to September) on the Tibetan Plateau. In the northern and western parts of the plateau, the growing season was very short (about two or three months); but in the southern, vegetation grew almost all the year round. The correlation of monthly maximum NDVI and monthly rainfall varied in different areas. It was weak in the western, northern and southern parts, but strong in the central and eastern parts. (2) The spatial distribution of NDVI interannual dynamic change was different too. The increase areas were mainly distributed in southern Tibet montane shrub-steppe zone, western part of western Sichuan-eastern Tibet montane coniferous forest zone, western part of northern slopes of Kunlun montane desert zone and southeastern part of southern slopes of Himalaya montane evergreen broad-leaved forest zone; the decrease areas were mainly distributed in the Qaidam montane desert zone, the western and northern parts of eastern Qinghai-Qilian montane steppe zone, southern Qinghai high cold meadow steppe zone and Ngari montane desert-steppe and desert zone. The spatial distribution of correlation coeffi-cient between annual effective rainfall and annual maximum NDVI was similar to the growing season rainfall and annual maximum NDVI, and there was good relationship between NDVI and rainfall in the meadow and grassland with medium vegetation cover, and the effect of rainfall on vegetation was small in the forest and desert area.     

Teleseismic delay-time tomography of the upper mantle beneath southeastern India: imprint of Indo–Antarctica rifting

A 3-D P -velocity map of the crust and upper mantle beneath the southeastern part of India has been reconstructed through the inversion of teleseismic traveltimes. Salient geological features in the study region include the Archean Dharwar Craton and Eastern Ghat metamorphic belt (EGMB), and the Proterozoic Cuddapah and Godavari basins. The Krishna–Godavari basin, on the eastern coastal margin, evolved in response to the Indo–Antarctica breakup. A 24-station temporary network provided 1161 traveltimes, which were used to model 3-D P -velocity variation. The velocity model accounts of 80 per cent of the observed data variance. The velocity picture to a depth of 120 km shows two patterns: a high velocity beneath the interior domain (Dharwar craton and Cuddapah basin), and a lower velocity beneath the eastern margin region (EGMB and coastal basin). Across the array velocity variations of 7–10 per cent in the crust (0–40 km) and 3–5 per cent in the uppermost mantle (40–120 km) are observed. At deeper levels (120–210 km) the upper-mantle velocity differences are insignificant among different geological units. The presence of such a low velocity along the eastern margin suggests significantly thin lithosphere (<100 km) beneath it compared to a thick lithosphere (>200 km) beneath the eastern Dharwar craton. Such lithospheric thinning could be a consequence of Indo–Antarctica break-up.