珠江三角洲三水盆地早全新世以来 孢粉分析与古环境重建

为了深入探讨珠江三角洲的沉积古环境和古气候历史,在三水市区获取了2个高取芯率的钻孔岩芯,进行了12个AMS 14C测年,并结合孢粉、硅藻等分析结果探讨三水地区全新世的海平面与河流水动力变化,以及古植被演替过程。结果表明：钻孔所在区域全新世沉积总体从9 000 cal. a B.P.左右开始,呈现河流相―河湾相―河口湾相―潮坪相―河口湾相―河漫滩相的演变过程。三水区的早全新世沉积阶段年代最早为9 000 cal. a B.P.左右,表现为河口湾相的淤泥质粉砂沉积,硅藻以淡水种类为主,最高沉积速率为1.6 cm/a。海侵初始时间为8 700 cal. a B.P.左右,最高海平面时间为7 600 cal. a B.P.左右,此时海岸带发育红树林,丘陵山地发育较茂盛的亚常绿热带常绿阔叶林;中―晚全新世阶段（6 500―2 200 cal. a B.P.）,以泥炭粉砂沉积为主,沉积速率为0.2~0.5 cm/a,河口区高潮线附近及河流弯道低洼滩地在5 000 cal. a B.P.前后形成淡水沼泽、河口三角洲边缘区洼地水松林发育。在晚全新世（2 200 cal. a B.P.左右）以来,陆相黏土质沉积指示河口泥沙快速堆积,三角洲平原迅速扩大,沉积速率高达1.7 cm/a。孢粉结果显示次生的芒箕孢子剧增,陆地植被稀疏,人类活动显著增强。     

失水对海洋沉积物磁学性质的影响

为了探究沉积物的干燥过程及方式对其磁学性质的影响,选取含水率高的南海沉积物样品,对其中685个样品在自然条件下逐步晾干,并每间隔40 d测量1次低频磁化率（κlf）、高频磁化率（κhf）、饱和等温剩磁（SIRM）、S-300和频率磁化率系数（κfd）,共测量5次;对另外60个样品进行冷冻干燥,并在干燥前后测量相同的磁学参数。结果表明：1）自然晾干过程中,除少数异常点（约7%）外,大多数样品的κlf和κhf呈减小趋势,少数样品呈增大趋势,S-300和κfd均呈减小趋势,SIRM先减后增,整体上呈增大趋势;2）冷冻干燥过程中,样品的κlf、κhf、S-300和κfd呈增大趋势,SIRM呈减小趋势;3）2种干燥方法均不影响κlf、κhf、SIRM和S-300的剖面变化趋势,但对κfd的影响较大,这在磁学指标的古环境研究中具有关键的指示意义。磁学参数的变化,可能是由于失水过程发生的微弱氧化作用、失水导致水的抗磁性“负贡献”降低、细粒磁铁矿和磁赤铁矿在湿润状态下转变成顺磁性和不完全反铁磁性等综合因素造成的。建议对同一批次的样品采取相同的干燥方法。     

西方乡村性研究进展

在梳理20世纪60年代以来乡村性研究的社会、学术背景的基础上,聚焦于乡村性的社会建构流派及其对中国乡村转型与乡村地理研究的启示。社会建构流派将乡村性看作是社会、文化建构的过程与产物而非先存的事实,重点关注乡村转型过程中的权力关系与差异性。由描述性流派、乡土流派向社会建构流派的过渡可以看作是从关注乡村性物质层面转向想象层面,由追求乡村性的本体、核心机制向探索乡村性的认识论问题,也就是从追求“乡村性是什么”到研究“不同社会群体如何认识乡村性”“不同社会群体多样化的乡村性话语和体验”。而目前的中国乡村性研究主要关注乡村性指标及其模型建构,相关研究对于各级政府全面地了解现存的乡村问题并合理地制定乡村发展、复兴政策规划具有重要的实践意义。在西方乡村研究中,乡村性指标由于暗含线性发展观、无法解读乡村变迁的机制和过程而饱受批判。在中国乡村急剧变迁的今天,现代化乡村发展话语占据着主导地位,而在这一过程中不公平的权力关系和霸权话语对部分农村、农民的边缘化基本没有提及。在这种社会与学术背景下,乡村性社会建构流派对于解构乡村性主导话语、揭示乡村变迁过程中的权力关系及不同社会群体间利益冲突与协商具有重要意义。     

巴基斯坦北Potwar形变区地震的震源机制研究

巴基斯坦北Potwar形变区是西北喜马拉雅褶皱逆冲带前陆区的一部分，绘制了该区的地震活动性图. 与相邻地区比较，该区地震并不活跃，没有显示出与地表地质构造相关的清晰地震活动图象. 做出了4次地震的震源机制解. 结果表明，有3次地震是左旋走滑断层活动，另一次地震是逆断层活动. 地震震源机制解的P轴方向为NW-SE和NE-SW. 现今的构造形变很可能也包括基底的形变.      

跨越太平洋的合作--美日预防地震损失策略

在日本神户和美国加州北岭破坏性地震发生后,美国和日本加强了在地震政策方面的合作.1996年4月,"减轻自然灾害活动"成为两个面临全球严峻挑战的国家之间正在进行的美日全球远景规划合作计划(the United States-Japan Common Agenda for Cooperation in the Global Perspective)的一部分.     

New data on the Indus Kohistan seismic zone and its extension into the Hazara–Kashmir Syntaxis, NW Himalayas of Pakistan

This paper deals with the data obtained from local networks in northern Pakistan for 251 earthquakes of magnitude ≥4.0 for October 8, 2005 to December 31, 2006 period. The study presents focal mechanism solutions (FMS) of 12 pre- (1904–2005) and 17 post- (October 8, 2005–December, 2005) Muzaffarabad Earthquake, their detailed tectonic interpretation, and correlation with surface evidence of co-seismic rupture with published synthetic aperture radar data. Distribution of landslides obtained from National Engineering Services of Pakistan and the earthquake damages are also discussed. Aftershock distribution, which is more prominent in the crystalline zone (northwest of Muzaffarabad), defines a 50-km-wide NW–SE trending zone that extends for 200 km from the main mantle thrust to the center of the Hazara–Kashmir Syntaxis. The FMS of the main shock and 16 aftershocks having magnitude ≥4.0 indicate thrusting to be the dominant mechanism with rupture planes having NW–SE trend and NE dip. In addition, 12 FMS of pre-Muzaffarabad Earthquake (1904–2004) from the same area have been determined and results are compared. This leads to the conclusion that the wedge-shaped NW–SE trending blind zone, referred to by earlier workers as the Indus Kohistan Seismic Zone (IKSZ), has been activated during the Muzaffarabad earthquake. The right-lateral component in all FMS, supported by the surface evidences, suggests the involvement of Balakot–Bagh Fault (BBF). We propose that the IKSZ is the source of the October 8, 2005 Muzaffarabad earthquake that reactivated the BBF. Furthermore, the IKSZ does not end at the nose of the syntaxis but extends further southeast of it. Tectonic complexity seems to be due to a variety of factors. Also, thrust and reverse solutions near the northern collisional boundary (main mantle thrust) have mostly NE/SW-directed P-axis orientations. From the detailed FMS analysis, three conclusions have been drawn: (1) Shallow events (depth ≤10 km) with prominent strike slip solutions (earlier earthquakes) are associated with the surface strike slip faults (e.g., Muzaffarabad Fault) and/or the Besham domal structure; (2) moderate depth events (depth 10–25 km) with thrust/reverse solutions but having minor right-lateral strike slip component (all Muzaffarabad earthquakes and two earlier) are associated with the IKSZ; (3) deeper earthquakes (depth below IKSZ) with pure thrust/reverse solutions may be related to the under-thrusting of the Indian plate beneath the IKSZ, which represents a major thrust zone. Imbricate thrusting and breaking and thickening of the crust are considered to be caused by steep bending of the under-thrusting plate at the collisional boundary. An erratum to this article can be found at     

气象厅的强震波形观测、汇集与服务

目前,气象厅的数字强震波形观测和汇集业务是采用９５型烈度计实施的。现已在全日本以２０ｋｍ的间隔布设了约６００个采用９５型烈度计的全国性观测网（其中气象厅约１５０个,都市约１３０个,郡约１４０个,海啸地震早期检测网测点约１６０个,机动观测点约２０个）。...     

地球内磁层场向电流的统计特征

利用ISEE－1和ISEE-2飞船观测的磁场数据,分析了地球内磁层场向电流的统计特征,包括场向电流的空间（L值和地方时）分布;流进和流出电离层的场向电流随地方时的变化;场向电流发生率与地磁活动水平（以AL指数表征）、行星际磁场（IMF）Bz的关系,电流强度和密度随地磁活动水平的变化等．发现,场向电流大都发生在夜间,且集中在L为6—10区域内,场向电流发生率,强度和密度随地磁活动增强而增大,行星际磁场南向时的发生率远远高于北向时的发生率．这些结果表明,内磁层场向电流的产生是太阳风和磁层、电离层间电动耦合增加的结果．