The first peak ground motion attenuation relationships for North of Vietnam

The first attenuation relationships of peak ground acceleration (PGA) and peak ground velocity (PGV) for northern Vietnam are obtained in this study. Ground motion data are collected by a portable broadband seismic network in northern Vietnam as a part of cooperation between the Institute of Geophysics, Vietnamese Academy of Science and Technology, Vietnam and Institute of Earth Sciences, Academia Sinica, Taiwan. The database comprises a total of 330 amplitude records by 14 broadband stations from 53 shallow earthquakes, which were occurred in and around northern Vietnam in the period between 01/2006 and 12/2009. These earthquakes are of local magnitudes between 1.6 and 4.6, focal depths less than 30 km, and epicentral distances less than 500 km. The new attenuation relationships for PGA and PGV are:

log₁₀(PGA)=-0.987+0.7521M_L-log₁₀(R)-0.00475R,     

基于多源遥感数据的生态系统保育土壤价值评估——以河北省北部四地市为例

为了给合理地利用土地资源和科学地进行环境保护提供依据,利用多源遥感影像数据,结合气象数据、土壤属性数据与DEM,对河北北部地区生态系统的土壤保持量进行了评估,并参考《森林生态系统服务功能评估规范》,对生态系统保护土壤肥力的价值与固土价值进行了评估.结果表明,研究区2008年度生态系统的土壤保持总量达到7.55亿t,对应...     

Coastal defence through low crested breakwater structures: jumping out of the frying pan into the fire?

The Adriatic coast of Punta Marina (Ravenna) is protected by 3-km long low crested breakwater structures (LCSs). Through a 3-years long multidisciplinar study, we assessed the impact of such defensive structures on environmental and biological condition. LCSs create pools where conditions are very different from the surrounding nearshore system. Mechanical disturbance by currents and waves varied greatly in intensity and frequency between seaward and landward sides of the structures. Sedimentary budget was positive at the landward side, but it was due to a gain on the seafloor and not on the emerged beach. The budget at seaward was negative. LCSs determine differences in benthic assemblages, alter the seasonal pattern of communities, and modify seasonal fluctuations of animal assemblages. Landward sheltered areas can be seen as “lagoonal island” surrounded by a “sea of marine habitat”. Differences in ecological quality status, obtained through M-AMBI, are due to the sum of these factors.     

Relationships between surface-active organic substances, chlorophyll a and nutrients in the northern Adriatic Sea

Surface-active organic substances (SAS), nutrients, chlorophyll a (Chl a), dissolved oxygen (O₂), salinity (S) and temperature (T) were measured approximately monthly in the northern Adriatic Sea (NA) during two years. Results were elaborated for two stations of different trophic status. Exhaustive statistical examinations of measured variables were performed to contribute to better understanding of the processes and interdependence of the measured parameters. The results of those analyses allowed the region to be described based on several groups of data relevant for particular processes. Chl a appear to be independent parameter; orthosilicate, nitrite and ammonium represent the parameter group most relevant for regeneration processes; the second group includes nutrients dominant in freshwater inputs (orthophosphate and nitrate), while in the third group are parameters related to primary production processes (T, O₂, organic phosphorus and SAS). Probably due to time lags between nutrient uptake and phytoplankton growth as well as between cells growth/division and SAS release, both, the correlation between nutrients and Chl a and the correlation between Chl a and SAS were not statistically significant. Although significantly higher nutrient and Chl a concentrations were found in the mesotrophic western part of the region in comparison to the oligotrophic eastern part, the SAS concentration differences were less marked. It is assumed that more OM is produced, but also at the same time remineralized, at the mesotrophic western part, leading to higher concentrations of regenerated nutrients there. Presence of different phytoplankton taxa and/or fractions (micro and nano) at the two stations may have also contributed to minimize the difference in SAS contents. Higher SAS acidities were noticed in the mesotrophic than in the oligotrophic part.     

甘肃古浪长岭山北麓断裂新活动特征与地震危险性

通过野外调查和探槽开挖,并结合b值计算结果,对位于甘肃省中部古浪县的长岭山北麓断层的几何学、运动学特征、活动性分段及地震危险性进行了研究.研究认为长岭山北麓断裂主要由四条断层组成,总体呈反“S”形展布;断层最新活动在西段f1表现为倾向南的左旋正断性质,在西段f2和中段f3表现为向北倾的左旋正断性质,东段f4又转变为倾向南的左旋正断活动性质,断裂西端以秦家大山南北向隆起及第三系褶皱与古浪断裂隔断,东端以白墩子左旋拉张盆地与罐罐岭断裂左阶排列,阶距3.5 km;断裂带全新世早中期以来有过地震活动,最后一次活动离逝时间较长,现代应力积累较快,为未来地震危险区.     

青藏高原北部地区地震基本活动状态定量评价

基于区域构造背景、应力场状态及动力学环境等,将青藏高原北部地区划分为4个相对独立的统计单元,即祁连山地震带、甘东南地区、柴达木一共和地块及库玛地震带.通过地震频度和b值拟合确定了各个地区不同下限震级的地震目录完整性起始时间;确定了各构造单元中强以上地震活跃与平静交替活动的特征;定量计算了在平均状态中强以上地震活动特征参数及平静阶段与活跃阶段地震活动特征参数;分别获得了各个区域在平均、活跃与平静状态下的小震活动状态参数.     

The use of plastic debris as nesting material by a colonial seabird and associated entanglement mortality

Entanglement with plastic debris is a major cause of mortality in marine taxa, but the population-level consequences are unknown. Some seabirds collect marine debris for nesting material, which may lead to entanglement. Here we investigate the use of plastics as nesting material by northern gannets Morus bassanus and assess the associated levels of mortality. On average gannet nests contained 469.91 g (range 0-1293 g) of plastic, equating to an estimated colony total of 18.46 tonnes (range 4.47-42.34 tonnes). The majority of nesting material was synthetic rope, which appears to be used preferentially. On average 62.85 ± 26.84 (range minima 33-109) birds were entangled each year, totalling 525 individuals over eight years, the majority of which were nestlings. Although mortality rates are high, they are unlikely to have population-level effects. The use of synthetic fibres as nesting material is a common strategy among seabirds, but the impacts of entanglement warrants further investigation.     

Late Jurassic-Early Cretaceous Northern Qaidam Basin, NW China: Implications for the earliest Cretaceous intracontinental tectonism

Formation of Mesozoic western China, which was dominated by tectonic amalgamation along its southern margin and associated intracontinental tectonisms, holds a key for interpreting the succedent Cenozoic evolution. This paper presents new data including lithology, sedimentary facies, stratigraphic contact, seismic interpretation and paleo-structures within the Upper Jurassic-Lower Cretaceous strata in the northern Qaidam Basin, NW China. These data all account for a contractional tectonic deformation in the earliest Cretaceous. The South Qilian Shan, according to the sedimentary features and provenance analysis, reactivated and exhumated during the deformation, controlling the deposition of the Lower Cretaceous sequences. A simplified model for the Late Jurassic-Early Cretaceous paleogeography and tectonics of the northern Qaidam Basin is accordingly proposed. The results also support a ∼25° clockwise rotation of the Qaidam Basin since the Early Cretaceous and a more accurate Mesozoic evolution process for the basin. This earliest Cretaceous deformation, associated with the reactivation of the South Qilian Shan at the time, are part of the intracontinental tectonisms in central Asia during the Mesozoic, and probably driven by both the closure of the Mongol-Okhostk Ocean to the north and the collision of the Lhasa and the Qiangtang blocks to the south.     

碳酸盐岩成岩相研究方法及其应用——以扬子地块北缘飞仙关组鲕滩储层为例

成岩相是研究成岩作用展布的重要方法和途径,其与沉积相不同,反映岩石在一定的成岩环境下发生的各种成岩作用的综合表现。在详细的成岩作用和成岩环境研究的基础上,划分了扬子地块北缘地区飞仙关组8类成岩相、7类成岩亚相,总结了各类成岩相(亚相)的识别标志,探索了成岩相与沉积相、测井相、地震相的关系,探索了成岩相在点、线、面上的分布,预测了有利成岩相区展布,取得了良好效果。形成了一套有效的成岩相研究方法,并将成岩相研究成果应用到勘探实践,具有较好的推广价值。     

新疆东准噶尔老鸦泉富碱花岗岩型锡矿床地质及成矿流体

老鸦泉碱性花岗岩位于新疆北部东准噶尔地区。老鸦泉碱性花岗岩体及其内卡姆斯特、干梁子锡矿床的矿石和岩石的岩矿鉴定、稀土元素以及流体包裹体的系统研究表明,老鸦泉碱性花岗岩及其内的花岗斑岩及含矿石英岩、云英岩化锡矿体、石英脉锡矿体,实际上是富碱花岗质岩浆逐渐分异演化的同源和最终产物,锡成矿流体为中-高温、低盐度。碱性岩浆晚期分异的大量气水热液富锡、富硅、富碱、富含F、Cl、SO²₄离子及离子团,其氧逸度高、酸度高、温度高,这种热液引起花岗岩体的硅化、云英岩化等自变质作用,在该作用中随温度、压力的降低及CH₄等还原性气体及CO₂气体的逃逸,改变了成矿流体的氧化-还原环境,流体向相对还原及碱性条件转化,在新的氧化还原、酸碱度界面条件下,其携带的锡的络合物不稳定而分解,锡沉淀成矿。