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91.
92.
Gregory N. Tsokas 《Pure and Applied Geophysics》1995,144(1):117-134
The anomalies which are shown on the gravity and aeromagnetic data of the Chalkidhiki peninsula of Northern Greece reveal
the presence of three concealed dense and magnetized bodies. The ophiolitic belt which continues northwards of the geophysical
anomalies suggests that they are caused by structures which belong to it.
Multiple source Werner deconvolution shows that the lower surfaces of buried bodies in Toroneos Gulf and the one onshore are
concave upwards.
The northern concealed body has a width of 16 kilometers, while the southern one is 8 kilometres in width. A three-dimensional
model, well constrained, gives an estimate of the dimensions of the onshore feature.
The edges of the bodies, delineated by the terracing method, are formed by faults along the trend of the Hellenides orogenic
belt. The edges of the body in the outer part of Toroneos Gulf may be associated with seismic swarms that occurred in the
1980s. 相似文献
93.
Climate data from 339 meteorological stations collected from the 1950s to the early 2000s was employed to discuss aeolian activity in arid and semiarid northern China. The results show that at decadal time scales, erosivity varied greatly in this region. Most of arid and semiarid northern China was characterised by environments with moderate to low wind energy. After the 1980s, the erosivity was only 20 to 50% of that beforehand, and this difference had a significant impact on the environmental changes observed during the two periods. The dune mobility index was consistent with the observed dune activity. After the 1980s dune activity decreased and in some deserts with vegetated dune systems during the 1970s most of the dune plinths were active until the 1980s, after which only the crests were active. Some mobile dunes that had developed at the margins of mobile deserts were replaced by semi-anchored or anchored dunes. Because most desert areas with vegetated dune systems in arid and semiarid northern China are used for farming or grazing, the results of our monitoring show that the desertification trends were consistent with the trends in erosivity and dune activity in this region. Desertification was controlled much more by climatic changes than has previously been acknowledged, and especially by fluctuations in wind energy. 相似文献
94.
95.
We compared total mercury (THg) concentrations in the fur of northern fur seals (Callorhinus ursinus) from the depleted Pribilof Islands population with those of both declining and thriving populations of Steller sea lions (Eumetopias jubatus) from Prince William Sound (PWS) and Southeast Alaska (SEA), respectively. Relatively low wet weight concentrations (ranges) of THg were detected in the fur of Steller sea lion (SSL) pups (0.90-3.14 microg/g) and juveniles (0.56-6.75 microg/g) from both areas in 1998 and 2000 compared to northern fur seal (NFS) pups (3.15-8.14 microg/g) in 2000. The mean concentration +/- SD for SSLs sampled were 1.46 +/- 0.64 microg/g for pups (n = 22) and 2.74 +/- 2.89 microg/g for juveniles (n = 6). Analyses indicated higher THg concentrations from SSL pups from PWS compared to the SEA. Mean +/- SD. THg in the NFS pups was 4.90 +/- 1.42 microg/g (n = 34) and for post-partum dams was 7.84 +/- 1.78 microg/g (n = 12). 相似文献
96.
通过野外地震地质调查,在甘肃省古浪县、景泰县交界处的长岭山地区新发现了丰富的线状分布的地震地表破裂现象,表现为基岩崩塌、黄土滑坡、地震裂缝、地震土林、地震沟槽、陷落坑以及断层陡坎等,局部可见残留的破裂滑动自由面。其分布严格受长岭山北麓活动断裂控制。通过地震地表破裂带本身的特征分析、年代学分析、地表破裂带长度与震级的拟合关系以及结合区域活动断裂资料研究,认为该地震地表破裂带可能为1927年古浪8.0级地震的产物。 相似文献
97.
98.
José M. Marques Paula M. M. Carreira Luís Aires-Barros Rui C. Graça 《Environmental Geology》2000,40(1-2):53-63
At the northern part of the Portuguese mainland, the upflow zone of several hot and cold HCO3/Na/CO2-rich mineral waters is mainly associated with important NNE–SSW faults. Several geochemical studies have been carried out
on thermal and non-thermal hydromineral manifestations that occur along or near these long tectonic alignments. The slight
chemical differences that exist between these meteoric hot and cold HCO3/Na/CO2-rich mineral waters seem to be mainly caused by CO2. δ13C(TIDC) values observed in these groundwaters range between –6.00 and –1.00‰ versus V-PDB (V denotes Vienna, the site of the International
Atomic Energy Agency; PDB originates from the CaCO3 of the rostrum of a Cretaceous belemnite, Belemnitella americana, collected in the Peedee formation of South Carolina, USA) indicating a deep-seated (mantle) origin for most of the CO2. Nevertheless, in the case of the heavier δ13C(TIDC) values, the contribution of metamorphic CO2 or the dissolution of carbonate rock levels at depth cannot be excluded. Concerning the hot waters, the lack of a positive
18O-shift should be attributed to water-rock interaction in a low temperature environment, rather than to the isotopic influence
of CO2 on the δ18O-value of the waters.
Received: 9 August 1999 · Accepted: 8 March 2000 相似文献
99.
It has long been acknowledged that there are two types of El Ni(n)o events,i.e.,the eastern Pacific El Ni(n)o (EE) and the central Pacific El Ni(n)o (CE),according to the initial position of the anomalous warm water and its propagation direction.In this paper,the oceanic and atmospheric evolutions and the possible mechanisms of the two types of El Ni(n)o events were examined.It is found that all the El Ni(n)o events,CE or EE,could be attributed to the joint impacts of the eastward advection of warm water from the western Pacific warm pool (WPWP) and the local warming in the equatorial eastern Pacific.Before the occurrence of CE events,WPWP had long been in a state of being anomalous warm,so the strength of eastward advection of warm water was much stronger than that of EE,which played a major role in the formation of CE.While for the EE events,most contribution came from the local warming of the equatorial eastern Pacific.It is further identified that the immediate cause leading to the difference of the two types of El Ni(n)o events was the asynchronous variations of the Southern Oscillation (SO) and the Northern Oscillation (NO) as defined by Chen in 1984.When the transition from the positive phase of the NO (NO+) to NO- was prior to that from SO+ to SO-,there would be eastward propagation of westerly anomalies from the tropical western Pacific induced by NO and hence the growth of warm sea surface temperature anomalies in WPWP and its eastward propagation.This was followed by lagged SO-induced weakening of southeast trade winds and local warming in the equatorial eastern Pacific.These were conducive to the occurrence of the CE.On the contrary,the transition from SO+ to SO- leading the transition of NO would favor the occurrence of EE type events. 相似文献
100.
针对神狐海域的地质构造和天然气水合物的赋存特征,以重点测线三维地震数据为基础,分析讨论了基于宽带约束的模拟退火波阻抗反演方法、流程和关键技术问题,定量获得了含天然气水合物沉积物的波阻抗特征。结果表明:基于宽带约束的模拟退火波阻抗反演数据具有较高的有效垂向分辨率和较好的横向连续性;神狐海域高波阻抗异常反映了含天然气水合物沉积层,而不连续异常低波阻抗层是水合物层之下游离气的表现,这与钻探结果吻合。由此可见,基于宽带约束的模拟退火波阻抗反演可为天然气水合物层识别和预测、勘探目标圈定、钻探井位选择提供重要依据。 相似文献