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91.
为了进一步研究唐山地区深部地壳构造与唐山大地震孕育及发生的关系,国家地震局地球物理研究所在石油部物探局的协助下,于1985年1月在唐山震区完成了64km长的深反射剖面野外观测,获得了高分辨率的整个地壳结构的详细资料。分析结果表明,唐山震区内深度500m以上的沉积层十分破碎;结晶基底为前震旦纪地层,埋深2-7km不等,覆盖地层倾斜,且断层发育,其中陡河断裂为正断层,延深至6-7km,推断该断层为1976年唐山发震的重要构造之一。测线上大约21km深处普遍存在一反射层;莫霍面深度在31-32km左右,与该地区折射剖面得到的结果相当一致。 相似文献
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具有重要岩石学和构造学意义的科马提岩,最吸引人同时又最令人困惑的特征之一是它的鬣刺结构和分层构造。本文从喷出地表的岩桨冷凝时温度分布、熔体性质与结晶作用的密切联系,把科马提岩浆喷发形成的岩流作为一个冷凝整体。通过与金属铸锭浇注成形和矿石冶炼生产的比较,发现它们在冷凝固结过程中温度场特征、熔体的性质、结晶能力和结晶方式都有十分相似的特点,并以此为出发点详细解析了科马提岩的鬣刺结构和岩石分层构造的形成 相似文献
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福州盆地及其周围地区地壳深部结构与构造的初步研究 总被引:20,自引:4,他引:20
1986-1988年,福建省地震局在福州盆地及其周围地区完成了五条地震测深剖面:宁德-永春剖面;洪懒-宁德剖面;莲峰-福州(尚干)剖面;南平-永泰-平潭非纵剖面;并在宁德-古田-嵩口首次试验扇形剖面观测系统,结果表明,扇形剖面对确定断裂是有效的. 根据对地震波走时的正、反演计算,用理论地震图和射线追踪方法进一步修改和完善,得到了福州盆地及其周围地区地壳深部为高、低速相间的速度分布特征.地壳介质速度为6.40km/s,在中地壳普遍发育一层速度为5.80-5.90 km/s、厚度约5.0 km的低速层.Moho面深度30-33 km,福州盆地为一Moho面隆起区,隆起幅度达3.0 km.北西向断裂发育,其中,闽江断裂在纵剖面和扇形剖面均有明显的反映,并切割到Moho面2.0-3.0 km. 反射波谱频方法计算得到福州盆地地壳Q值仅120-150,比邻近地区明显偏低,中地壳低速层Q值为40-80,是一典型的低速-高导-低Q(高衰减)结构层,此层上界面埋深14-15 km,与居里面埋深较一致.这些结果为福州地区的地热资源远景预测和开发提供了地壳深部结构和某些地球物理场背景. 相似文献
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Rock salt is approximately 1000 times more soluble than limestone and thus displays high rates of geomorphic evolution. Cave stream channel profiles and downcutting rates were studied in the Mount Sedom salt diapir, Dead Sea rift valley, Israel. Although the area is very arid (mean annual rainfall ≈ 50 mm), the diapir contains extensive karst systems of Holocene age. In the standard cave profile a vertical shaft at the upstream end diverts water from a surface channel in anhydrite or clastic cap rocks into the subsurface route in the salt. Mass balance calculations in a sample cave passage yielded downcutting rates of 0–2 mm s?1 during peak flood conditions, or about eight orders of magnitude higher than reported rates in any limestone cave streams. However, in the arid climate of Mount Sedom floods have a low recurrence interval with the consequence that long-term mean downcutting rates are lower: an average rate of 8·8 mm a?1 was measured for the period 1986–1991 in the same sample passage. Quite independently, long-term mean rates of 6·2mm a?1 are deduced from 14C ages of driftwood found in upper levels of 12 cave passages. These are at least three orders of magnitude higher than rates established for limestone caves. Salt cave passages develop in two main stages: (1) an early stage characterized by high downcutting rates into the rock salt bed, and steep passage gradients; (2) a mature stage characterized by lower downcutting rates, with establishment of a subhorizontal stream bed armoured with alluvial detritus. In this mature stage downcutting rates are controlled by the uplift rate of the Mount Sedom diapir and changes of the level of the Dead Sea. Passages may also aggrade. These fast-developing salt stream channels may serve as full-scale models for slower developing systems such as limestone canyons. 相似文献
99.
From July to September of 1990,CH_4 flux measurements were made in Lin'an rice paddies using gradient profiletechniques.Some characteristics of the turbulence structure under the stable conditions have been verified in the surfacelayer according to the in situ measurements.The semi-empirical turbulent parameters β_m,β_h and β_c and their changeswith the stability parameter Ri are given.Observed results indicate that CH_4 flux in the rice-paddy is mainly decided bythe methnogenesis and the process of CH4 transport from internal soils to the atmosphere,and that the CH_4 verticaltransfer is depressed in the stable surface layer.The CH_4 flux shows that its obvious diurnal changes,and the meanCH_4 flux are higher in nighttime and lower in daytime,and the peaks appear at about 2000 BST at night and 0300 BSTin the early morning,respectively.The mean value of CH_4 flux is about 4.18±2.3 mg/m~2 h. 相似文献
100.
From July to September of 1990,CH4 flux measurements were made in Lin'an rice paddies using gradient profile techniques.Some characteristics of the turbulence structure under the stable conditions have been verified in the surface layer according to the in situ measurements.The semi-empirical turbulent parameters βm,βh and βc and their changes with the stability parameter Ri are given.Observed results indicate that CH4 flux in the rice-paddy is mainly decided by the methnogenesis and the process of CH4 transport from internal soils to the atmosphere,and that the CH4 vertical transfer is depressed in the stable surface layer.The CH4 flux shows that its obvious diurnal changes,and the mean CH4 flux are higher in nighttime and lower in daytime,and the peaks appear at about 2000 BST at night and 0300 BST in the early morning,respectively.The mean value of CH4 flux is about 4.18±2.3 mg/m2 h. 相似文献