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41.
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Any pair ofm L gz ,m L g b,mmxz andmm x h in the eastern six provinces of China show good linear relation this makes it easy to convert from one scale to another.mm x h may replaceM L (ECH) as the local earthquake magnitude scale for the eastern six provinces, yet retaining the level ofM L (ECH). The scalemm x h is 0.36 magnitude units higher thanM L (SC) for southern California. By comparingRm a x (Δ) withR 3 (Δ) of Yunnan, it is found that the γ-value ofMAX phase of about 1 section in Yunnan region is half as large as that in the eastern six provinces of China. Observation indicates thatmm x h≈mb for magnitude 4–5. It follows therefore thatmb (ECH)≈mb (WUS). This is supported by the result that the attenuation coefficient, the γ-value in eastern China is the same as in western United States. 相似文献
43.
多普勒雷达PPI资料在数值模式MM5中的应用 总被引:1,自引:2,他引:1
利用多普勒天气雷达观测的回波强度资料,估测大气的湿度值。假定回波强度大于4 0dBz的区域,相对湿度为1 0 0 % ,小于2 0dBz的区域相对湿度为90 % ,2 0~4 0dBz区域的相对湿度按线性变化求取。对应各点的温度值由MM5控制试验得出。然后通过迭代处理,求出对应各点的露点温度,通过以上步骤把雷达观测的回波强度值转换为模式中直接使用的物理变量,用于模式计算。为了验证该方法的可行性,进行了模拟试验,个例选用2 0 0 1年7月1 3日安徽全椒暴雨过程。背景场采用T2 1 3资料,加上常规探空,地面资料,通过分析形成控制试验的初始场。将安徽合肥新一代天气雷达观测的回波强度按上述方法加入到MM5中,形成敏感试验的初始场。水平网格为1 0 3×1 0 3,格距为1 0km ,垂直分33层,中心位置为31 0 0°N、1 1 7 6 6°E。试验结果表明,加入雷达资料后降水中心位置预报有明显改进。说明上述方法是可行的。 相似文献
44.
西藏班戈县达如错花岗斑岩LA-ICP-MS锆石U-Pb年龄、地球化学特征及其地质意义 总被引:2,自引:0,他引:2
对班公湖-怒江缝合带中段达如错地区侵入于蛇绿岩中的花岗斑岩进行了详细的野外调查及岩石学、地球化学、锆石U-Pb和Hf同位素研究。用LA-ICP-MS技术测得达如错花岗斑岩的锆石U-Pb年龄为110±1Ma,该年龄被解释为达如错花岗斑岩的形成年龄,并且锆石具有明显负的εHf(t)值(-5.5~-2.6)。全岩地球化学资料表明,达如错花岗斑岩具有高钾钙碱性系列岩浆岩的特征,且A/CNK1.1,富集Rb、Ba、Pb、Th,亏损Ta、Nb、Ti,轻稀土元素相对重稀土元素富集,同时具有明显的负Eu异常。以上特征表明,花岗斑岩属于强过铝质S型花岗岩。结合前人资料认为,达如错花岗岩岩体形成于同碰撞的构造环境,是加厚的大陆地壳发生重熔的产物,其形成还可能与同时期拉萨地块底部软流圈热物质上涌有关。班公湖-怒江缝合带中段在110Ma左右已经闭合,并发生了陆-陆碰撞。花岗斑岩侵入于蛇绿岩中,暗示110Ma之前该地区蛇绿岩就已经形成。 相似文献
45.
46.
Petrology, Geochemistry and Tectonic Significance of the Metamorphic Peridotites from Longmuco–Shuanghu Ophiolitic Melange belt, Tibet 总被引:2,自引:0,他引:2
Taoxinghu metamorphic peridotite is a firstly reported mantle sequence of ophiolite since Longmuco–Shuanghu–Lancangjiang suture zone (LSLSZ) was proposed, and it is also an important discovered for ophiolite studying in central Qiangtang. Based on detailed analyses of whole–rock geochemistry of Taoxinghu metamorphic peridotites and contrast to metamorphic peridotites in typical ophiolites worldwide, the paper investigates their petrogenesis and geological implication. The petrologic results show that the protolith of Taoxinghu metamorphic perdotites have the mineral assemblage and texture characteristic of mantle peridotite. Most metamorphic peridotites hav near global abyssal peridotites major elements contents, while the few is similar to SSZ–type peridotites. They exhibit typically U–shaped REE patterns, characterized by slight enrichment of LREE and HREE relative to MREE and a low fractionated LREE to HREE segment. Trace elements contents are low and all samples are strong enrichment in Cs, U, Pb, weak enrichment in Ba and depletion in Th, but negative Nb anomalies are only observed in few samples. That suggests Taoxinghu metamorphic peridotites have depletion mantle and suprasubduction affinities. A two–stage evolution history is considered: Taoxinghu metamorphic peridotites originated as the residue from melting at a ridge with 7%–20% degree of fraction melting and were subsequently modified by interaction with mafic melt and aqueous fluid within mantle wedge on subducted zone. Combined with previous studies, we preliminarily propose Taoxinghu metamorphic peridotites may be the Products of initial rifting of palo–Tethys, forming at middle Ordivician–upper Cambrian, and they may be the direct evidences for spreading of palo–Tethys. 相似文献
47.
天津市地震局利用天津市地震安全基础工程,对区域地磁台站的地磁观测室进行改造,拆除原有混凝土浇筑的观测墩及墩基,安装无磁大理石观测墩,拆除原屋顶新建木结构屋顶,对室内进行保温处理.在施工过程中,建筑材料及施工环节的磁性控制是磁房改造的关键环节. 相似文献
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49.
湖相滩坝砂体作为油气重要储集体类型之一,在中国东部渤海湾盆地古近系断陷湖盆中广泛发育,
其形成发育与盆地特定的演化阶段和构造-地貌背景密切相关。文章以济阳坳陷北部为例,根据盆地结构与地
貌背景将断陷湖盆滩坝分为开阔湖盆缓坡型滩坝、水下潜山台地型滩坝和潜山凸起周缘型滩坝3种成因模式。
不同构造-地貌背景下的滩坝砂体沉积特征与分布规律不同,由此导致隐蔽圈闭类型与成藏特征、成藏潜力与
有利勘探区带的差异性。开阔湖盆缓坡型滩坝规模相对较大,物性较好,主要隐蔽圈闭类型为地层超覆圈闭和
岩性圈闭,成藏潜力大;水下潜山台地型滩坝发育不整合遮挡圈闭、地层超覆圈闭和岩性圈闭;潜山凸起周缘
型滩坝可以形成陆源碎屑与碳酸盐碎屑滩坝2种成因类型,主要隐蔽圈闭类型为地层超覆圈闭和岩性圈闭,成
藏潜力相对较小。 相似文献
50.
Yafeng ZHANG Xiuxian SONG Paul J.HARRISON Sheng LIU Zhiming YU Jinjun KAN Peiyuan QIAN Hao LIU Kedong YIN 《中国科学:地球科学(英文版)》2018,(10)
High-biomass red tides occur frequently in some semi-enclosed bays of Hong Kong where ambient nutrients are not high enough to support such a high phytoplankton biomass. These high-biomass red tides release massive inorganic nutrients into local waters during their collapse. We hypothesized that the massive inorganic nutrients released from the collapse of red tides would fuel growth of other phytoplankton species. This could influence phytoplankton species composition. We tested the hypothesis using a red tide event caused by Mesodinium rubrum(M. rubrum) in a semi-enclosed bay, Port Shelter. The red tide patch had a cell density as high as 5.0×10~5 cells L~(-1), and high chlorophyll a(63.71 μg L~(-1)). Ambient inorganic nutrients(nitrate:NO_3~-, ammonium: NH_4~+, phosphate: PO_4~(3-), silicate: SiO_4~(3-)) were low both in the red tide patch and the non-red-tide patch(clear waters outside the red tide patch). Nutrient addition experiments were conducted by adding all the inorganic nutrients to water samples from the two patches followed by incubation for 9 days. The results showed that the addition of inorganic nutrients did not sustain high M. rubrum cell density, which collapsed after day 1, and did not drive M. rubrum in the non-red-tide patch sample to the same high-cell density in the red tide patch sample. This confirmed that nutrients were not the driving factor for the formation of this red tide event, or for its collapse. The death of M. rubrum after day 1 released high concentrations of NO_3~-,PO_4~(3-), SiO_4~(3-), NH_4~+, and urea. Bacterial abundance and heterotrophic activity increased, reaching the highest on day 3 or 4, and decreased as cell density of M. rubrum declined. The released nutrients stimulated growth of diatoms, such as Chaetoceros affinis var. circinalis, Thalassiothrix frauenfeldii, and Nitzschia sp., particularly with additions of SiO_4~(3-) treatments, and other species. These results demonstrated that initiation of M. rubrum red tides in the bay was not directly driven by nutrients.However, the massive inorganic nutrients released from the collapse of the red tide could induce a second bloom in low-ambient nutrient water, influencing phytoplankton species composition. 相似文献