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Marcelo Assumpo Meijian An Marcelo Bianchi George S.L. Frana Marcelo Rocha Jos Roberto Barbosa Jesús Berrocal 《Tectonophysics》2004,388(1-4):173
The Tocantins Province in Central Brazil is composed of a series of SSW–NNE trending terranes of mainly Proterozoic ages, which stabilized in the Neoproterozoic in the final collision between the Amazon and São Francisco cratons. No previous information on crustal seismic properties was available for this region. Several broadband stations were used to study the regional patterns of crustal and upper mantle structure, extending the results of a recent E–W seismic refraction profile. Receiver functions and surface wave dispersion showed a thin crust (33–37 km) in the Neoproterozoic Magmatic Arc terrane. High average crustal Vp/Vs ratios (1.74–1.76) were consistently observed in this unit. The foreland domain of the Brasília foldbelt, on the other hand, is characterized by thicker crust (42–43 km). Low Vp/Vs ratios (1.70–1.72) were observed in the low-grade foreland fold and thrust zone of the Brasília belt adjacent to the São Francisco craton. Teleseismic P-wave tomography shows that the lithospheric upper mantle has lower velocities beneath the Magmatic Arc and Goiás Massif compared with the foreland zone of the belt and São Francisco craton. The variations in crustal thickness and upper mantle velocities observed with the broadband stations correlate well with the measurements along the seismic refraction profile. The integration of all seismic observations and gravity data indicates a strong lithospheric contrast between the Goiás Massif and the foreland domain of the Brasília belt, whereas little variation was found across the foldbelt/craton surface boundary. These results support the hypothesis that the Brasília foreland domain and the São Francisco craton were part of a larger São Francisco-Congo continental plate in the final collision with the Amazon plate. 相似文献
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为使已获得的中国大陆中上地壳结构更为可靠,本文搜集了很多对浅部结构分辨率较好的短周期面波资料. 与传统面波层析成像反演方法不同,本文在第二步由面波频散得到剪切波速的过程中不再对每个结点进行一维波速模型分别反演,而是直接将所有结点上的区域化频散转换成三维波速结构的线性化约束,实现了直接的三维反演. 检测板测试结果显示该方法可以得到理想的反演结果. 本文得到的波速模型显示,中国大陆中上地壳的速度分布存在明显的横向变化和分区特征. 较低的波速异常很好地勾勒出我国主要的沉积盆地,波速异常在不同深度上的变化在一定程度上反映了各盆地结晶基底的深度. 以东经95deg;为界,特提斯构造域西部具有明显的低速异常,而东部基本没有低速异常. 基于油气资源多存在于沉积层中,而沉积层表现低速异常,我们推测特提斯构造域西部油气前景比东部好. 另外, 由于特提斯构造域西部低速非常明显,这可能也说明了其地壳温度较高. 兴安造山带的低速异常可能也说明了其地壳温度较高. 20 km深度上鄂尔多斯盆地西侧的弱低速带, 很好地勾勒出中国大陆近似沿105deg;经线的强震带的走势. 相似文献
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Meijian Zhang Yurong Ma Xinyi Che Zumei Huang Peng Chen Guanghua Xia Meihui Zhao 《中国海洋大学学报(英文版)》2020,19(2):439-445
This study investigated the difference of nutrient composition in Caulerpa lentillifera collected from different regions.The nutrient compositions of C.lentillifera from China's Hainan and Shandong provinces were determined and compared with those from Semporna(Malaysia),Sabah(Malaysia),Petchburi(Thailand),and two other species of seaweeds(Malaysia).The results showed that the polysaccharide and protein contents of C.lentillifera from Hainan(44.82%±0.98%and 12.5%±0.70%),Shandong(43.22%±1.42%and 14.7%±0.72%),Petchburi(59.27%±2.31%and 12.49%±0.30%),and Sabah(44.02%±2.01%and 19.38%±1.48%)were higher than those of Eucheuma cottonii(26.49%±3.01%and 9.76%±1.33%)and Sargassum polycystum(33.49%±1.70%and 5.40%±0.07%),respectively.The polyunsaturated fatty acid contents in C.lentillifera from Hainan(29.98%)and Shandong(22.11%)were higher than that in Semporna(16.76%±0.27%),Sabah(9.49%),and S.polycystum(20.34%±0.43%),but lower than that in E.cottonii(51.55%±0.57%).In Caulerpa lentillifera of Hainan and Shandong provinces,the essential amino acid(EAA)/total amino acid(TAA)ratios were 35.22%and 38.78%,respectively;and the EAA/ETAA ratios were 54.36%and 63.35%,respectively.The EAA composition of C.lentillifera was close to the ideal model of Food and Agriculture Organization/World Health Organization.C.lentillifera was rich in mineral elements,including calcium((3315.85±127.55)mg(100 g)^-1 and(3728.35±92.38)mg(100 g)^-1),magnesium((6715.74±82.58)mg(100 g)^-1 and(8128.59±242.72)mg(100 g)^-1),and trace elements,including iron((510.65±5.47)mg(100 g)^-1 and(1972.97±183.35)mg(100 g)^-1),selenium((1.04±0.08)mg(100 g)^-1 and(0.83±0.15)mg(100 g)^-1),and zinc((33.90±0.13)mg(100 g)^-1 and(11.75±2.05)mg(100 g)^-1).These results showed that C.lentillifera was more nutritious than S.polycystum or E.cottonii in terms of polysaccharide,protein,and fatty acid contents.Furthermore,both C.lentillifera species collected from Hainan and Shandong provinces show more basic nutrients.Therefore,C.lentillifera has important development and application prospects. 相似文献
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针对气枪主动源监测中相位加权叠加数据绝对到时拾取可能存在较大误差的问题,提出基于台站之间叠加信号波形的相似性,利用台站对波形的互相关得到更准确到时差的策略。在此基础上,将台站对双差地震速度成像方法直接用于台站对到时差数据,以确定地下介质的速度异常。本文利用长江安徽段气枪实验在庐江临时地震台阵接收到的数据进行了测试,发现基于波形互相关得到的到时差数据比绝对到时数据更准确。最后,采用台站对双差地震成像的方法,得到了庐江台阵覆盖区域的地壳三维速度异常模型,继而确定了该地区较大尺度的地下结构分布。 相似文献
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动态遗传算法及其在P波初动震源机制解中的应用 总被引：9，自引：0，他引：9
利用动态遗传算法对Ｐ波初动震源机制解进行反演计算，并与前人常用的反演计算方法对比，认为遗传算法在Ｐ波初动 震源机制解中的应用是有很有效的。 相似文献
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在野外进行地震监测是地震学的基础工作.地震监测设备的设计工作温度一般在-20℃以上,但高纬高寒地区冬季环境温度往往低于此温度.参照国外经验,基于我们在南极内陆和我国长白山低温地震监测的工作经历,对如何做好低温条件下的天然地震监测进行介绍.实践证明,对地震记录仪和电池等实施被动保温非常必要,持续供电能力则是连续地震监测工作成败的关键. 相似文献
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现今塔里木克拉通岩石圈厚度分析及机制探讨 总被引：2，自引：0，他引：2
塔里木盆地是青藏高原周边稳定的克拉通陆块,在印度板块与欧亚板块碰撞过程中一直保持稳定,盆地内部没有发生强烈的变形,其地壳热状态也同样保持稳定,地温梯度没有明显的变化,以热力学为基础的岩石圈热学厚度约为250km左右,该厚度是热稳态岩石圈的厚度。而最新的地震热学方法的研究成果表明塔里木盆地的岩石圈厚度仅为150km左右,这表明塔里木盆地岩石圈的热结构可能并不是处于稳态状态,其底部正在或已经发生了减薄。本文利用构造热演化方法对塔里木岩石圈减薄的热演化过程进行了定量分析,探讨了塔里木盆地岩石圈减薄可能的三种机制：印度板块与欧亚板块碰撞后青藏高原岩石圈底部的软流圈较塔里木盆地岩石圈底部的软流圈的温度要高,青藏高原的软流圈地幔向塔里木盆地岩石圈底部侵入形成的热扰动使得塔里木盆地岩石圈底部的温度升高;塔里木岩石圈与其下流动的软流圈的摩擦剪切生热导致其岩石圈地幔底部温度升高,使得岩石圈底部发生热侵蚀,从而使得与软流圈接触的岩石圈地幔不断地加入到软流圈地幔;在塔里木盆地岩石圈的下部,青藏高原的岩石圈在该处发生了拆沉,从而诱发的软流圈地幔对流,上升的软流圈地幔流使得岩石圈地幔的温度升高而熔融,成为软流圈地幔。 相似文献