晋中南中新生代构造应力场演化及其动力学分析   总被引：4，自引：0，他引：4  

徐志斌  云武  王继尧  秦勇 《地学前缘》1998,(Z1)

中生代以来,晋中南经历了多期构造应力场的作用：印支期,在华北板块南北边缘造山带的强烈挤压作用下,形成了近南北方向的水平挤压应力场;燕山期,在西太平洋古陆与亚洲大陆的碰撞、拼贴作用下,形成了北西西—南东东方向的水平挤压应力场;喜山早期,受印度板块与欧亚板块碰撞作用的影响,形成了北东—南西方向的水平挤压应力场。新第三纪以来,随着裂陷沉降作用和断陷盆地深部塑性物质上涌底辟作用的增强,晋中南构造应力场演化为以北西—南东方向近水平伸展应力场为主,并且伴随着太行山和霍山的不断隆起,在晋中南东部的沁水含煤向斜中形成了局部挤压应力场。  相似文献   

长江中下游地区夏季旱涝年际、年代际变化的可能成因研究   总被引：13，自引：6，他引：13       下载免费PDF全文

李峰  何立富 《应用气象学报》2002,13(6):718-726

利用NCAR/NCEP提供的40年再分析资料和英国气象局提供的月平均海温资料及中国气象局整编的160站的降水、西太平洋副高参数资料，分析了长江中下游地区夏季降水在20世纪70年代中期前后的显著变化及其可能原因。结果指出东亚夏季风与中东太平洋海温在1976年之前关系不明显，1976年之后东亚经圈环流与低纬纬圈环流耦合紧密，加强了东亚夏季风与中东太平洋海温的联系。而20世纪70年代中期以后中东太平洋前冬的海温异常通过海洋过程影响次年夏季我国近海地区海温变化，近海海温异常作为热源强迫可以使副高位置偏南强度加强，从而造成我国长江中下游地区夏季降水偏多。  相似文献   

青藏高原东缘中南部主要活动断裂滑动速率及其地震矩亏损   总被引：9，自引：4，他引：5       下载免费PDF全文

李煜航  郝明  季灵运  秦姗兰 《地球物理学报》2014,57(4):1062-1078

作为青藏高原南东向“挤出逃逸”的重要通道,青藏高原东缘中南部具有大型走滑断裂广泛发育和地震活动强烈而频繁的特征.本文使用线性球面块体模型理论,在前人活动地块研究的基础上吸收新近研究成果,建立研究区三维块体几何模型,使用1999—2007年的GPS数据反演得到青藏高原东缘中南部主要活动断裂滑动速率.使用反演得到的滑动速率和最优断层闭锁深度估算了川滇菱形块体主要边界和其内部断裂的地震矩积累,并利用历史强震目录估算了地震矩释放,在比较两者差异的基础上得到了研究区地震矩亏损（未释放的地震矩）较大的断层和断层段,该结果可以作为研究区强震中长期危险性研究的参考.  相似文献   

高频加热中低纬电离层激励不稳定性研究   总被引：6，自引：3，他引：3       下载免费PDF全文

邓峰  赵正予  周晨  黄建 《地球物理学报》2010,53(1):10-21

高频泵波加热电离层实验二维数值模拟结果显示,虽然背景电离层状态能够明显影响模拟加热结果,但是在大部分平静电离层状态下,模拟加热一段时间后,加热区域内电子浓度、电子温度会趋于稳定,这一结论已为实验所证实.然而部分模拟结果显示,当电离层电子浓度、电子温度空间结构满足一定条件后,过密加热中泵波反射区域,电子浓度、电子温度在加热机开关机后将产生不稳定的时空效果.激发该不稳定性的正反馈过程如下：当泵波反射区域内电子温度受到泵波加热上升后,其引起的等离子体膨胀导致该区域内电子浓度减小,受到电子温度、电子浓度变化的共同影响,电子能量方程中由于电子-离子碰撞导致的电子能量损失项减小,电子温度将进一步升高,一种正反馈机制建立.最后得到以下结论,当电离层电子温度剖面呈明显的双峰结构,被加热区域内电子温度较高,且电子-离子碰撞引起能量损失项成为电子主要的能量损失项后,一种不稳定性被激发,加热将产生更明显的电子浓度、电子温度的变化.以上条件在下午电离层更容易被满足.  相似文献   

Mid–Late Cretaceous igneous activity in South China: the Qianjia example,Hainan Island     

Sai-Jun Sun  Li-Peng Zhang  Rong-Qing Zhang  Xing Ding  Hong-Li Zhu  Zhao-Feng Zhang 《International Geology Review》2018,60(11-14):1665-1683

ABSTRACT

Both Pacific and Neo-Tethys plates had major influences on the Cretaceous magmatisms in southeastern China. The subduction of the Neo-Tethys plate is, however, not well studied. This paper reports zircon U–Pb ages, Lu–Hf isotopes, whole-rock geochemistry, and Sr–Nd isotopes for the Qianjia intrusive rocks in Hainan Island, southeast China. LA-inductively coupled plasma mass spectrometry zircon U–Pb dating of granites and dark enclave monzonite in the area yield magmatic crystallization ages of ca. 100 Ma, which are consistent with other Late Cretaceous granites, e.g. Baocheng, Tunchang, and Yaliang. Both rocks show high-K calc-alkaline compositions and metaluminous to weakly peraluminous signatures belonging to I-type rocks. They are enriched in the alkalis, Rb, Th, U, K, and light rare earth elements, depleted in Nb, Ta, Ti, and P, and characterized by high Al₂O₃ contents (14–15 wt%) and high Mg^# values (50–53). Among them, some of granodiorites have geochemical affinities of adakitic rocks. Zircon ε_Hf(t) values range from ?5.97 to ?1.18, with fairly constant whole-rock Sr–Nd isotopes (I_Sr = 0.7084–0.7086; ε_Nd(t) = ?4.97 to ?4.29) similar with those of the Cretaceous mafic dikes (136–81 Ma) in Hainan Island, which are the result of partial melting of subduction-related sub-continental lithospheric mantle. Combined with Sr–Nd isotopes and negative Hf isotope, Qianjia intrusive rocks were likely derived from hybrid melts of underplated continental crust-derived with mantle-derived, then experienced varied degrees of fractional crystallization. According to the latest geophysical, sedimentological, and geochemical data, previous authors identified a Cretaceous E–W-trend subduction zone in the northern margin of the South China Sea. Combined with the southern margin magmatisms (110–80 Ma) and magmatisms of ~120 Ma distributed east–west ward from the Philippines to the Vietnam, We preferred that the subduction of the E–W-trend Neo-Tethys plate was the main geodynamic mechanism which induced the Cretaceous large-scale magmatisms in the southern margin of South China Block.  相似文献   

Retrieval of leaf water content spanning the visible to thermal infrared spectra     

《ISPRS Journal of Photogrammetry and Remote Sensing》2014

The objective of this study was to investigate the entire spectra (from visible to the thermal infrared; 0.390–14.0 μm) to retrieve leaf water content in a consistent manner. Narrow-band spectral indices (calculated from all possible two band combinations) and a partial least square regression (PLSR) were used to assess the strength of each spectral region. The coefficient of determination (R²) and root mean square error (RMSE) were used to report the prediction accuracy of spectral indices and PLSR models. In the visible-near infrared and shortwave infrared (VNIR–SWIR), the most accurate spectral index yielded R² of 0.89 and RMSE of 7.60%, whereas in the mid infrared (MIR) the highest R² was 0.93 and RMSE of 5.97%. Leaf water content was poorly predicted using two-band indices developed from the thermal infrared (R² = 0.33). The most accurate PLSR model resulted from MIR reflectance spectra (R² = 0.96, RMSE = 4.74% and RMSE cross validation RMSE_CV = 6.17%) followed by VNIR–SWIR reflectance spectra (R² = 0.91, RMSE = 6.90% and RMSE_CV = 7.32%). Using thermal infrared (TIR) spectra, the PLSR model yielded a moderate retrieval accuracy (R² = 0.67, RMSE = 13.27% and RMSE_CV = 16.39%). This study demonstrated that the mid infrared (MIR) and shortwave infrared (SWIR) domains were the most sensitive spectral region for the retrieval of leaf water content.  相似文献   

中上扬子海相层系埋藏史与构造运动的关系     

袁玉松  孙冬胜  沃玉进  周雁 《地质科学》2010,45(3):707-717

依据复杂岩性条件下孔隙度—深度关系模型,采用回剥法重建埋藏史。结果表明,中上扬子地区的埋藏史可分为3种主要类型:早抬持续型、早抬再降型和晚抬持续型。埋藏史的类型受区域构造运动控制,具有明显的分带性。齐岳山断裂以西为晚抬持续型,齐岳山断裂与黄陵隆起之间为早抬持续型,黄陵隆起以东为早抬再降型。印支运动在中上扬子地区只对海相层系有一次短暂抬升剥蚀,剥蚀量小,对埋藏史特征影响不大。燕山运动表现形式、作用强度、对海相层系的改造程度均存在明显的地区差异性,导致海相层系埋藏史类型也有地区差异性。喜马拉雅运动波及整个中国南方,但岩石圈受力性质不同,表现为西挤东张,导致K_2—E期间黄陵隆起以西持续抬升,形成"持续抬升型"埋藏史类型,以东则发生拉张断陷,形成"再降型"埋藏史类型。  相似文献