中国大陆地震活跃期和全球部分地震带强震活动的相关性研究

对全球部分地震带强震活动的研究表明，中国大陆地震活跃期与全球某些地震带强震活动呈一定程度的正相关或负相关，且有些地震带的强度震超前于中国大陆活动或平静，因此，可以利用相关地震带的强震活动和某些地震带的超前性，预测中国大陆的地震活动趋势及判定中国大陆的地震活跃期。     

Modeling the climatic effects of the land use/cover change in eastern China

This study aims to quantify the contribution of land use/cover change (LUCC) during the last three decades to climate change conditions in eastern China. The effects of farmland expansion in Northeast China, grassland degradation in Northwest China, and deforestation in South China were simulated using the Weather Research and Forecasting (WRF) model in addition to the latest actual land cover datasets. The simulated results show that when forestland is converted to farmland, the air temperature decreased owing to an increase in surface albedo in Northeast China. The climatic effect of grassland degradation on the Loess Plateau was insignificant because of the negligible difference in albedo between grassland and cropland. In South China, deforestation generally led to a decrease in temperature. Furthermore, the temperature decrease caused by the increase in albedo counteracted the warming effects of the evapotranspiration decrease, so the summer temperature change was not significant in South China. Excluding the effects of urbanization in the North China Plain, the LUCC effects across the entire region of East China presented an overall cooling trend. However, the variation in temperature scale and magnitude was less in summer than that in winter. This result is due mainly to the cooling caused by the increase in albedo offset partly by the increase in temperature caused by the decrease in evaporation in summer. Summer precipitation showed a trend of increasing–decreasing–increasing from southeast to northwest after LUCC, which was induced mainly by the decrease in surface roughness and cyclone circulations appearing northwest of Northeast China, in the middle of the Loess Plateau, and in Yunnan province at 700 hPa after forests were converted into farmland. All results will be instructive for understanding the influence of LUCC on regional climate and future land planning in practice.     

南海前新生代残留盆地分布综合地球物理研究

为了对南海海域的前新生代残留盆地分布有个整体而全面的认识,本文开展了南海残留盆地宏观分布的综合地球物理研究.通过岩石物性分析,综合重、磁、震等地球物理方法,利用正演与反演方法,分区计算并求取了南海的重力基底和磁性基底埋深,得到了中生界及前中生界残余厚度,给出了整个南海前新生代残留盆地的宏观格架与残余厚度分布特征并讨论了...     

利用福建爆破实验记录检验华南速度模型

基于2010~2012年"福建及台湾海峡地壳深部结构陆海联合探测"项目中18次爆破实验的准确发震时间、发震位置所确定的多震相走时数据,进行爆破震相特征分析,采用华南速度模型对单纯型、Hyposat、Hypo2000及Locsat等4种定位方法进行比较,得出最优定位方法。利用14炮爆破记录反演得到的速度模型与华南速度模型作比较,结果表明,反演模型的上地壳厚度小于华南模型的,下地壳厚度大于华南模型的,上地壳速度与华南模型的相当,下地壳速度大于华南模型的。利用本研究的反演结果对其他4次爆破进行重新定位,定位精度明显提高。     

福建地区环境噪声特性研究

为进一步加强对福建地区噪声特性的认识以及提升台站地震观测质量,计算了2014年福建地震台网宽频带地震仪连续观测数据的功率谱概率密度函数,并分析其影响因素和不同频段时空变化特性。结果表明:人文噪声平均水平最高地区位于福建沿海福州至厦门一带,07:00—18:00的功率谱密度要明显高于其它时间段,12:00左右出现间歇性低谷期,夜间有不同程度的降低,日变化除了在春节假期大幅下降外,均处于较为稳定态势;福建地区次级微震主要成分是Rayleigh波,主频约为2.7 s,主微震主频约为16 s,次级微震平均水平最高地区也位于沿海一带,向内陆方向呈衰减趋势,其日变化明显,与台风和潮高有较高的相关性。     

南海磁场特征研究

建立客观的磁力ΔT异常,获得可信的磁力ΔZ_⊥异常、居里面成果, 在此基础上开展综合地质地球物理研究,对于解决南海资源等相关的地质、地球物理问题意义重大.本文汇集我国历年在南海取得的磁力实测资料,重新处理、校正、整合,特别是追溯南海周边的国际地磁台的日变资料进行日变改正,形成的南海磁力ΔT异常,其资料品质得到了极大提高.采用全磁纬变倾角化极技术,获得磁力ΔZ_⊥异常,其与实测证实的磁性海山、海岛有非常好的匹配关系,建立起可以直接用于反演处理解释的南海磁力ΔZ_⊥异常.选择磁力ΔZ_⊥异常的小波多尺度分解四阶逼近,采用单一磁性界面反演技术进行深度反演,获得居里面又称磁性底界面.建立了认识、解释南海的磁场基础体系,证实了南海基性岩浆岩分布区与磁力ΔZ_⊥异常的正磁异常高密切相关,区域性的磁力ΔZ_⊥异常负磁异常区可能与居里面深度相关.     

南华北地区地震活动特征分析

南华北盆地与秦岭大别造山带在构造上有耦合关系,地震活动水平相当。将南华北盆地和秦岭大别造山带组成的南华北地区作为研究对象,考察了其地震活动特征和青藏高原强震对其影响作用。发现南华北地区地震活动水平显著低于北华北地区,略低于下扬子地区。并且,通过对比分析青藏块体7.0级以上地震和南华北地区4.0级以上地震的对应关系,发现两个地区之间存在明显的成组对应现象,并表现2年左右的时间差,表明青藏块体的地震活动对南华北地区有明显的构造应力场传递作用。该结果为南华北地区中长期地震预测提供依据。2017年四川阿坝州九寨沟县发生7.0级地震,根据时间延迟的存在,对南华北地区未来中等地震的发生具有一定的指示意义。     

Seismic anisotropy beneath the Chinese Mainland: Constraints from shear wave splitting analyses

We use earthquakes recorded by the China National Seismic Network from 2015 to 2019 and measure shear wave splitting parameters of SKS to study the anisotropic characteristics beneath the mainland of China. In general, the fast directions change from nearly E-W in western China (northwest China and Qinghai-Tibetan Plateau) to nearly N–S in central China (Ordos and Sichuan-Yunnan), and then turn to approximately E-W in eastern China (North and South China). The delay times of slow wave in eastern China are about 1.0–1.7 ​s, larger than those in central and western China (about 0.6–1.0 ​s). In addition, the fast directions in eastern China are highly consistent with the plate motion direction and horizontal GPS velocities with respect to Eurasia, indicating that the observed anisotropy is mainly from the asthenosphere which is strongly coupled to the overlying lithosphere. However, the fast directions in western China are mostly in accord with the strike of the surface structures (such as faults), possibly due to the directional arrangement of crystal lattices caused by shear deformation under tectonic activities.     

临泽断裂新活动特征初步研究

临泽断裂在地貌上可见3条断层陡坎,总体走向NNW,最长约8 km,东侧和中间陡坎主体倾向E,西侧陡坎倾向W。①利用差分GPS对3条断层陡坎进行了详细的测量,发现临泽断层陡坎较低,局部发育多级断层陡坎,坡角较缓,高度几十厘米至1米多;②在临泽断裂上选取4个探槽剖面进行古地震分析、样品采集和年代测试,发现东侧和中间的断层陡坎为正断层所控制,西侧的断层陡坎为逆断层所控制;③探槽开挖揭露出晚更新世晚期以来,临泽断裂上发生过4次古地震事件,时间分别为(8 895±125)a B.P.之前、(7 245±75)a B.P.～(6 190±20)a B.P.、(5120±20)a B.P.～(4.8±0.5)ka和(2 550±50)a B.P.～(2 326±64)a;④全新世以来可以确定3次事件,较早一次事件与榆木山北缘断裂上较早一次古地震事件时间比较吻合,说明临泽断裂可能是榆木山断裂向河西走廊内部继续活动的延伸;最后一次古地震事件的离逝时间约为2 500 a,表明临泽断裂全新世活动一直比较强烈。     

Paleogeography of the North and South China blocks during the Cambrian

Paleomagnetic results demonstrate that during the Cambrian the South China block was close to the equator. We suggest that it was adjacent to North Australia. This reconstruction juxtaposes Cambrian marine basins in South China and Australia, explaining the affinity between Cambrian trilobites from the two areas, as well as the existence of phosphorite deposits in the Early and Middle Cambrian in Australia and in South China. The stratigraphic similarity between the late Precambrian Sinian System in South China and the Adelaide System in Australia, and the continuing fossil affinities from Cambrian through Ordovician of both areas suggest that the proposed geographic configuration lasted from the late Precambrian (800 Ma) to Early Ordovician (470 Ma). Paleomagnetic results from the Cambrian of North China indicate that it was in the southern hemisphere at that time. Based on the paleontological evidence, we suggest that the North China block was close to Tibet, Iran and northern India during the Paleozoic.     

中国海地球物理场特征

1960年开始对中国海进行地球物理系统调查,经过30年积累了丰富的测控、重力、磁力和地震资料,应用“一、二、三、多”的综合解释原则,编绘并出版了比例尺为1：5M的“中国海区及领域地质地球物理系列图”（1992）,在此基础上,认识到中国海的一些地球物理现象,进而讨论了中国大地构造格架及其演化历史,提出了中国对海底油气资源的看法。     

地磁正常场的选取与地磁异常场的计算

根据2003年中国地磁观测数据（包括135年地磁测点和35个地磁台）以及我国邻近地区38个IGRF计算点的地磁数据,计算中国地磁异常场的分布。选取两种地磁场模型作为地磁正常场,一是国际参考地磁场的球谐模型,二是中国地磁场泰勒多项式模型。根据各个测点的地磁异常值（观测值减去模型计算值）,用球冠谐分析方法计算地磁异常场的球冠谐模型,并绘制2003年中国地磁异常（△D,△I,△F,△X,△Y,△Z）。分析和讨论了中国地磁异常场。     

Forecasting the summer rainfall in North China using the year-to-year increment approach

A new approach to forecasting the year-to-year increment of rainfall in North China in July–August (JA) is proposed. DY is defined as the difference of a variable between the current year and the preceding year (year-to-year increment). NR denotes the seasonal mean precipitation rate over North China in JA. After analyzing the atmospheric circulation anomalies associated with the DY of NR, five key predictors for the DY of NR have been identified. The prediction model for the DY of NR is established by using multi-linear regression method and the NR is obtained (the current forecasted DY of NR added to the preceding observed NR). The prediction model shows a high correlation coefficient (0.8) between the simulated and the observed DY of NR throughout period 1965–1999, with an average relative root mean square error of 19% for the percentage of precipitation rate anomaly over North China. The prediction model makes a hindcast for 2000–2007, with an average relative root mean square error of 21% for the percentage of precipitation rate anomaly over North China. The model reproduces the downward trend of the percentage of precipitation rate anomaly over North China during 1965–2006. Because the current operational prediction models of the summer precipitation have average forecast scores of 60%–70%, it has been more difficult to forecast the summer rainfall over North China. Thus this new approach for predicting the year-to-year increment of the summer precipitation (and hence the summer precipitation itself) has the potential to significantly improve operational forecasting skill for summer precipitation. Supported by National Basic Research Program of China (Grant No. 2009CB421406), National Natural Science Foundation of China (Grant Nos. 40631005, 40775049) and Excellent Ph. D Dissertation in Chinese Academy of Sciences     

南海东北部滨海断裂带的研究现状与展望

南海东北部滨海断裂带由于其在南海中所处的特殊地理位置及在华南沿海和南海北部陆架两个构造区域中的重要作用，一直倍受中外地球工作者关注。本文总结了滨海断裂带地球物理方面的最新研究成果及目前所存在的问题，阐明了滨海断裂带两测地壳结构特征明显不同，并特别指出，加强滨海断裂带深部结构研究，同时综合周边已知的地球物理资料，解决滨海断裂带的构造属性问题、中地壳低速层问题及探讨滨海断裂带与地震活动性的关系是今后的研究重点与突破方向。     

雁荡山湖泊沉积物记录的中国东部季风区小冰期以来气候干湿变化

中国东部季风区过去千年降水变化特征已有大量研究并取得重要进展,但多数研究集中在中国北方和中部地区,南方地区重建记录相对较少.本文对浙江雁荡山雁湖沉积物的总有机碳、色度和粒度等多指标进行分析,重点探讨小冰期以来研究区域的降水变化,结果显示:1)1400-1600 AD,湖区集水发育,研究区气候偏湿润;2)1600-1650 AD,降水量减少,气候偏干旱;3)1650-1750 AD,气候偏湿润;4)1750-2000 AD,研究区气候处于干旱状态,其中1500-1650 AD期间的干湿变化与历史文献记录的雁湖水位有良好的对应关系.在年代误差范围内,雁湖沉积物与浙江天目山泥炭、福建仙山泥炭以及湖光岩玛珥湖沉积物等记录的干湿变化同步,指示了小冰期期间中国东南地区气候波动的一致性.另外,中国东部南、北地区古气候记录反映的降水变化趋势相反,表明在百年时间尺度上,中国东部南北地区降水存在着"南涝北旱"和"北涝南旱"的空间特征.通过与太平洋年代际振荡(PDO)的对比,显示PDO对中国东部地区小冰期期间出现的南-北"偶极型"空间降水特征可能具有重要影响.     

Observational study of the physical and chemical characteristics of the winter radiation fog in the tropical rainforest in Xishuangbanna,China

Science China Earth Sciences - We conducted a three-month field experiment focusing on the physical and chemical characteristics of fog in a tropical rainforest in Xishuangbanna, Southwest China,...     

汶川大地震前非台风扰动现象的研究

为了区分汶川大地震的震前扰动现象中的台风因素和非台风因素,本文研究了中国大陆宽带地震仪在汶川大地震前记录到的异常扰动信号的时频特征.研究结果表明汶川大地震的震前扰动主要由两种扰动构成,二者动态特征完全不同.其中优势频率为0.2～0.25 Hz的扰动主要与台风Rammasun有关.这种台风扰动在沿海地区较强,在内陆地区较弱,其震动源在靠近台风运动路径的海底.另一种优势频率为0.1～0.18 Hz的扰动与台风无关,这种非台风扰动在地震发生前约10 h突然急剧增强,其最大值出现在地震爆发时刻.非台风扰动在靠近震中的地区较强,在沿海和西部地区较弱.震源扰动扫描算法计算初步定位的结果显示其震动源不在海底,而是分散在震中附近的内陆地区.汶川大地震前的非台风扰动是否与汶川大地震有关,值得进行更深入的研究.     

中国地震前兆台网主要问题探讨

通过“十五”中国数字地震观测网络项目建设,中国地震前兆台网的建设和运行维护取得了巨大的进步,但也存在一些不足之处。本文从观测、运行和服务等几个方面对中国地震前兆台网存在的一些不足之处进行了全面分析总结,提出了对这些问题的解决方法,以供今后前兆台网建设时参考。     

褶皱冲断带时空演化动力学过程的数值模拟

利用库仑临界锥角理论和沙箱物理模拟进行褶皱冲断带的研究时,通常忽略了楔形体介质的内聚力.岩石力学实验结果表明,岩石内聚力通常在几到几十兆帕范围内变化.楔形体介质强度的变化是否会影响褶皱冲断带的时空演化?针对这一问题,我们建立了岩石内聚力分别是10MPa、20MPa和50MPa的3个二维弹塑性有限元模型,模型包含了楔形体介质的弹塑性材料非线性和底部滑脱带的接触非线性.该模型考虑了不同介质强度、底部滑脱带摩擦、重力和边界构造加载的影响,更为符合实际.计算结果表明,岩石内聚力为10MPa时,楔形体内的断坡首先在楔形体近端产生,从近端依次向远端发展;岩石内聚力是20MPa时,断坡开始在楔形体近端产生,随后在远端也开始形成,最后由两端向中间汇聚;岩石内聚力是50MPa时,断坡先从楔形体远端形成,从远端向近端依次发展.我们还讨论了底部滑脱层倾角对褶皱冲断带演化的影响,结果表明较低的底部滑脱面倾角易产生由近端向远端演化的样式,中等滑脱面倾角易产生两端向中间演化的样式,较高滑脱面倾角易产生由远端向近端演化的样式.我们得到了三种不同的褶皱冲断带时空演化的模式,其结果可以用来解释青藏高原东北缘依次向北东方向发展的海原-六盘山断层、天景山断层、烟筒山断层系统的时空演化.     

Characteristics of Horizontal Crustal Movement in the North China Region in the Last Decade

Based on high-precision data obtained in the past decade from GPS re-measurement in the North China Network, the Crustal Movement Observation Network of China (CMONOC) and GPS measurement along the Shanxi graben zone, the status and evolution of horizontal crustal movement in the North China region are analyzed. The results show that (1) the Yanshan tectonic zone (Zhangjiakou-Bohai Sea zone)is an active one with the largest horizontal strain in the North China region; The largest tendency differential movement of adjacent blocks is seen between the Yanshan block and the North China plain block; about 2mm/a (left lateral) ; (2)The significant horizontal differential movement along the boundaries of the North China region is characterized by right-lateral strike-slip movement at the middle-north segment on its west boundary (composed of Yinchuan and other active tectonic zones) and compressive movement at the south segment; while the Yinshan rift zone located along the west segment on its north boundary is dominated by tensile movement. Other boundaries and zones have no obvious differential movement; (3) On the whole, measurements of each period differ from one another, which might result from the nonlinear movement component as well as from the error effect. In the paper, results of the relative movement and strain in different periods are given for different blocks and boundary zones.