利用重力资料研究华北地区构造应力场

本文结合相关数据、模型和软件分别利用重力场、重力垂线偏差与构造应力场的内在关系式对华北地区陆地构造应力值进行了计算,通过对相关数据结果进行对比分析,总结并得出了华北地区重力总水平梯度、构造应力场和研究方法本身的一些规律和特征。     

北印度洋越赤道经向翻转环流的年际变化

利用50a(1950~1999)的SODA资料对北印度洋(7°S以北)越赤道的经向翻转环流及其年际变化进行了研究。结果表明,就年平均而言,上层向北的入流在越过赤道后最终通过Ekman层向南返回构成环流圈;在赤道附近的混合层,表层存在与Ekman流相反的流动。向北的入流主要通过西边界流实现,深度可达500m,向南的流动在西部较强。此环流有很明显的年际变化,周期约为4a;它的变化与海面风应力的变化是密切相关的。提出了反映此环流年际变化的2个指数。     

当涂地震站震级偏差分析

选取当涂地震站2015年12月至2020年4月记录的120个1.2相似文献   

上海地震台阵面波震级偏差分析

通过计算功率谱密度来讨论上海地震台阵所测远震面波震级与美国国家地震信息中心(NEIC)震级的差别,对不同震级、不同方位和不同震中距的地震震级差别进行了比较和讨论,并给出初步结果.     

一种震前超低频密度——应力波

地震发生前天文时纬残差观测数据出现异常,得到了不同天文台观测结果的证实。另外,两种与地震相关的物理量震前地下深部物质视电阻率变化和断层活动矩变化,其物理机制的解释以及与后续地震的关联方式和天文时纬残差有很多共性。而且,这3类观测现象与后续地震的关联方式与国外学者提出的热力学弹性回跳模型符合得很好。本文基于现有观测证据和理论模型的一致性,提出地震前在地层构造中存在一种来自孕震区域的超低频密度—应力波。     

天津测震台网各子台震级偏差浅析

选取了2002—2005年天津台网记录的100个地震速报事件,利用NEDisa软件重新进行分析处理,根据定位结果对天津各台站的震级数据资料进行整理、归类分析,计算出每个地震各台站与台网平均震级的偏差和各台的多个地震的震级平均偏差。根据速度震级公式中震级的影响因素,主要从量规函数和台基两方面进行震级偏差原因分析,给出了各台的台基校正值,台基校正后震级偏差统计表。结果显示天津台网现采用的量规函数在震中距0~20 km内对震级偏差稍有影响,其他范围内影响不大;而台基对震级偏差影响较大,对天津台网各子台进行台基校正是很必要的。     

轨道几何特征匹配列车定位方法

轨道不平顺和轨距偏差等几何特征是直接反映轨道质量优劣的信息,它们均是轨道里程的函数,包含了丰富和低成本的位置信息,在重复观测中具有一致性。本文对轨道几何特征匹配列车定位方法的可行性进行了评估,建立了存储于计算机的背景数据库,然后通过采集待匹配数据和背景数据库进行匹配比对,获得了满足精度要求的列车位置。该方法为多传感器融合的列车控制系统提供了一种新的定位信息和思路,可以作为提高列车定位系统稳健性的辅助手段。     

Contributions of the Bering Strait throughflow to oceanic meridional heat transport under modern and Last Glacial Maximum climate conditions

Paleo reconstructions and model simulations have suggested the Bering Strait plays a pivotal role in climate change. However, the contribution of the Bering Strait throughflow to oceanic meridional heat transport (OMHT) is about 100 times smaller than the OMHT at low latitudes in the modern climate and it is generally ignored. Based on model simulations under modern and Last Glacial Maximum (LGM,~21 ka;ka=thousand years ago) climate conditions, this study highlights the importance of the Bering Strait throughflow to OMHT. The interbasin OMHT induced by the Bering Strait throughflow is estimated by interbasin-intrabasin decomposition. Similar to barotropic-baroclinic-horizontal decomposition, we assume the nonzero net mass transport induced by interbasin throughflows is uniform across the entire section, and the interbasin term is separated to force zero net mass transport for the intrabasin term. Based on interbasinintrabasin decomposition, the contribution of the Bering Strait throughflow is determined as ~0.02 PW (1 PW=10 15 W) under the modern climate, and zero under the LGM climate because the closed Bering Strait blocked interbasin throughflows. The contribution of the Bering Strait throughflow to OMHT is rather small, consistent with previous studies. However, comparisons of OMHT under modern and LGM climate conditions indicate the mean absolute changes are typically 0.05 and 0.20 PWin the North Atlantic and North Pacific, respectively. Thus, the contribution of the Bering Strait throughflow should not be ignored when comparing OMHT under diff erent climate conditions.     

The seasonal variation of the North Pacific Meridional Overturning Circulation heat transport

Based on the 50-year Simple Ocean Data Assimilation (SODA) reanalysis data, we investigated the basic characteristics and seasonal changes of the meridional heat transport carried by the North Pacific Meridional Overturning Circulation. And we also examined the dynamical and thermodynamic mechanisms responsible for these heat transport variability at the seasonal time scale. Among four cells, the tropical cell (TC) is strongest with a northward heat transport (NHT) of (1.75±0.30) PW (1 PW=1.0×10^15 W) and a southward heat transport (SHT) of (-1.69±0.55) PW, the subtropical cell (STC) is second with a NHT of (0.71±0.65) PW and SHT of (-0.63±0.53) PW, the deep tropical cell (DTC) is third with a NHT of (0.18±0.03) PW and SHT of (-0.18±0.11) PW, while the subpolar cell (SPC) is weakest with a NHT of (0.09±0.05) PW and SHT of (-0.07±0.09) PW. These four cells all have diff erent seasonal changes in their NHT and SHT. Of all, the TC has stronger change in its SHT than in its NHT, so do both the DTC and SPC, but the seasonal change in the STC SHT is weaker than that in its NHT. Therefore, their dynamical and thermodynamic mechanisms are diff erent each other. The local zonal wind stress and net surface heat flux are mainly responsible for the seasonal changes in the TC and STC NHTs and SPC SHT, while the local thermocline circulations and sea temperature are primarily responsible for the seasonal changes of the TC, STC and DTC SHTs and SPC NHT.     

不同大西洋经圈翻转环流平均强度下中国气候的年代际响应特征

基于美国大气研究中心的CCSM3(Community Climate System Model version 3)模式,对淡水扰动试验中不同大西洋经圈翻转环流(Atlantic Meridional Overturning Circulation,AMOC)平均强度下,中国气候的年代际响应特征进行研究。结果表明:在年代际尺度上,中国区域地表气温和降水强度变化与AMOC强度变化的关系紧密,然而,不同平均强度下,中国气候的年代际响应特征不同。高平均强度下,中国区域地表气温升高,中国北部降水增多、南部降水减少;低平均强度下,则反之。不同平均强度下,中国区域年平均地表气温和降水EOF第一特征向量的空间分布存在显著差异:高平均强度下,地表气温呈现中国全区域一致的分布型,降水呈现自北向南的"-+-"型的雨带分布;低平均强度下,地表气温呈现中国区域南北反相的偶极子分布型,降水呈现自北向南的"-+"型的雨带分布。与低平均强度相比,在高平均强度下,EOF第一模态的时间系数的年代际变化尺度均更长。