Three-dimensional thermo-rheological structure of the lithosphere in the North China Craton determined by integrating multiple observations: Implications for the formation of rifts

The lithosphere of the North China Craton(NCC) has experienced significant destruction and deformation since the Mesozoic, a notable feature of which is the widespread extensional structure and lithospheric thinning in the eastern NCC. Since the thermo-rheological structure of the lithosphere is one of the main factors controlling these dynamic processes, a threedimensional thermo-rheological model of the present lithosphere in the NCC was developed based on a geophysical-petrological method using a variety of data, and its relationship with the extensional structures and the formation of rifts was further analyzed.Our results show that the western NCC is characterized by thick lithosphere, low Moho temperature(T_(Moho)600°C), as well as high lithospheric strength and mantle-crust strength ratio(S_m/S_c1). The deformation of the western narrow rift is consistent with the localized deformation dominated by the strength of lithospheric mantle. On the other hand, the lithosphere in the eastern NCC is characterized by extensive thinning(with lithospheric thickness of about 80–110 km). However, the decrease of lithospheric strength is not uniform, with high strength(10×10~(12) Pa m) observed in some areas(such as the Bohai Bay Basin and Hehuai Basin). Most of the eastern lithosphere is characterized by high TMoho(600–750°C) and low S_m/S_c(1), which is inconsistent with the widespread extensional structure in the eastern NCC. Incorporating results from palaeo-geothermal and petrological studies,we developed a thermo-rheological structure model of the lithosphere at different evolutionary stages of the NCC, and suggested that the eastern NCC had a significantly thinned and weakened lithosphere in the early stages of the formation of the rift, leading to a regional distributed extension deformation dominated by crustal strength, which eventually evolved into a series of wide rifts. However, the cooling and accretion of the lithosphere in the subsequent stages significantly increased the strength of the lithospheric mantle, resulting in the inconsistency between the present thermo-rheological structure of the lithosphere and the extensional structure formed in the past.     

确定坡面径流过程曼宁糙率系数的实验方法研究

曼宁糙率系数是用水动力学方法进行流速计算的关键参数。坡面流曼宁糙率系数与明渠流的不同。为确定坡面径流过程的曼宁糙率系数,自行研发了一种包括供水系统、实验水槽和数据观测记录系统的室内可变糙率坡面实验系统。通过87场预实验验证了供水系统的稳定性和准确性。以坡度、实测流量、实测水深、不同糙率板上河砂的平均直径和地表粗糙度为自变量,以曼宁糙率系数为因变量,选用均方根误差(RMSE)和决定系数(R ²)为评价指标,对166种实验场景进行了支持向量机(Support Vector Machines, SVM)训练与预测,发现：① 紊流的训练结果难以预测层流和过渡流的曼宁糙率系数,说明流态不同时,实验因素对水流的影响机制不同;② 若要较为准确地预测曼宁糙率系数,至少需要包括实测水深在内的3种因素;③ 当同时考虑4种及更多种因素时,紊流状态下均可对曼宁糙率系数进行较为准确的预测。     

北京市突发地质灾害监测预警系统设计与实现

北京市突发地质灾害监测预警系统功能覆盖了灾害调查、监测、分析、预警、应急管理工作的全流程.该系统在设计中采用了诸多关键技术:用基于地质要素分类的监测方法来解决单纯按对象分类监测方法而产生的数据使用局限问题;针对结构化、非结构化、空间的各类监测预警数据采用三重分类并分别集成的方法来解决地质信息系统普遍存在的多源异构数据存储利用的问题;用建立统一通讯规约的方法来解决设备数据接收和管理的问题;用分灾种、分时空精度、分方法建立预警模型库的方式来解决预警模型合理性、准确性和时效性的问题.