琼北地区铺前−清澜断裂是一条关系到1605年琼山7½级大地震发震构造判断的重要断裂。为准确厘定该断裂的最新活动特征,针对琼北地区第四纪玄武岩盖层和巨厚海相砂沉积等地质条件,采用大吨位震源的浅层人工地震勘探和小间距钻孔联合地质剖面探测相结合的方法,分别在海口江东三江镇岐山头村和东寨村展开探测。结果表明:(1) 铺前−清澜断裂断错了多个标志地层,最浅断错至全新统烟墩组淤泥层,上断点埋深10 m左右,钻探所揭示的断层面明显具有走滑兼具逆冲性质,是一条具有一定宽度、多分支、多期次活动的大规模断裂带;(2)钻孔联合地质剖面所揭示的地层深度范围内,被断错地层的位移量随着深度增加而加大,铺前−清澜断裂自8 346~7 153 a cal BP以来有过活动,全新世累计垂直位移量4~5 m,垂直位移速率为0.53~0.63 mm/a,推断其为1605年琼山大地震的发震断裂。本研究取得的铺前−清澜断裂全新世活动的新证据,为国土空间规划和区域地震危险性评价提供了科学依据。
磁异常反演是获取地下场源磁化率分布的重要手段之一,在地球勘探中扮演着重要角色.在磁异常反演中,对比光滑反演,稀疏反演的结果具有边界分明,物性参数分布集中的特点,更符合实际情况.针对稀疏反演,本文首先构建了具有代表性的基于L1范数目标函数,利用交替方向乘子算法可分离凸函数的特点,将极小化L1范数的优化问题分解为一系列的子问题,通过对子问题求解获得原问题的解;为了增强交替方向乘子算法的适应性,本文结合广义软阈值函数将交替方向乘子法推广于Lp(0 < p < 1)范数的反演中.为了验证本文提出的算法的有效性,采用了三种常规模型进行模拟实验.与基于L2范数的反演算法进行实验对比,结果表明,本文算法得到了边界清晰,磁化率分布更集中的反演结果.最后,将基于交替方向乘子算法的L1和Lp(0 < p < 1)范数的反演应用到青海省尕林格铁矿保护区获得的实际磁异常数据中,获得了较为符合实际地质情况的稀疏反演结果.
I will argue that an ambitious programme of human space exploration, involving a return to the Moon, and eventually human missions to Mars, will add greatly to human knowledge. Gathering such knowledge is the primary aim of science, but science’s compartmentalisation into isolated academic disciplines tends to obscure the overall strength of the scientific case. Any consideration of the scientific arguments for human space exploration must therefore take a holistic view, and integrate the potential benefits over the entire spectrum of human knowledge. Moreover, science is only one thread in a much larger overall case for human space exploration. Other threads include economic, industrial, educational, geopolitical and cultural benefits. Any responsibly formulated public space policy must weigh all of these factors before deciding whether or not an investment in human space activities is scientifically and socially desirable. 相似文献
The irregular satellites of Jupiter are believed to be captured asteroids or planetesimals. In the present work is studied
the direction of capture of these objects as a function of their orbital inclination. We performed numerical simulations of
the restricted three-body problem, Sun-Jupiter-particle, taking into account the growth of Jupiter. The integration was made
backward in time. Initially, the particles have orbits as satellites of Jupiter, which has its present mass. Then, the system
evolved with Jupiter losing mass and the satellites escaping from the planet. The reverse of the escape direction corresponds
to the capture direction. The results show that the Lagrangian points L1 and L2 mainly guide the direction of capture. Prograde
satellites are captured through these two gates with very narrow amplitude angles. In the case of retrograde satellites, these
two gates are wider. The capture region increases as the orbital inclination increases. In the case of planar retrograde satellites
the directions of capture cover the whole 360° around Jupiter. We also verified that prograde satellites are captured earlier
in actual time than retrograde ones.
This paper was presented at the Asteriods, Comets and Meteors meeting held at Búzios, Rio de Janeiro, Brazil in August 2005
and could not be included in the special issue related to that conference. 相似文献