The effects of pre-existing normal faults on thrust ramp development: An example from the northern Apennines,Italy

The Umbria-Marche foreland fold-and-thrust belt in the northern Apennines of Italy provides excellent evidence to test the hypothesis of synsedimentary-structural control on thrust ramp development. This orogenic belt consists of platform and pelagic carbonates, Late Triassic to Miocene in age, whose deposition was controlled by significant synsedimentary extension. Normal faulting, mainly active from Jurassic through Late Cretaceous-Paleogene time, resulted in significant lateral thickness variability within the related stratigraphic sequences. By Late Miocene time the sedimentary cover was detached from the underlying basement and was deformed by east-verging folds and west-dipping thrusts. Two restored balanced cross sections through the southernmost part of the belt show a coincidence between the early synsedimentary normal faults and the late thrust fault ramps. These evidences suggest that synsedimentary tectonic structures, such as faults and the related lithological lateral changes, can be regarded as mechanically important controlling factors in the process of thrust ramp development during positive tectonic inversion processes.     

The transition from passive to active margin tectonics: a case study from the zone of Samedan (eastern Switzerland)

The Zone of Samedan is part of a fossil, early Mesozoic rift system originally situated in the distal, Lower Austro-Alpine domain of the Adriatic passive continental margin. An early Mesozoic configuration of asymmetrical rift basins bounded by relative structural highs compartmentalized Late Cretaceous active margin tectonics; Jurassic half-grabens were folded into arcuate synclines, whereas relative structural highs engendered thin, imbricated thrust sheets. West-directed thrusting and folding initiated at the surface and continued to depths favoring mylonitization under lower greenschist-facies conditions. At this time Liguria-Piemontese ophiolites were accreted to Lower Austro-Alpine units directly underlying the Zone of Samedan. Late Cretaceous orogenic collapse of the Adriatic active margin involved the reactivation of west-directed thrusts as low-angle, top-to-the-east, normal faults. These faults accommodated extensional uplift of Liguria-Piemontese ophiolites and Lower Austro-Alpine units beneath and within the Zone of Samedan. During Paleogene collision, some Late Cretaceous faults in the Zone of Samedan were reactivated under lower anchizonal conditions as north-directed thrusts. The latter stages of this early Tertiary thickening were transitional to brittle, high-angle normal faulting associated with top-to-the-east extension and spreading above the warm, uplifting Lepontine dome.     

论广义逆矩阵阶数增大的递推算法

本文针对加拿大地球物理学家ＥｄｏＮｇｌａｎｄ教授提出的问题，对Ｍ—Ｐ广义逆矩阵的递推算法进行了探分论述探讨的初步结果和对Ｇｒｅｖｉｌｌｅ递推算法的扩充。文中对算法的扩充给出严格的证明。     

模拟退火剩余静校正的一步算法

当地震资料的剩余静校正量大、信噪比低时，利用传统的线性反演方法不能有效地拾取静校正量。本文介绍一种非线性反演方法（一步模拟退火法）来估算炮点和检波点的剩余静校正量。通过对合成地震记录的试算表明，该算法可获得近似于真实的剩余静校正量。     

层析成像中的波形反演

在波动方程有限差分数值模拟基础上，用波形记录残差平方并建立目标函数。对目标函数进行梯度优化，我们得出了介质速度的迭代公式。通过计算目标函数梯度我们可以对介质进行速度校正，从而获得反演解。经数值试验证明这是一种很有效的反演方法。     

井间电阻率层析成象的平滑度约束反演

井间电阻率层析成象是一种探测地下浅部精细结构的物探方法，它主要用于解决工程地质问题。本文采用２．５－Ｄ有限元法，针对井间电阻率层析成象中的ＡＭ观测系统进行了反演成象计算。文中首先计算了灵敏度矩阵，然后给出了一种电阻率层析成象反演算法—平滑度约束反演，理论模型的计算和实际资料的处理，都证明了该算法的有效性     

地球物理反问题中的随机反演理论

本文从最大后验概率密度观点出发，在数据噪音向量和待求模型向量为具有零均值的独立高斯随机过程的假设前提下，建立起了随机反演的非线性系统方程；给出了模型方差估计的函数表达式，并在文章最后，证明了反演解的稀疏性，即解释了随机反演的输出解的高分辨率特征。文章在最小二乘反演方法的基础上，发展并完善了随机反演方法的理论基础；揭示了随机反演方法与最小二乘反演方法之间的本质区别；阐述了随机反演方法的优越性，并指出了其广阔的应用前景。     

中国数字地震台网的接收函数及其非线性反演

利用中国数字台网（CDSN）记录的85个远震事件的宽频带P波波形数据和分离接收函数的最大或然性反褶方法,获得了CDSN台网10个台站不同方位的岩石层接收函数.利用这些台站不同方位的平均接收函数和非线性接收函数反演方法,获得了上述各台站下方100km深度范围内的岩石层S波速度结构.结果表明CDSN台网各台站下方的地壳厚度和岩石层速度结构存在明显的差别.其中,拉萨台下方的地壳厚度为66kin,壳幔界面较模糊,而余山台下方的地壳厚度为34km,壳慢界面两侧速度反差明显.刮用本文方法估计的地壳厚度与已有的结果基本一致,由于CDSN台网覆盖了中国大陆的各主要构造单元,本文的结果为研究中国大陆的岩石层S波速度结构及其横向变化提供了新的证据.     

三维溶质运移问题的分步广义迎风解法

对对流占优的三维溶质运移问题提出了分步广义迎风解法，首先利用Ｎ．Ｎ．Ｙａ－ｎｅｎｋｏ对水动力弥散方程分步求解的思想，将原来的一个定解问题分解为两个定解问题即对流定解问题和扩散定解问题，对对流定解问题采用广义迎风对偶单元均衡法求解，对扩散定解问题采用一般的Ｇａｌｅｒｋｉｎ有限元法求解，不仅避免了用一般有限元法和有限差分法求解对流占优的地下水水质数学模型时常出现数值弥散和过量问题，而且避免了求节点速度这一步，节省运算步骤，对井点的浓度变化给出了更合适的求解方法。     

地球脉动——表现、级别及与古地磁的联系

地球脉动的概念是指地球在其历史中曾发生膨胀和收缩的周期性变化。其根据是构造变动、岩浆活动、地磁极倒转以及海平面升降等方面，在地球的膨胀和收缩期，均有各种表现。构造 海平面升降在地球收缩期形成海退，在膨胀期形成海侵。在一个地球脉动旋回的不同时期，地表、海平面和洋底之间的相互关系均有变化，因而形成“层序”的沉积记录。地磁场的强度和地磁极倒转频率在显生宙有明显变化，有高峰期和平静期。这种频率变化与构造变动和岩浆活动都有对应关系，特别是４Ｍａ为准周期的地磁极倒转频率与海底扩张、洋壳形成速率之间具有良好的对应关系。地球脉动旋回可以分为不同的级次，构成级别体系：超级旋回约１Ｇａ，巨旋回２５０～３００Ｍａ，一级旋回５０～１５０Ｍａ，二级旋回５～５０Ｍａ，三级旋回１～５Ｍａ，均可与构造旋回相对应，更高的级次对构造不形成影响。三级及更长的脉动旋回可能受深部过程的控制。中、新生代以来，地球脉动是在地球适度膨胀的背景下进行的。