震源耦合的等效物理模型

本文提出了考虑各潜在震源相互耦合的等效物理模型，系统地建立了通过拟合各潜在震源地震序列来确定不同时间段内活断层形速率的方法，给出了预报各潜在震源未来一定年限内发生震级在不同震级段的概率模型。     

Study on the sources of some deep focus earthquakes in Northwest Pacific region

The sources for thirteen deep focus earthquakes ofm _b≥5.5 andh>400 km in Northwest Pacific region were studied using waveform fitting and shear fracture source model. The source parameters were obtained as follows: focal depth, faulting plane, slip direction, rupture velocity, rupture length, rupture direction and scalar moment tensor. It was found that all these earthquake sources can be interpreted as shear faulting and have simple source time functions. The strike direction of faulting plane for most deep focus earthquakes coincides with that of the subduction zone, especially in the deep part of the subduction zone, it results in the tendency of reducing the dip angle of the subduction zone. The multiple point source model was also used to study the source process. The waveform fitting is better than the shear fracture model, but the general rupture direction which coincides with that from unilateral shear source model can not be obtained from the multiple point source model. This study is supported by the National Science Foundation of China and the Chinese Joint Seismological Science Foundation.     

An effective approach to determine the dynamic source parameters

In this study, we present a new and effective method to determine the dynamic source parameters (i.e., stress drop and strength distribution). We first assume that the kinematic source parameters, i.e., the slip and rupture time distributions on the fault plane, are known from the previous source inversion studies. Then, using the seismic source representation theorem we determine the dynamic stress field on a fault plane from known kinematic parameters. Finally, we determine the strength of the fault defined as the peak stress just before the rupture. We have tested the validity of this method by using an illustrative two-dimensional analytical example. To assess the applicability of this method, we have applied it to study the 1979 Imperial Valley earthquake, and obtained consistent results with those ofMiyatake's (1992) andQuin's (1990). Compared with previous methods, this new method is simple, straightforward and accurate, and needs much less calculation. Therefore, it is expected to be useful in exploring the seismic source process.     

塔里木盆地陆相烃源岩有机组分的分类及其岩石学特征

通过对塔里木盆地陆相烃源岩所作的详细有机岩石学研究，提出了适合该盆地的陆相烃源岩有机组分分类方案，并系统地阐述各有机组分的光性、成因及岩石学特性。     

宏观地震忽略吸收确定震源深度问题的通解及其精确度

分析G-R-闵公式后得出,它是从点源幅射场导出的,与地震宏观场不相应。因在近场震源不能视作点源。在分析过程中,导出相当于点源、线源或面源以及复杂源的幅射场的深度公式。对实际的地震,它的源类型一无所知,所以不预作假定,将源指标几何扩散率n作为待定参数,导出了一个物理意义明确而又普遍化的震源深度公式。此公式的诸解法中,以计算方法准确、精度高,作图法有直观的优点,但准确性差、精度低,图算法只作获取粗略值和考察数据均匀性用。计算了9个8级以上巨震、1个71/2大震,和两个M_L=3的有感地震的震源深度,经对比结果很好,利用计算得出震源类型,结合宏观场研究了这些地震的震源几何学。并且首次在国际上给出宏观地震震源深度值的标准误差。     

The reservoir-associated earthquakes of April 1983 in western Thailand: Source modeling and implications for induced seismicity

On 22 April 1983, a very large area of Thailand and part of Burma were strongly shaken by a rare earthquake (m _b=5.8,M _s=5.9). The epicenter was located at the Srinagarind reservoir about 190 km northwest of Bangkok, a relatively stable continental region that experienced little previous seismicity. The main shock was preceded by some foreshocks and followed by numerous aftershocks. The largest foreshock ofm _b=5.2 occurred 1 week before the main shock, and the largest aftershock ofm _b=5.3 took place about 3 hours after the main shock. Focal mechanisms of the three largest events in this earthquake sequence have been studied by other seismologists using firts-motion data. However, the solutions for the main shock and the largest aftershock showed significant inconsistency with known surface geology and regional tectonics. We reexamined the mechanisms of these three events by using teleseismicP-andS-waveforms and through careful readings ofP-wave first motions. The directions of theP axes in our study range from NNW-SSE to NNE-SSW, and nodal planes strike in the NW-SE to about E-W in agreement with regional tectonics and surface geology. The main shock mechanism strikes 255°, dips 48°, and slips 63.5°. The fault motions during the main shock and the foreshock are mainly thrust, while the largest aftershock has a large strike-slip component. The seismic moment and the stress drop of the mainshock are determined to be 3.86×10²⁴ dyne-cm and 180 bars, respectively. The occurrence of these thrust events appears to correlate with the unloading of the Srinagarind reservoir. The focal depths of the largest foreshock, the main shock, and the largest aftershock are determined to be 5.4 km, 8 km, and 22.7 km, respectively, from waveform modeling and relative location showing a downward migration of hypocenters of the three largest events during the earthquake sequence. Other characteristics of this reservoir-induced earthquake sequence are also discussed.     

四川冕西稀土成矿区的地质特征及其远景探讨

笔者从区域地质条件、矿床地质特征、冕西岩体性质、稀土模式、主要稀土矿物特征以及矿石的工艺性质进行了考查,并作了区域性对比。初步认为,在冕西地区以碱长花岗体为主体,形成了面积近800km~2的稀土成矿区。霓石碱性花岗岩-构造破碎带-碱性(伟晶)岩脉是区内稀土成矿的基本要素,也是最直接的找矿标志,围绕冕西岩体出露的卫星式霓石碱性花岗岩有着不同于A型碱长花岗岩的稀土模式,是稀土成矿矿源体。不同产地的稀土矿物特征、矿石矿物组合和矿石类型均有很好的可比性,属易采易选优品级稀土矿石。在该区有必要进一步开展矿产普查工作。     

新疆喀拉通克铜镍矿贵金属矿物定量研究

喀拉通克铜镍矿床产于漏斗状基性岩体中下部的橄榄苏长辉长岩相中,矿石类型分特富铜镍矿石(Ⅰ)、富铜贫镍矿石(Ⅱ)、贫铜贫镍矿石(Ⅲ)及富镍富铜矿石(Ⅳ).由于矿床物质成分复杂特别是金银铂钯矿物颗粒细、品位低、种类多,故首先在进行矿物定性研究的基础上,确定目的矿物的特殊富集流程.然后在人工重砂大样中富集目的矿物,并制成砂光薄片,有代表性的排定视域,引入电子探针-图象分析-计算机联机定量并辅以显微镜定量的综合方法对贵金属元素和矿物进行定量.联机方法是用电子探针以扫描方式提供颗粒电子象和元素X射线面分布象信号给出元素或共存元素的化学信息,对矿物颗粒进行分类,统计出个数及面积百分比.这种方法对微细杂矿物的定量工作颇有成效.     

Pore fluid pressure effects in anisotropic rocks: Mechanisms of induced seismicity and weak faults

Many observations and studies indicate that pore fluid pressure in the crustal rocks plays an important role in deformation, faulting, and earthquake processes. Conventional models of pore pressure effects often assume isotropic porous rocks and yield the nondeviatoric pressure effects which seem insufficient to explain diverse phenomena related to pore pressure variation, such as fluid-extraction induced seismicity and crustal weak faults. We derive the anisotropic effective stress law especially for transversely-isotropic and orthotropic rocks, and propose that the deviatoric effects of pore fluid pressure in anisotropic rocks not only affect rock effective strength but also cause variation of shear stresses. Such shear stress variations induced by either pore pressure buildup or pore pressure decline may lead to faulting instability and trigger earthquakes, and provide mechanisms for the failure of crustal weak faults with low level of shear stresses. We believe that the deviatoric effects of pore fluid pressure in anisotropic rocks are of wide application in studies of earthquake precursors and aftershocks, oil and gas reservoir characterization, enhanced oil recovery, and hydraulic fracturing.