地形面方法在渭河盆地活断层研究中的应用

本文主要依据地形图和航空照片解译，并经已有地质、钻孔资料验证及野外实地考察的方法来研究地形面及其变形特征，由此确定渭河盆地活断层的分布、最新活动特征及活动规律，为地震预报及地震危险性分析提供依据。     

Dynamic recrystallization near the brittle-plastic transition in naturally and experimentally deformed quartz aggregates

The electron backscattering diffraction technique (EBSD) was used to analyze bulging recrystallization microstructures from naturally and experimentally deformed quartz aggregates, both of which are characterized by porphyroclasts with finely serrated grain boundaries and grain boundary bulges set in a matrix of very fine recrystallized grains. For the Tonale mylonites we investigated, a temperature range of 300–380 °C, 0.25 GPa confining pressure, a flow stress range of ~ 0.1–0.2 GPa, and a strain rate of ~ 10^− 13 s^− 1 were estimated. Experimental samples of Black Hills quartzite were analyzed, which had been deformed in axial compression at 700 °C, 1.2–1.5 GPa confining pressure, a flow stress of ~ 0.3–0.4 GPa, a strain rate of ~ 10^− 6 s^− 1, and to 44% to 73% axial shortening. Using orientation imaging we investigated the dynamic recrystallization microstructures and discuss which processes may contribute to their development. Our results suggest that several deformation processes are important for the dismantling of the porphyroclasts and the formation of recrystallized grains. Grain boundary bulges are not only formed by local grain boundary migration, but they also display a lattice misorientation indicative of subgrain rotation. Dynamic recrystallization affects especially the rims of host porphyroclasts with a hard orientation, i.e. with an orientation unsuitable for easy basal slip. In addition, Dauphiné twins within porphyroclasts are preferred sites for recrystallization. We interpret large misorientation angles in the experimental samples, which increase with increasing strain, as formed by the activity of fluid-assisted grain boundary sliding.     

中国台湾南部及其周边岛屿现今地壳形变的位错模型

通过建立非震形变的位错模型,用混合全局反演方法,拟合了中国台湾南部1990-1995年间的GPS观测资料.根据地质构造和地震观测,构筑了包括6个刚性块体和19个断层的简单模型.反演结果表明,菲律宾海板块以(69±2)mm/a,方向为317°±2°的速度与欧亚板块会聚,其中约一半的会聚率在台东纵谷消耗掉,另外部分则平均分配在其西边的块体交界处.菲律宾海板块和中央山脉地质区均向西北方向挤压,过了中央山脉后,块体运动呈扇形分布,与应力方向一致.西部麓山地质区与滨海平原地质区交界处的断层均以逆冲分量为主,由南向北倾角逐渐变小,断层宽度一般为10km左右,均表现为强锁定,历史上的大地震多发生在这个地区.     

The influence of stress history on the grain size and microstructure of experimentally deformed quartzite

Deformation of middle crustal shear zones likely varies with time as a result of the stress build-up and release associated with earthquakes and post-seismic deformation, but the processes involved and their microstructural signature in the rock record are poorly understood. We conducted a series of experiments on quartzite at 900 °C to characterize microstructures associated with changes in stress and strain rate, and to investigate the feasibility of carrying out grain size piezometry in natural rocks that experienced analogous changes. Differential stress (referred to simply as “stress”) was varied in two-stage experiments by changing strain rate and by stopping the motor and allowing stress to relax. The two-stage samples preserve a microstructural record that can be interpreted quantitatively in terms of stress history. The microstructure associated with a stress increase is a bimodal distribution of recrystallized grain sizes. The smaller grains associated with the second deformation stage accurately record the stress of the second stage, and the surviving coarse grains remain similar in size to those formed during the earlier stage. The transient microstructure associated with stress decrease is a “partial foam” texture containing a larger concentration of stable 120° triple junctions than occur in samples deformed at a relatively constant strain rate. Our results indicate that microstructures preserved in rocks that experienced relatively simple, two-stage deformation histories can be used to quantitatively assess stress histories.Grain growth rates during deformation are similar to rates observed in previous isostatic growth experiments, supporting theoretical approaches to recrystallized grain size, such as the wattmeter theory (Austin and Evans, 2007), that incorporate static growth rates. From an analysis of the experimental data for quartz recrystallized grain size, we find: 1) Recrystallized grain size quickly reaches a value consistent with ambient deformation conditions. We argue that this explains a good match between average grain sizes predicted by the wattmeter after complete recrystallization and the recrystallized grain sizes of the experiments. 2) The present formulation of the wattmeter overestimates the rates at which porphyroclasts recrystallize by as much as an order of magnitude, and 3) owing to problems with extrapolation of grain growth data for quartz, the wattmeter is not presently applicable to natural samples deformed at low temperatures. We present a simplified flow law for quartz, and suggest that the change in slope of the quartz piezometer at high stress (regime 1) is related to a switch to a linear viscous rheology.     

二维不均匀介质中点源P-SV波响应的有限差分近似算法

本文从一阶方程组形式的波动方程出发,发展了一种计算二维不均匀介质中点源P-SV波响应的近似方法。该方法通过引入线分布的应力作为震源,利用二维有限差分方法计算出线源响应,然后再经过波形校正和几何扩散校正得出相应的近似点源响应。通过把波形和振幅与精确解比较表明,该方法具有较好的精度。由于有限差分方法对于介质中速度和密度的分布没有特殊要求,另一方面,本文所给出的震源可以适用于位错点源、爆炸源或集中力源,因此上述方法十分适合于研究横向不均匀介质中的近场强地运动、爆炸振动或地震勘探等问题。     

云南耿马7.2级地震地表破裂带研究

根据野外考察的实际资料,本文介绍了耿马7.2级地震地表破裂带的展布,结构要素及组合、位移分布等情况。同时依据位错资料对破裂带的应力活动及断裂两盘的运动状态进行了初步分析。认为本次地震发震构造以右旋走滑为主兼具张性,主压应力优势方位为N5°—10°E。断层两盘相对运动的总体方向为N55°W左右,断层运动的滑移角在30°—40°之间     

地震断错地貌

大地震产生的断错,能改变震前的地表形态,这种改造后新出现的地形景观称为地震断错地貌。地震断错地貌可分为地震断层崖、地震断错——挠曲崖、地震断错水系和地震断错台地四类。研究地震断错的相关堆积时,发现逆推断层崖也有崩积楔。提出的崩积楔发育模式与正断层崖的发育模式截然不同。     

硬玉位错滑移系及流变学特征的研究

本文所研究的硬玉采自Ｓｅｓｉａ－Ｌａｎｚｏ带（阿尔卑斯意大利段）。该带经历了高压低温榴辉岩相变质，其变质温压为５５０℃～６００℃，１．５～１．６ＧＰａ。应用透射电子镜精细研究硬玉单晶的位错特征尚属首次，研究结果表明经天然变形的硬玉单晶中，发育有大量自由位错、位错壁、亚晶粒。自由位错密度大约为１×１０８／ｃｍ２，以刃型位错为主，也发育有少量螺位错。刃位错的伯氏矢量ｂ为［００１］和［１１０］（ｂ＝７．１６Ａ；１／２（ａ＋ｂ）＝６．６Ａ）。     

计算分层介质中位错点源静态位移场的广义反射、透射系数矩阵和离散波数方法

本文将计算合成地震图的广义反射、透射系数矩阵和离散波数方法应用于静态问题,给出了分层介质中位错点源产生的静态位移场的计算方法。该方法保留了反射、透射矩阵方法的原有优点,通过将数值结果与解析解的对比表明,该方法具有较高的数值精度,可用于研究地震断层活动造成的地表形变。     

1500年宜良地震地表形变带的考证

据历史记载１５００年在宜良一带发生了一次强烈地震，由前人对该次地震无较详细的现 场实地考查资料，因此对这次地震认识说法不一。１９９２年作者对该次地震进行了实地考证。发现和确认了这次地震十分丰富的地震地表形变带，现存长度达８１公里，最大左旋水平位错量９至１１米。研究结果表明该次地震的发震构造为小新街－徐家渡断裂，震级接近８级。