关于变形极坐标法的应用

讨论了变形极坐标法的观测、计算和精度分析,给出了供应用的待定点点位中误差实用的计算式和点位误差等值线图。同时,对该法的应用提出了几点建议,供实际作业参考和应用。     

香溪河流域白家堡滑坡变形监测初步分析

白家堡滑坡受三峡大坝蓄水及强降雨影响变形较为明显,且仍在变形过程中。利用GDM600S型全站仪及cx-03D型钻孔测斜仪分别对滑坡地表及滑坡深部位移进行监测。监测结果表明:白家堡滑坡体呈"D"型整体运动;滑坡后缘滑动面(带)和中部滑动面(带)分别在地下11m和28.5m左右;滑坡整体滑动方向大致为NE55°,且滑坡变形具有自后缘向前缘递减的趋势。     

RESEARCH OF SEISMOGENIC STRUCTURE OF THE MENYUAN MS6.4 EARTHQUAKE ON JANUARY 21, 2016 IN LENGLONGLING AREA OF NE TIBETAN PLATEAU

On January 21 2016, an earthquake of M_S6.4 hit the Lenglongling fault zone(LLLFZ)in the NE Tibetan plateau, which has a contrary focal mechanism solution to the Ms 6.4 earthquake occurring in 1986. Fault behaviors of both earthquakes in 1986 and 2016 are also quite different from the left-lateral strike-slip pattern of the Lenglongling fault zone. In order to find out the seismogenic structure of both earthquakes and figure out relationships among the two earthquakes and the LLLFZ, InSAR co-seismic deformation map is constructed by Sentinel -1A data. Moreover, the geological map, remote sensing images, relocation of aftershocks and GPS data are also combined in the research. The InSAR results indicate that the co-seismic deformation fields are distributed on both sides of the branch fault(F₂)on the northwest of the Lenglongling main fault(F₁), where the Earth's surface uplifts like a tent during the 2016 earthquake. The 2016 and 1986 earthquakes occurred on the eastern and western bending segments of the F₂ respectively, where the two parts of the F₂ bend gradually and finally join with the F₁. The intersections between the F₁ and F₂ compose the right-order and left-order alignments in the planar geometry, which lead to the restraining bend and releasing bend because of the left-lateral strike-slip movement, respectively. Therefore, the thrust and normal faults are formed in the two bending positions. In consequence, the focal mechanism solutions of the 2016 and 1986 earthquakes mainly present the compression and tensional behaviors, respectively, both of which also behave as slight strike-slip motion. All results indicate that seismic activity and tectonic deformation of the LLLFZ play important parts in the Qilian-Haiyuan tectonic zone, as well as in the NE Tibetan plateau. The complicated tectonic deformation of NE Tibetan plateau results from the collisions from three different directions between the north Eurasian plate, the east Pacific plate and the southwest Indian plate. The intensive tectonic movement leads to a series of left-lateral strike-slip faults in this region and the tectonic deformation direction rotates clockwise gradually to the east along the Qilian-Haiyuan tectonic zone. The Menyuan earthquake makes it very important to reevaluate the earthquake risk of this region.     

2016年台湾美浓MW6.4地震震源参数的InSAR和GPS反演

2016年2月6日台湾西南部高雄市美浓区发生了M_W6.4地震.本文结合ALOS2卫星升降轨、Sentinel-1A升轨SAR数据,采用两轨差分干涉技术获取了该区域的同震形变场,形变结果表明震中西北部以抬升为主,最大视线向形变量约为11.2 cm.基于均匀位错模型和多峰值粒子群（MPSO）算法,利用InSAR和GPS形变数据联合反演了美浓地震的断层几何参数,结果表明震源中心位于22.920°N,120.420°E,深度约12 km,发震断层长度约15 km,走向角307°,倾角16.5°,平均滑动角为51.5°,此次地震是以逆冲倾滑兼左旋走滑的破裂模式.利用格网迭代搜索法得到最优倾角为15.7°,GPS和InSAR最优权比为18：1,最优平滑因子为0.06.基于非均匀位错模型,利用非负最小二乘方法进行线性反演,结果显示最大倾滑和走滑量分别为51.7 cm和55.3 cm,对应矩震级为M_W6.38,略小于GCMT （M_W6.4）的结果.通过与已有文献的比较和对该区域断层构造的分析,发现美浓地震的发震断层为单一断层的解释更为合理,我们推测发震断层是位于左镇、后甲里等断层之间的一条东南-西北走向往东北倾斜的盲断层,并初步推测2010年M_W6.3甲仙地震也同该断层有关.     

Residual slip of sliding blocks induced by near‐fault ground motions

The response of a rigid block supported on a horizontally moving foundation through a dry‐friction contact is investigated to near‐fault ground motions. Such motions can be thought of as consisting of a coherent component (‘pulse’) and an incoherent component, which can be described as a band‐limited ‘random noise’. The equation of motion of this strongly nonlinear system is reduced to a normalized form that reveals important parameters of the problem such as the critical acceleration ratio. The response of the sliding block to a set of uniformly processed near‐fault motions, covering a sufficiently wide range of magnitudes, is evaluated numerically for selected discrete values of the acceleration ratio. For each value of the critical acceleration ratio, the numerically computed residual slips are fitted with a Weibull (Gumbel type III) extreme value probability distribution. This allows the establishment of regression equations that describe accurately design sliding curves corresponding to various levels of non‐exceedance probability. The analysis reveals that the coherent component of motion contributes significantly to the response of the sliding block. Furthermore, the relevant acceleration in specifying the critical acceleration ratio is the (normalized) amplitude, α_{H_pulse}, of the pulse and not the (normalized) amplitude of the incoherent component α_H. Finally, the incoherent component is described quantitatively in terms of the root‐mean‐square acceleration a_RMS, and an attempt is made to understand its influence on the response of the sliding block. Copyright © 2016 John Wiley & Sons, Ltd.     

软土动力特性动三轴试验研究

许多学者对软土在动力作用下的变形特性进行了大量的研究,并提出了相应的经验公式,但其经验公式参数较多且试验复杂,不易被一般工程技术人员掌握运用。本文采用天津滨海地区软土为研究对象,进行钻探取样、波速测试、室内静力学和动三轴试验,获取该地区软土的静、动力学参数,并利用相对简单的模型对残余应变和软化指数随振次的变化规律采用最小二乘法进行拟合,取得很好的效果。成果表明,利用简单的模型对软土的动力特性进行区域性研究是可行的。该成果可为今后软土动力特性和软土震陷计算方法研究提供参考和基础性资料。     

青海钻孔应变映震效能研究

利用青海省6套YRY-4分量钻孔应变仪2007—2015年的观测资料,将该地区符合扫描范围的地震从震前异常和同震特征两方面进行研究。结果显示:湟源、德令哈分量钻孔应变差应变曲线地震前大多有短期超差异常;分量钻孔应变仪的同震响应幅度与震级、震中距都有关。同一地震,多台仪器多数情况同震响应幅度与震中距成反比,少数成正比;一般单台仪器同震响应幅度与地震震级成正比关系,震级越大同震响应幅度越大;分量钻孔应变仪的同震响应延迟时间大多与地震震中距成正比,震中距越远同震响应延迟时间越长;分量钻孔应变仪同震响应持续时间与震级基本成正比,震级越大同震持续时间越长。     

非对称交通荷载作用下拓宽路堤动力特性分析

针对山西省境内长期承受非对称交通荷载的公路拓宽路堤,采用FLAC~(3D)建立数值模型,土工格栅采用FLAC~(3D)内置土工格栅单元(geogrid)模拟,其余部分均采用实体单元,屈服准则采用Mohr-Coulomb准则。将交通荷载简化为半正弦波荷载,分析非对称交通荷载作用下不加筋和加筋两种工况下拓宽路堤的变形特性及稳定性,进而改变拓宽路堤部分填土参数、交通荷载幅值、频率和行车间隔等参数,分析其对加筋工况下拓宽路堤变形的影响。结果表明:非对称交通荷载作用下,设置土工格栅加筋对新、旧路堤变形的约束作用有限,但能提高路堤的整体稳定性;增大拓宽路堤填土的压缩模量和黏聚力,可减小新、旧路堤沉降差;增大交通荷载一侧幅值会引起新、旧路堤过大差异沉降;增大交通荷载频率和时间间隔,路堤沉降均逐渐减小,但沉降差保持不变。上述结论对受非对称交通荷载拓宽路堤的施工提供了一定的理论依据。     

滇西南普洱强震群地区地壳形变的数值模拟

滇西南普洱一带地质构造复杂,中-强地震成群活动特征明显,地壳的形变特征与形变机制引起了地学界的广泛关注和深入研究。在参考、借鉴以往研究成果的基础上,本文构建了普洱一带包含活动断裂的二维板有限元模型,以GPS测量得到的块体年运动量作为模型区域的边界约束,模拟计算获得了普洱地区的构造形变空间分布,以NEE、NNW 2个方向、从数值模拟角度对普洱地区的水平形变特征和区域地壳垂直形变场进行了分析和探讨。结果表明:在青藏高原东南缘扩展、高原物质重力滑塌型南东向移动的动力学背景下,研究区内NEE向断裂的活动带动牵引NNW向断裂共轭运动,隆升性质的垂直形变场与60年的大区域水准测量结果相吻合,沿NNW向形变场的分布无规律,应是区域应力累积和震后调整双重作用的结果。沿NEE向形变场呈现了较明显的西部大于东部的分布图像,特别是西北部高值区对应了2014年景谷6.6级强震,最后对研究区的区域动力学问题进行了初步探讨。     

基于DEM与GACOS的InSAR同震形变场大气误差校正北大核心CSCD

从全球地震频发地区选取多次地震事件,以精河地震为例研究基于DEM进行大气误差校正时拟合区选取方法;然后分别基于DEM和GACOS数据对同震形变场进行大气相位延迟改正以分析其校正精度及适用性。结果表明,扣除主要同震形变区域后的相位-高程相关系数大于0.4时,必须对获取的形变场进行大气误差校正,校正后噪声可下降约1~4 cm;相关系数为0.4~0.8时,可通过两种方法相互验证以校正精度;相关系数大于0.8时,可以只使用DEM拟合大气误差分布函数进行校正。基于GACOS进行大气误差校正具有普适性,用于大气噪声较为严重且与地形不相关的平原地区可取得较好效果。