在地震观测中,地震数据中普遍包含有噪声信号.由于噪声信号的干扰,地震分析的效率会受到不同程度的影响.传统的去噪方法通常需要噪声的先验知识,并且滤波时会造成部分有效信号丢失.针对这一问题,本文提出一种将自适应噪声完全集合经验模态分解(CEEMDAN)算法与Hurst指数相结合的地震数据去噪方法.首先通过CEEMDAN方法将信号分解为一系列本征模函数(IMF),然后利用Hurst指数对滤波后的IMF分量进行识别,最后对地震数据IMF分量进行重构,从而实现数据去噪.与传统方法的去噪效果对比表明,本文方法可将低信噪比波形的去噪效果提高32％,将高信噪比波形的去噪效果提高6倍.同时对地磁数据的去噪结果表明,本文方法能够较完整地将地铁噪声从地磁信号波形中滤除.

为了探讨桂东北中生代构造演化特征,文章对桂东北姑婆山复式花岗岩体及其闪长质暗色包体进行了详细的岩石学、年代学和地球化学研究.年代学测试结果表明,闪长质暗色包体的形成时代为142±1 Ma,为首次在本区识别出了早白垩世闪长质暗色包体.元素地球化学分析结果显示闪长质暗色包体的SiO2含量为55.66%～56.72%,MgO为2.26%～2.30%,Fe2O3T为10.43%～10.77%;寄主花岗岩样品的SiO2含量为68.33%～68.67%,Fe2O3T为3.73%～3.89%,MgO为0.60%～0.64%,具有较高的10000Ga/Al比值和Zr+Nb+Ce+Y含量,整体表现出A型花岗岩的地球化学特征.寄主岩石和暗色包体均富含大离子亲石元素和高场强元素.综合上述数据,表明闪长质暗色包体是岩浆混合作用的产物,其形成与华南晚中生代岩石圈的伸展减薄作用有关;结合相关区域地质资料,表明华南中生代时期的岩石圈伸展减薄呈幕式发生,从而导致华南发育多期次、多阶段的岩浆作用.

2010年6月28日至8月初,广西凌云与凤山交界地区出现一次罕见的震群活动.利用震区附近8个近距离台站所记录的数字地震波形,按照高信噪比和计算要求,挑选出此次震群中74次ML＞1.5地震可用于计算地震尾波的共179条三分向波形记录,采用Sato单次散射模型经滤波以及消除环境噪声后,计算了地震尾波传播过程途经区的品质因子 Q(f)值;拟合Q(f)值与频率f之间的关系,得到研究区Q(f)=(44.32±23.56)f0.88±017;并对震中区及其邻区地震尾波衰减的时间与空间特征进行了探讨.通过分析震区及其附近尾波衰减参数与尾波采样体之间的关系,认为该区域可能存在浅部高衰减层.此次震群是在低应力水平条件下发生的,震中区Q.值较其他台站高,其地震尾波衰减较慢,介质非均匀性水平相对较低,震中区为低衰减区域,介质较为稳定.

按照高信噪比和计算要求,从2006—2013年广西龙滩水库地震台网的10个子台记录到的龙滩库区近场数字地震波形中挑选出3822条三分向记录,经滤波和消除环境噪声后,采用Sato单次散射模型,计算了地震波传播路径上的尾波Q(f)值,对Q(f)与频率f之间的关系进行了拟合,并在此基础上分析讨论了库区尾波衰减的时空特征.结果显示,龙滩库区总体呈低Q0值和依赖性指数 η 较高的特点,这两个参数值均低于浙江珊溪水库,与其地震活动程度高于后者的事实相一致.尾波Q值的空间分布显示,周围小震密集分布的台站和历史地震活跃地区的台站的Q0值低于相对于周围小震分布稀疏的台站的Q0值.库区尾波衰减参数与尾波采样体之间的关系显示,采样深度越深,尾波参数Q0值越低,因此认为该区域可能存在深部高衰减层.衰减参数随时间的变化过程表明,蓄水后地震尾波衰减参数仍主要反映了库区原有地壳内部介质的非均匀性和地震波吸收特性,库区地壳介质特性无显著变化,但局部敏感点有所调整.

利用天然地震震源和人工爆破震源之间信号能量分布的差异,结合RBF神经网络技术,对2类事件进行分类,具体步骤如下:使用8个带通滤波器对事件波形进行滤波,并划分为4个波形段:P波、P波尾波、S波和S波尾波,分别计算每个滤波器信道和波形段的能量特征值,以所得32个特征参数作为输入向量,利用RBF神经网络,对地震和爆破事件进行分类识别.结果表明,基于RBF神经网络的地震事件识别方法,识别率为88.1％,具有较高的准确性,可作为地震与爆破事件识别的一个重要依据.

文中利用桂西北地区2014-2018年流动重力与2015-2017年GPS观测资料,结合区域地质构造环境和区内发生的南丹Ms4.0地震震例,系统分析了区域重力场变化与地壳水平运动的时空分布特征及其机理,进一步研究和探讨了区域重力场变化、地壳水平形变、地质构造和地震活动的相互关系.结果 表明:1)2017年7月15日南丹Ms4.0地震发生在重力差异变化四象限中心附近,异常区中心位于木伦-东兰-逻楼断裂、河池-南丹断裂与河池-宜州断裂的交会处.差分尺度重力场动态图像较好地反映了南丹地震前后震中附近的重力变化,是一个局部重力异常、四象限分布特征性异常、重力变化梯度带及零值线拐弯区发震及震后反向恢复变化的系统演化过程.同时,综合南丹地震震源机制解、地震动图和地表调查结果分析认为,南丹地震前与走滑型发震断层效应一致的正、负重力变化四象限分布论证了右旋走滑兼具逆冲运动趋势的存在.2)桂西北地区重力场变化空间分布形态与活动断裂密切相关.累积重力变化等值线走向总体上沿南丹-河池断裂、河池-宜州断裂分布,断裂带两侧重力变化差异较大,且梯度带影响区域较宽.形变场空间分布总体上存在较明显的横向不均匀性,天峨-南丹-环江一带处于重力变化高梯度带、水平形变面压缩过渡带,且位于河池-宜州断裂、河池-南丹断裂与都安-马山断裂交接处附近,受断块差异运动影响的区域及活动断裂交会部位更易于积累应力.3)桂西北地区重力场的几何形态与地壳水平运动空间分布关系密切,证实了区域内存在物质与能量的交换和动力作用,引起活动断层物质变迁和构造变形,在地表产生相应的重力变化.近期,桂西北地区地壳形变异常分析表明:天峨-南丹-环江一带是重力异常变化梯度带,亦是水平形变面压缩过渡带,同时也是莫霍面等深线显著变化地段、ML3.0地震围空区、异常低6值区.综合分析认为该地区仍存在发生中强地震的危险.

In order to understand and grasp the anisotropic characteristics of crustal media in 12 fixed seismic stations of Longtan Reservoir Digital Telemetry Seismic Network (LRDTSN) from impoundment in October 2006 to July 2013, on the basis of precise positioning of seismic events in Longtan Reservoir, using SAM comprehensive splitting analysis method, which contained correlation function calculation, time delay correction and polarization analysis and test, the effective dominant shear-wave polarization direction and delay time (shear-wave splitting parameters) in 9 fixed stations of LRDTSN were calculated. Analysis showed that under the influence and control of principal compressive stress and regional faults in the South China Block, fast shear-wave polarization directions in stations of LRDTSN had obvious local characteristics. The principal compressive stress directions within the scope of Longtan Reservoir included the dominant polarization directions of NW and NNE. Under the impact of loading and unloading water during impoundment of Longtan Reservoir, the spatial distribution of slow shear-wave normalized delay time was uneven, high in the northwest of dam area and slightly high in the periphery of dam area. Meanwhile, shear-wave splitting parameters in some stations had certain correspondence with the water level of reservoir.

Based on the PingguoM4.5 earthquake damage and seismic characteristics of seismic precursor anomaly analysis.The knowledge of damage characteristics, seismic geology, seismic sequence and seismic precursory data of the region are accumulated. The result has certain guiding signiifcance for earthquake prediction, earthquake emergency prediction work. This earthquake, occurred on F2 fracture of North West Zone in western Guangxi strong earthquake active area, belongs to isolated type earthquake sequence. The fault zone is with sinistral thrust characteristics. The earthquake was felt in large range and with wide spread effect. The intensity of the earthquake in epicenter area isVI+, once again relfecting the disaster characteristics of low magnitude, high intensity and serious damage in Guangxi region. Then from the temporal and spatial distribution of earthquakes, parameter of frequency and total fault area, stress drop before and after the earthquake, significant earthquake characteristics and precursory anomalies, the precursory anomaly characteristics of Pingguo earthquake are studied. The results showed that, before the earthquake, precursory anomalies of seismic activity spatial-temporal image, parameter value of seismology, geomagnetism and water level etc are very remarkable. The occurrence of medium and short term anomalies assorted.

2013年6～7月在广西平果县中铝广西分公司3号排泥库附近出现密集小震群活动.本文搜集本次震群中146次可用于计算尾波的ML＞1.0地震的近距离台站数字地震波形,利用波形高信噪比的尾波时间域信号,采用计算尾波品质因子Qc(f)值的Sato模型,通过滤波及去除环境噪声,计算了地震波传播路径上的尾波Qc(f)值;拟合Qc(f)值与频率f之间的关系,分析了排泥库区域地震波衰减的时空特征.根据信噪比及计算要求,从近场7个台站的记录中挑选出273条三分向记录,计算尾波衰减参数,得到尾波Qc(f)与频率f的关系为:Q(f)=(69.07±40.09)f0.90±0.23.结果表明,本区域为低衰减区域,库区Q值相对较高,地震波衰减较慢,且Q值对频率的依赖性不强,研究区介质非均匀性程度低,介质较为稳定.

对红水河上游龙滩水电站大坝所安装的强震动监测台网技术系统进行了详细阐述,内容包括场地的工程概况、台网布局、仪器性能指标及技术系统、数据的采集分析等情况,为其他大坝强震监测台网设计作参考.

利用广西龙滩数字地震台网记录的2006年9月-2013年7月1284次ML1.0级以上地震波形资料,采用Brune (1970)模型,通过几何扩散校正,介质衰减校正,仪器校正等将速度记录谱归算为震源位移谱,使用遗传算法计算拐角频率及零频极限,然后计算地震矩、应力降等小震震源参数,给出各种参数之间的定标关系.研究表明:地震矩、近震震级、破裂半径、矩震级和拐角频率等之间可以拟合为对数或半对数线性关系.而应力降、视应力降分布都比较零散,与地震矩、震源半径的关系并不明显,随地震矩、震源半径的变化关系比较弱.

使用广西数字地震台网记录的2013年6月-7月广西平果ML1.0-3.0震群162次地震波形资料,采用Brune(1970)模型,通过几何扩散校正、介质衰减校正、仪器校正等,将速度记录谱归算为震源位移谱,利用遗传算法计算拐角频率及零频极限,然后计算地震矩、应力降等小震震源参数,系统分析各参数之间的关系.研究表明:近震震级、地震矩、震源破裂半径、拐角频率、应力降等之间可以拟合为对数或半对数的线性关系;地震应力降、视应力与震源破裂半径没有明显的依赖关系,但与地震矩成正相关关系;与其他地区的同类研究结果基本一致,获得各参数的定标关系相近,尤其是通过最小二乘法拟合应力降与地震矩之间的关系后,与浙江珊溪水库地区的应力降与地震矩之间的关系有很强的一致性;与其他地区的应力降及视应力降相比较,本研究区属于低应力释放地区,但由于此次研究的地震事件时间跨度较短,且时间段比较集中,对该地区的应力释放水平还需跟踪研究.

基于遗传算法对大厂矿区的地震进行重新定位.为验证该方法在大厂矿区的应用效果,首先对已知的5次人工爆破进行定位,得出平均定位水平误差在146m范围内(矿区台网定位水平误差为500m),进而对大厂矿区的81次ML1.0级以上地震进行重新定位,结果表明:大厂矿震主要呈北西向展布,且主要集中在大厂断裂右侧;较大地震均与大厂断裂呈平行状分布,推断其附近可能有隐伏断层存在;大厂矿区地震主要受北西向断层的影响,受北东向断层的影响不大.定位后震源平均深度为2.8km,最大深度6.5km,最小深度1.5km.

In order to know the dynamic response mechanism of reservoir-induced seismicity (RIS), this paper has established In order to know the dynamic response mechanism of reservoir-induced seismicity (RIS), this paper has established the quantitative mathematical model and taken the Longtan reservoir as an example, established a 3D-poreelastic finite element model according to geologic structure, deep velocity structure and digital elevation of the reservoir area, calculated the dynamic changes of pore pressure, effective additional normal stress, shear stress and Coulomb failure stress in the faults and rocks at bottom of the reservoir during the process of reservoir storage impounding. Combined with the characteristics of seismic activity in the temporal and spatial distribution of the reservoir area after impoundment, the relationship between the evolution of RIS in space-time and the process of reservoir water body load-unloading and water infiltration, and their possible mechanism have been discussed. Our study shows that: (1) After impoundment of the reservoir in September 30, 2006, seismic activity level around the Longtan reservoir obviously enhanced, and earthquakes mainly concentrated in 5 flooded deepwater areas, that are Luotuo (Cluster I) Bamao (Cluster II) Lalang (Cluster III), Dam head (Cluster IV) and Buliu River (Cluster V) earthquake clusters. The above areas were also the most obviously increasing areas of Delta CFS during the process of reservoir water body load-unloading and water infiltration, but there were seldom earthquakes in the shadow area of Delta CFS. It indicates that there exists closely relationship between variation of Delta CFS and reservoir seismic activities after the impoundment of the Longtan reservoir. (2) Numerical simulation results show that those faults, which have better permeability and directly hydraulic connection with the reservoir, are the superior channels for additional water head pressure diffusion, through those channels, the affection of additional head pressure diffusion can almost reaches deep into 13 km under the ground, and those strata dominated by carbonate from Sinian to Paleozoic become main layer to receive the head pressure. The above results are consistent with the characteristics that focal depths around the Longtan reservoir have been totally less than 13 km and dominantly distributed in 5 similar to 10 km since impoundment. It indicates that pore pressure reduces the shear strength of rocks and partially offsets the effect of confining pressure, so rock mass at those layer are prone to induce seismicity. (3) Whether it is deep or shallow, there exists the vast majority of time overlaps between the intervals of earthquake occrence frequently and the intervals of Delta CFS rising acceleratedly or in high value stage. This maybe indicate that, being influenced by the rapid increase of external loading rate, rocks and faults at the bottom of the reservoir are more prone to become unstable. Meanwhile, the difference of seismic responding time, frequency and magnitude between the deep and the shallow may be related to inhomogeneity of mechanical properties and permeability in different strata. (4) There exists different physical and mechanical mechanism of RIS in the Longtan reservoir: Cluster I, II, III maybe have something to do with the effect of reservoir body gravity loading, pore pressure diffusing and water infiltration weakening; Cluster IV are mainly controlled by the action of reservoir body gravity loading, and the pore pressure diffusion and water infiltration weakening action does not play a leading role; Cluster V is mainly affected by the pore pressure diffusion and water infiltration weakening effect, the body gravity loading effect maybe hold down the seismicity in a certain extent.

In order to know to what degree can elastic wave velocity be influenced by effective stress changes in rock medium at the bottom of reservoir,and the quantitative relationship between changes of elastic wave velocity,pore pressure and effective stress during the process of reservoir water body load-unloading and water infiltration,pre-works have been done on the geological structures and hydrogeologic conditions in the Zipingpu reservoir,Sichuan Province,and its adjacent areas in detail,and a mathematical model was deduced which could describe rock-mass distortion and stability influenced by liquid seepage in porous rock media during the process of reservoir water body loadunloading and water infiltration. On this basis the paper makes a further study to establish a quantitative mathematical model to describe the relationship between elastic wave velocity and effective stress,and also taking Zipingpu reservoir as an example,calcutates the dynamic changes of pore pressure,additional elastic effective stress,and elastic wave velocity using finite element method. The simulation results show that: the change in incremental value of elastic wave velocity during the process of reservoir water body load-unloading and water infiltration is not obvious,the maximum amplitude is only about ±0. 013km / s,and changes mainly concentrate in local areas above 5km depth under the reservoir bottom. The change in incremental value of elastic wave velocity is associated with changes of additional effective stress,similar to reservoir water-level fluctuation in curve shapes. Incremental value of elastic wave is related to location,depth,and additional effective stress of different observation points. The velocity change of P-wave is greater than S-wave at the same observation point. The time sequence changes of elastic wave velocity obtained by this paper are generally similar to the relative velocity variations of the Zipingpu reservoir region obtained by other scholars using seismic ambient noise method,but the variation range is slightly different.

On the basis of the previous work and collections of the latest information on reservoir-induced seismicity, the spatial distribution and time response characteristics of RIS and its relationships with geological structure environment in the reservoir region had been studied by using the method of statistics, the results show that ① in the spatial distribution, RIS mainly concentrated in the range of 10 km away from the reservoir margin and confined to a particular segment of the reservoir. When a certain condition of geological structure and hydrogeological conditions are met in the reservoir region, the activities of RIS will migrate with the changes of water level during water storage and drainage. ② the time responses of RIS are different from region to region and from reservoir to reservoir. In general, RIS’s initial response is dominant when the reservoir is filled less than 1 year, while most of the main earthquakes of RIS occur in more than 1 year after the reservoir initial storage. The “mixture response” is the main form of RIS activities for the long process of reservoir storage, while the“rapid response” and “delayed response” are only a periodic phenomenon. ③RIS response has very complex and diverse relationships with the reservoir water level changes, which can be positive correlation or negative correlation, and higher magnitude of RIS shows certain dependence on the rate of water level changes. ④ RIS spatial and temporal distribution is controlled by the existing internal causes including local terrain features, geological structure, lithologic and hydrogeological conditions in the reservoir area. In fact, all these causes that influenc the spatial and temporal distribution of RIS are interdependent and dialectical united and can not be completely separated.

This paper briefly reviews the development process of the seismic underground network in Guangxi,emphatically analyses the data quality of seismic underground fluid in Guangxi,including stability and continuity,dynamic characteristics,influencing factors and the capacity of information reflection;the paper also analyses the problems of the seismic underground network in Guangxi and puts forward some measures and suggestions for improvement.

龙滩水库2006年10月蓄水以来,库区地震活动频繁,这可能是原有构造地震的进一步活动,也可能是水库诱发地震.因此,有必要对龙滩水库蓄水后发生的地震性质进行判断.本文根据国内外已发生水库诱发地震震例资料和以往经验,结合龙滩库区具体情况,利用定性判断法和概率统计法对龙滩库区地震性质进行验证和判断,结果认为:龙滩库区蓄水后发生的地震属诱发地震.

龙滩水利枢纽位于广西天峨,是一座典型高坝大库容水库.本文通过对库区及周围的地质构造和蓄水前后地震活动分析,总结了龙滩水库蓄水初期诱发地震的时间、空间和深度分布特征以及蓄水后库区水位变化与地震活动关系,讨论了龙滩库区蓄水初期诱发地震机理.

In this paper, the digital and analogue data of groundwater level in Guangxi are compared and analyzed from the aspects of solid tide, seismic water level fluctuation, correlation and inherence quality. The results show that their dynamic variations are similar and a good correlation is found between parallel observations using digital and analogue instruments when the instruments operate well and no failure occurs ( the correlation coefficient of Ping -1 well at Tiandong is from 0.719 to 0.886 and that of Xishan well at Guiping is from 0.917 to 0.995) . Generally the digital observation contains more messages and its sensitivity is better than the analogue observation. With the improvement of instrument performance, it is feasible to use the digital groundwater level instrument to replace the analogue instrument.