Active Depths of Main Faults in the Ying-Qiong Basin Investigated by Multi-Scale Wavelet Decomposition of Bouguer Gravity Anomalies and Power Spectral Methods

The Ying-Qiong Basin is located on the northwestern margin of the South China Sea and at the junction of the South China Block and the Indochina Block.It is characterized by complex geological structures.The existing seismic data in the study area is sparse due to the lack of earthquake activities.Because of the limited source energy and poor coverage of seismic data,the knowledge of deep structures in the area,including the spatial distribution of deep faults,is incomplete.Contrarily,satellite gravity data cover the entire study area and can reveal the spatial distribution of faults.Based on the wavelet multi-scale decomposition method,the Bouguer gravity field in the Ying-Qiong Basin was decomposed and reconstructed to obtain the detailed images of the first-to sixth-order gravitational fields.By incorporating the known geological features,the gravitational field responses of the main faults in the Ying-Qiong Basin were identified in the detailed fields,and the power spectrum analysis yielded the depths of 1.4,8,15,26.5,and 39 km for the average burial depths of the bottom surfaces from the first-to fifth-order detailed fields,respectively.The four main faults in the Yinggehai Basin all have a large active depth range:fault A(No.1)is between 5 and 39 km,fault B is between 26.5 and 39 km,and faults C and D are between 15 and 39 km.However,the depth of active faults in the Qiongdongnan Basin is relatively shallow,mainly between 8 and 26.5 km.

Effect of source parameters on forward-directivity velocity pulse for vertical strike slip fault in half space

It has been found that the large velocity pulse is one of the most important characteristics of near-fault strong ground motions. Some statistical relationships between pulse period and the moment magnitude for near-fault strong ground motions have been established by Somerville （1998）; Alavi and Krawinkler （2000）; and Mavroeidis and Papageorgiou （2003）, where no variety of rupture velocity, fault depth, and fault distance, etc. were considered. Since near-fault ground motions are significantly influenced by the rupture process and source parameters, the effects of some source parameters on the amplitude and the period ofa forward-directivity velocity pulse in a half space are analyzed by the finite difference method combined with the kinematic source model in this paper. The study shows that the rupture velocity, fault depth, position of the initial rupture point and distribution of asperities are the most important parameters to the velocity pulse. Generally, the pulse period decreases and the pulse amplitude increases as the rupture velocity increases for shallow crustal earthquakes. In a definite region besides the fault trace, the pulse period increases as the fault depth increases. For a uniform strike slip fault, rupture initiating from one end of a fault and propagating to the other always generates a higher pulse amplitude and longer pulse period than in other cases.

推覆构造条件下多种因素不同工况边坡稳定性研究

受推覆构造影响,露天矿采区内地层分布错综复杂,不同区域的边坡所处的地质条件各不相同。此外,在推覆作用下,地层的变异性大,难以明确底部地层的具体分布特征,在设计边坡角时,不利于确定安全的边坡角,同时也给露天境界设计带来了极大困难。为了保障资源的高效开发,充分利用地层岩体的稳定边坡角,减少露采剥离量,本文以推覆构造地质条件的刚波夫主矿体露天矿为背景,考虑采深、地下水位及断层上盘平台宽度三种因素,设计不同因素组合,再分别考虑工况条件研究方案,对推覆构造条件复杂地质情况下边坡稳定性进行研究。研究结果表明:在采深单因素工况中,边坡安全系数随采深的增大而降低,且降低速率逐渐变缓;当采深大于210 m后,由于露天采坑为漏斗形,随着深度增加,深部边坡在单位高度上的暴露面积减小,下部边坡的坡体对变形起到抑制作用;在地下水单因素工况和断层上盘平台宽度单因素工况条件下,边坡稳定性随工况条件变差而降低;在双因素或多因素影响下,受到各因素的叠加影响,采深与地下水位高度越大,或断层上盘平台宽度越小时,坡脚及整体的变形量越大;最后,通过对优化后的全采区边坡稳定性进行模拟,当折减系数为1.5时,边坡未出现大范围位移情况,边坡稳定性较好。

Study on the distribution characteristics of faults and their control over petroliferous basins in the China seas and its adjacent areas

As one of the main controlling factors of oil and gas accumulation,faults are closely related to the distribution of oil and gas reservoirs.Studying how faults control petroliferous basins is particularly important.In this work,we investigated the plane positions of major faults in the China seas and its adjacent areas using the normalized vertical derivative of the total horizontal derivative(NVDR-THDR)of the Bouguer gravity anomaly,the fusion results of gravity and magnetic anomalies,and the residual Bouguer gravity anomaly.The apparent depths of major faults in the China seas and its adjacent areas were inverted using the Tilt-Euler method based on the Bouguer gravity anomaly.The results show that the strikes of the faults in the China seas and its adjacent areas are mainly NE and NW,followed by EW,and near-SN.Among them,the lengths of most ultra-crustal faults are in the range of 1000–3000 km,and their apparent depths lie between 10 km and 40 km.The lengths of crustal faults lie between 300 km and 1000 km,and their apparent depths are between 0 km and 20 km.According to the plane positions and apparent depths of the faults,we put forward the concept of fault influence factor for the first time.Based on this factor,the key areas for oil and gas exploration were found as follows:the east of South North China Basin in the intracontinental rift basins;the southeast region of East China Sea Shelf Basin,the Taixinan and Qiongdongnan basins in the continental margin rift basins;Zhongjiannan Basin in the strike-slip pull-apart basins;the Liyue,Beikang,and the Nanweixi basins in the rifted continental basins.This work provides valuable insights into oil and gas exploration,mineral resource exploration,and deep geological structure research in the China seas and its adjacent areas.

Study on System of Faults in the Gulf of Mexico and Adjacent Region based on Gravity Data

In the Gulf of Mexico and adjacent landmasses,faults are very complex,and their distribution is closely related to plate tectonics,ocean-land boundary,and former structure.The plane position of the faults can be identified by the maximum characteristic of the vertical derivative of the normalized vertical derivative of the total horizontal derivative(NVDR-THDR)of the Bouguer gravity anomaly.The apparent depth of the faults is inverted by the Bouguer gravity anomaly curvature property.Based on tectonic evolutionary processes and the plane distribution and apparent depth characteristics of the faults,a complete fault system for the Gulf of Mexico and adjacent areas has been established,including 102 faults.The apparent depths of 33 first-class faults are 16-20 km and for 69 second-class faults are 12-16 km.The F_(1-2)and F_(1-3)subduction fault zones are two caused by the subduction of the Cocos Plate into the old Yucatan and Chorti landmasses;F_(1-11)and F_(1-12)fault zones extend westward to the coast of Guatemala and do not extend into the continent;F_(1-17)and F_(1-20)faults,which control the boundary of the oceanic crust,do not extend southward into the continent.The fault system,which radiates in a"fan-shaped"structure as a whole,unfolds to the northeast.Faults of different nature and sizes are distributed in the Cocos Plate subduction zone,Continental,Gulf of Mexico,Yucatan old landmass and Caribbean Plate in NW,NNW,NS,NE and NEE directions.In the Gulf of Mexico region,the fault system is a comprehensive reflection of former tectonic movements,such as plate movement,drift of old landmasses and expansion of oceanic crusts.The first-class faults control the plate and ocean-continental boundaries.The second-class faults are subordinate to the first-class faults or related to the distribution of different sedimentary layers.

Spatial-temporal characterization of the San Andreas Fault by fault-zone trapped waves at seismic experiment site,Parkfield,California

In this article,we review our previous research for spatial and temporal characterizations of the San Andreas Fault(SAF)at Parkfield,using the fault-zone trapped wave(FZTW)since the middle 1980s.Parkfield,California has been taken as a scientific seismic experimental site in the USA since the 1970s,and the SAF is the target fault to investigate earthquake physics and forecasting.More than ten types of field experiments(including seismic,geophysical,geochemical,geodetic and so on)have been carried out at this experimental site since then.In the fall of 2003,a pair of scientific wells were drilled at the San Andreas Fault Observatory at Depth(SAFOD)site;the main-hole(MH)passed a~200-m-wide low-velocity zone(LVZ)with highly fractured rocks of the SAF at a depth of~3.2 km below the wellhead on the ground level(Hickman et al.,2005;Zoback,2007;Lockner et al.,2011).Borehole seismographs were installed in the SAFOD MH in 2004,which were located within the LVZ of the fault at~3-km depth to probe the internal structure and physical properties of the SAF.On September 282004,a M6 earthquake occurred~15 km southeast of the town of Parkfield.The data recorded in the field experiments before and after the 2004 M6 earthquake provided a unique opportunity to monitor the co-mainshock damage and post-seismic heal of the SAF associated with this strong earthquake.This retrospective review of the results from a sequence of our previous experiments at the Parkfield SAF,California,will be valuable for other researchers who are carrying out seismic experiments at the active faults to develop the community seismic wave velocity models,the fault models and the earthquake forecasting models in global seismogenic regions.

Research on the fault controlling mechanism of geothermal water in Zhangzhou Basin

Fault has an important influence on the storage and movement of geothermal water. The Zhangzhou Basin is wholly located in a granodiorite rock mass. Due to the low permeability of granodiorite, faulted structure has an evident control action on the hydrothermal activity of geothermal fields. Hot springs in Zhangzhou Basin crack along Pingtan-Dongshan Fault to the northeastern direction and emerge along Fu'an-Nanjing Fault. Through measurement of the temperature of several hot springs in the Basin, we found the temperature along the northwestern direction of Zhangzhou-Tianbao Fault is high and the temperature gap between the two sides of Yangxi-Yuanshan Fault is huge; the estimation of geothermal reservoir temperature of geothermal water through quartz geothermometer indicates that the geothermal reservoir temperature of the northern area of Nanjing-Xiamen Fault is obviously higher than that of southern area. Such result indicates that Fault obviously obstructs underground heat source. Under the condition that the average geothermal gradient of the Zhangzhou Basin is set, the circulation depth of the geothermal water of the Zhangzhou Basin measured by geothermal reservoir temperature is 3 550-5 200 m and the circulation depth of the geothermal water of the north of Nanjing-Xiamen Fault is deeper than that of the South.

宝坻-苗庄凸起新生断裂脆韧性转换深度研究

现今地震是最新构造活动的最直接表现,是认识大陆内部非刚性变形特征的最有力工具。尤其是对晚更新世以来开始活动的新生断裂来说,由于发育成熟度低,几何构造上贯通性差且不同区段走向/不同深度倾向差异明显,地震能够揭示其三维空间的变化,尤其是脆韧性转换深度特征,促进对新生活动断裂孕育、发震过程的认识。渤海湾盆地新生走滑活动断裂曾多次发生强震,如唐山M_(S)7.8、三次宁河M_(S)≥6.2地震,这些地震揭示的地壳脆-韧性转换深度对认识该地区地震发震机理和活动性具有重要的现实意义。本文以渤海湾盆地内宝坻-苗庄凸起新生断裂为目标断裂,以发生于宝坻凸起的2012年宝坻M_(S)4.0、M_(S)3.5地震以及发生于苗庄凸起的1976年宁河M_(S)6.2、M_(S)6.9、1977年宁河M_(S)6.2地震为研究对象,基于首都圈数字地震台网的波形资料,采用CAP方法研究宝坻M_(S)4.0、M_(S)3.5地震震源机制解和震源深度,利用近震转换波Sp精确确定震源深度,采用双差方法定位两个地震序列的震源位置,并结合其他资料探讨该地区地震的发震机理以及新生断裂脆韧性转换深度。结果显示:(1)宝坻M_(S)4.0、M_(S)3.5地震震源性质与宝坻-苗庄凸起出露地表的已知断裂不尽相符,结合宁河三次MS≥6.2地震震源参数的有关研究成果,推测它们均发震于宝坻-宁河深大断裂;(2)结合震源区电性结构以及流变结构等模型,宝坻-苗庄凸起这五次显著地震揭示出宝坻-宁河深大断裂的脆韧性转换深度为15km左右;(3)结合渤海湾盆地动力演化过程以及深部地球物理探测等相关资料,推测该地区地震活动主要是宝坻-宁河深大断裂与深部流体作用的结果。

2023年甘肃积石山M_(S)6.2地震:一次逆冲为主的浅源强震

基于区域数字地震台网波形数据,在三维空间内利用波形拟合反演方法获得2023年12月18日甘肃积石山M_(S)6.2地震最佳震源机制解,结果表明:节面Ⅰ走向305°,倾角56°,滑动角61°;节面Ⅱ为走向169°,倾角43°,滑动角125°;矩震级M_(W)6.02。最佳拟合的空间精细位置为102.377°E,35.968°N,深度9 km。结果显示,地震破裂沿NW方向扩展。初步推断此次地震的发震断层面为节面Ⅱ,发震断层是拉脊山北缘断裂(积石山东缘断裂),是一次逆冲为主,兼少量走滑分量的浅源强震事件。

MMC-HVDC双极故障条件下自适应限流控制策略

直流断路器(direct current circuit breaker,DCCB)广泛应用于柔直输电系统,其造价与开断电流密切相关。文中从减小断路器开断电流的角度出发,设计适用于半桥型模块化多电平换流器(modular multilevel converter,MMC)的自适应限流控制结构。在分析MMC直流侧短路电流特性的基础上,利用换流站输入阻抗幅值的变化反映其故障深度,定义换流站故障深度系数K f;将K f引入MMC控制结构,使其与桥臂电压参考值关联,提出针对MMC直流侧短路故障的自适应限流控制方法;在PSCAD/EMTDC平台搭建半桥型MMC柔直输电系统模型,模拟直流侧短路故障清除过程,验证限流控制的有效性。仿真结果表明:文中提出的限流控制方法可依据MMC不同故障深度,实现差异化限流控制,减小DCCB开断电流,提升故障清除速度。

不同抽气深度对阿克苏断层氢观测的影响研究

通过在新疆阿克苏断层氢观测点5~105 cm深度进行的5个不同抽气深度实验可以看出,在断层氢观测中不同抽气深度的氢气背景值、日变幅、动态特征等均存在较大差异。由于氢气的扩散具有较强的穿透性和低粘滞性,造成氢气在观测孔内垂直向上具有明显的不均匀分带性;并且因为观测点所处的构造位置差异及气象因素的影响,造成氢气背景值及观测数据质量的差异。在阿克苏观测点的断层上盘80 cm抽气深度,断层氢数据均方差、变异系数等均明显优于其他深度,可以做为阿克苏断层氢观测的优选深度。

某过断层深埋高水头TBM输水隧洞围岩-支护结构响应规律

为了研究过断层深埋高水头敞开式TBM输水隧洞支护结构的响应规律,对不同支护方案下某过断层深埋高水头敞开式TBM隧洞围岩与支护结构的响应规律进行对比分析,选出最合适的支护设计方案。建立TBM隧洞动态开挖-支护精细仿真模型,逐个研究动态开挖-支护中围岩、锚杆、钢拱架、初喷混凝土、二衬的响应规律。结果表明:依次支护管棚、锚杆、钢拱架、固结灌浆、衬砌后,围岩拱顶变形分别降为不支护时的59.4%、32.9%、32.9%、4.1%、3.2%。盾尾离开后各响应突增,增幅逐步减缓且最终趋于稳定,衬砌支护后突降并稳定。锚杆应力分布不均,支护后拱腰处锚杆应力比拱顶增加快,各锚杆应力越靠近洞壁处越大。管棚+锚杆+钢拱架+固结灌浆+初喷+二衬可保证安全,但需固结围岩弹性模量、黏聚力及内摩擦角分别提高1.0、1.0、0.21倍。

基于MTF-ResDSCNN二维图像的故障诊断方法

为了有效捕获旋转机械振动信号中蕴含的故障特征,进而高效地完成故障诊断任务,设计了一种将二维特征图像和轻量化神经网络相结合的故障诊断模型。首先,将采集到的一维振动信号以改进的集成经验模态分解(Modified Ensemble Empirical Mode Decomposition,MEEMD)算法进行分解,得到本征模态函数(Intrinsic Mode Function,IMF)分量,并筛选相应的IMF分量进行求和重构,以增强振动信号的幅值波动,进而使得马尔科夫变迁场(Markov Transition Field,MTF)能够更为有效地表征重构信号中的故障特征;然后,将MTF生成的二维特征图像输入到残差深度可分离卷积神经网络(Residual Depth Separable Convolutional Neural Network,ResDSCNN)模型中,进行特征提取与故障诊断。使用行星齿轮箱故障数据集验证了模型性能。结果表明,该模型对于各类齿轮故障的诊断正确率可达98%以上。

时序InSAR与GNSS联合约束下的亚东-谷露断裂运动特征

亚东-谷露断裂作为青藏高原东南部自新生代以来规模最大、活动性最强的拉张断裂,在青藏高原的构造变形与物质运移等过程中起着重要的调节与转换作用。但由于以往大地测量资料的不足,导致对亚东-谷露断裂整体运动特征的定量化分析较为匮乏。因此,本文收集并处理了亚东-谷露断裂地区2017年10月至2022年4月的哨兵影像数据,并联合GNSS速度场,解决了不同参考系下的形变场融合问题,获取了覆盖整个亚东-谷露断裂的高精度、高分辨率震间地壳形变场。进一步基于弹性微块体模型,精细厘定了亚东-谷露断裂现今活动特征:断裂整体以东倾为主,最佳倾角为68°,现今以拉张运动为主,速率为2~6 mm/a,并由南到北逐渐递增。另外,该断裂中段和北段的闭锁深度约为14 km;但南段可能受到主喜马拉雅逆冲断裂的影响,导致闭锁区域较浅,深度仅为4 km。最后,基于断裂的滑动亏损率与历史地震分布,分析得到断裂北段的地震危险性更高,为区域的地质灾害评估提供了重要参考。

龙门山断裂带晚三叠世大地震的孕震深度和环境的岩石磁学证据

假玄武玻璃可以形成于深部孕震带到近地表的不同深度,确定其形成深度对揭示断裂带力学性质和大地震孕震环境具有重要意义。本文以龙门山映秀-北川断裂带南段八角庙出露的晚三叠世假玄武玻璃及其围岩(碎裂岩和初碎裂岩)为研究对象,通过岩石磁学、显微结构和地球化学测试,探讨了龙门山断裂带晚三叠世大地震的孕震深度和孕震环境。岩石磁学结果表明,假玄武玻璃和碎裂岩中主要磁性矿物是磁铁矿、单斜磁黄铁矿和顺磁性矿物;初碎裂岩中主要磁性矿物是磁铁矿和顺磁性矿物。假玄武玻璃具有高磁化率值特征,其形成的主要原因是顺磁性矿物在同震摩擦热作用下生成了磁铁矿和单斜磁黄铁矿。磁性矿物的转换过程指示了含有硫化物的弱流体作用的还原性的孕震环境。热磁曲线(χ-T)测试结果揭示了初碎裂岩在自然界中经历的最高温度约为275~300℃,根据地温梯度推算初碎裂岩和假玄武玻璃的形成深度为12.8~14.0km。根据孕震深度、假玄武玻璃构特征和地震机制估算,龙门山断裂带孕震深度的正应力σ≤240.2~264.1MPa,剪应力τ≤144.1~158.5MPa。龙门山断裂带在其漫长的演化过程中发生了多次大地震活动,其中在孕震深度(<14km)固结的碎裂岩带内形成的假玄武玻璃比较容易保存在地震断裂带内,并记录了深部较强的应力特征和弱流体作用的还原性环境。

基于改进决策树算法的电能计量装置故障自动化诊断系统

电网中电能计量装置具有周检工作量大、数量多、巡检成本较高、巡检效率较低以及故障定位用时较长等问题,该文提出以改进决策树算法为依据的电能计量装置故障自动化诊断系统。设计相应的电能计量装置在线监测流程,结合数据挖掘以及决策树算法进行算例模型的搭建。经过实验验证,所提系统能够更高效地进行故障诊断,同时其自动化诊断故障的准确率相比人工判读更高。

全光纤微震监测技术在底板突水监测中的应用研究

目前国内的光纤微震监测系统多是基于光学光栅传感技术,而光纤光栅波长解调限制了系统检测频率与灵敏度,且长时间、连续不间断的微震监测成功案例较少。针对上述问题,提出了一种新型全光纤微震监测系统。以潘二煤矿11023工作面回采过程中底板突水监测为工程背景,使用全光纤微震监测系统与ESG微震监测系统进行对比,得出全光纤微震监测系统具有以下优势:记录的波形频谱特征更清晰,表现出高信噪比优势;对扰动深度的监测范围更大,远距离监测效果更好;震源定位结果分布更加合理,更符合工作面实际开采情况。在监测工作面回采全周期内,分析了11023工作面断层异常区底板破坏与微震活动性关系:在断层和煤层变薄异常区附近,微震事件的数量增多、强度增大;工作面初采期间应力集中释放,受采动影响,底板破坏较深;相对大能量事件主要分布在断层异常区的底板,底板破坏深度约为27 m,微震事件在3煤底板60 m以下没有成线或成面聚集的情况,说明裂隙并未扩展,未形成导水通道,工作面安全回采。

广义阈值表示的机加工自动线能量需求跨层模型

为了实现多层次分析的最优设置,提出了一种基于双机广义阈值表示的机加工自动线能量需求跨层模型。首先通过在优化阶段建立机器和系统组织层之间的交互消除了所描述的次优决策。并且将传统的序贯优化方法转化为递归优化方法。另外分析利用了最小能量时间函数,将具有可变功率和处理速率的机器级高分辨率模型与系统级状态模型联系起来。进一步利用一个马尔可夫广义阈值模型,通过指数分布的向下状态来模拟机器的随机行为,并在互操作缓冲区的实际水平上实现控制策略。最后通过一个工业案例验证了提出的方法能够有效降低成本,提升效率。

断裂构造中电阻率与声波波速特征分析及其在探测过程中的联合运用

查明断裂构造的具体位置对于工程场址的选择和稳定性评价具有重要意义。高密度电阻率法和声波测井是广泛运用于探测断裂构造的地球物理方法。高密度电阻率法具有对低阻体敏感且探测范围较大的特点,但高密度电阻率法的分辨率有限,难以准确圈定地质体的边界位置;声波测井具有准确识别地层的特点,但其横向探测范围非常有限。为了克服上述问题,结合2种方法在断裂构造探测中各自的优势以提高圈定地质体的精度,文章首先通过物性试验证明岩石破裂前后电阻率与声波波速变化的相关性,随后用一实例分析断裂构造的电阻率与声波波速特征以及两者在探测过程中的联合运用,最后借助声波测井数据对高密度电阻率法反演结果进行深度校正,得到断裂构造在地下空间的三维分布位置。结果表明:岩石破裂后的电阻率与声波波速较未破裂前均偏低;断裂构造的破碎带在高密度电阻率法反演剖面上以低阻异常区域存在,在声波波速曲线上破碎带区域的波速值会有明显的骤降,2种方法的组合探测模式可为断裂构造具体位置的圈定提供更好的指导。钻探结果验证了借助声波测井数据校正后的高密度电阻率法反演结果比未校正之前更加符合实际地质情况。

断层影响下深井工作面底板破坏深度预测

底板破坏深度的预测是底板突水防治研究中的重要一环。为研究断层影响下深井工作面底板采动破坏深度,基于现场实测数据,运用多元线性回归分析方法,构建了断层影响下深井工作面底板破坏深度预测模型,并检验了模型的准确性。通过现场监测方法,验证了预测模型的合理性。结果表明,与传统的统计公式相比,提出的预测模型相对误差平均值至少降低了25.49%,采用新预测模型预测含断层的工作面底板破坏深度为44.96 m,现场监测底板破坏深度为45.7 m,新预测模型预测值与现场监测基本一致。该预测模型对预测断层影响下深井底板破坏深度和防治底板突水具有一定的实用价值。