2012年2月16日河源M4.8级地震

通过地震序列特征分析初步判断认为,河源ML4.8级地震与库水位变化的对应关系不明显,短期内震中区发生更大地震的可能性很小。现场宏观调查结果显示,极震区Ⅵ度等震线长轴为北北西向,震源机制解所反映的震源应力场主压应力方向为北西西向,与区域构造应力场方向一致;地震的发震构造应为北北西向,但震中区附近并无此组断裂出露地表,因此河源ML4.8级地震的成因,仍然值得深入研究。     

大桥水库4.6级地震前后的库水加卸载响应比变化特征

多年的实测数据表明,大桥水库的坝前水位年变化约40m,库水对库盆的静压变化大约为4×105Pa,比固体潮的作用大2个量级,水库的蓄水和放水是对库区影响最大的加卸载力源。根据加卸载响应比理论(LURR),用库区的地震频次和能量分别研究在大桥水库诱发M_S4.6地震前后加卸载响应比的变化。结果表明:在大桥水库及附近相对较大的范围和水体附近相对较小的范围内,当库水加载过程中发生小震群时,地震频次加卸载响应比Y_n和C_r值显示高值异常,表明研究区岩石处于临近破裂状态,其后发生4.6级水库诱发地震;蓄水前后地震频次库水加卸载响应比Y_n和C_r值的平均值有明显差异;在大桥水库诱发的4.6级地震前,库水加卸载作用导致的地震频次及能量的加卸载响应比在震前存在明显的高值异常,震后异常消失。大桥4.6级震例表明库水加卸载响应比可有效应用于水库诱发地震的监测预报     

皎口水库地震精定位、震源机制及发震机理探讨

利用双差定位法对宁波皎口水库2009—2021年地震进行重新定位,通过HASH方法计算了较大地震的震源机制解,基于精确定位后的地震震源位置分布、深度分布以及总体震源机制解特征,结合区域地质构造背景、库区地质条件以及水库水位变化,对发震构造及孕震机理进行探讨。结果表明,皎口水库2009—2012年地震序列与2018—2021年地震序列孕震机理相似,区域性断裂长兴—奉化可能为发震断层;库水通过断裂破碎带下渗,孔隙水压力扩散及库水对岩石的软化弱化长时间作用,造成断层面及其深部某些薄弱部位变为不稳定区域,最后在库水变化导致的加卸荷应力场作用下触发地震。      

青海省河南MS5.1和玛沁MS5.0地震后库玛断裂带的地震活动趋势研究

根据地震活动特征、大武地震台尾波持续时间及长宁、湟源和西宁3个台水氡异常变化，讨论了1999年河南Ms5.1和玛沁Ms5.0地震发生后库玛断裂带的地震活动趋势，结果表明，河南-玛沁地区的中强地震活动与库玛断裂带上的强震活动有明显的对应关系；在库玛断裂带中东段存在一个由ML≥3.0地震围成的空区；上述2次地震发生后大武地震台尾波持续时间异常依然存在，长宁、湟源和西宁台水氡趋势异常仍然持续，据此认为库玛断裂带存在发生强震的背景。     

水诱发地震应力场初步探讨

本文对国内外21个水诱发地震事例的震级—断层破裂长度关系进行回归分析,然后利用断裂力学方法,研究理论震级—断层破裂长度的关系,发现在水库地震的情形里,区域剪应力场的强度水平可以大大小于构造地震的区域剪应力场的强度水平,同时,发现在因库水位下降而触发水库地震的情形里,库水水位的减小量可以小于库水位上升触发地震情形里库水水位的增加量.最后,对注水地震的注水压力进行了讨论。     

地震计的固定

结合实际工作经验,给出一种固定地震计的方法,目的是在地震发生时处于极震区域内的地震计,不至于挪位或翻倒,从而造成极震区地震计停记或记录失真.     

对佛子岭地区1954年以来的地震活动的几点补充

欢迎刘盛武、曹定男同志的不同意见。对佛子岭地区的地震是否属水库地震,我们也并不完全有把握。一则是这个地区在蓄水前也有过地震,地震与蓄水过程的关系,由于缺乏系统的地震资料,不得而知;再则震中距水库也相对较远。我们仅根据蓄水后地震活动相对增高,以及地震与其它水库地震相似,具有极浅源地震的一些客观特征等,暂作为水库地震的一个震例。显然,根据是不够充分的,有必要作进一步的研究和探讨。二、至于水库地震与库水位的相关性,在发震的早期阶段是很明显的,但在后期则不然。如新丰江水库在枯水季节(低库水位时)也发生较强地震。因此,在后期阶段,根据“不相关”似乎也不能得出否定的结论     

对静态应力解发的一种新的统计检验：在1987年苏必斯蒂森山地震序列 …

在过去几年里,许多研究者声称大地震产生的静态应力变化影响后续区域地震活动性的空间和时间分布,地震优先发生在应力增加区,而在应力降低区地震活动性降低。一些研究者提出了定量方法来检验静态应力角发的存在,但还未达成确定一致的认识。我们提出了一套检验静态应力角发的方法,它需要计算大地震发生期间的一组地震事件震源机制节面上的库仓应力变化。我们比较了计算得到的主震之间和之后地震事件震尖机制节面上的库仓应力变２     

青海省河南M_S5.1和玛沁M_S5.0地震后库玛断裂带的地震活动趋势研究

根据地震活动特征、大武地震台尾波持续时间及长宁、湟源和西宁 3个台水氡异常变化 ,讨论了 1 999年河南MS5 .1和玛沁MS5 .0地震发生后库玛断裂带的地震活动趋势 .结果表明 ,河南—玛沁地区的中强地震活动与库玛断裂带上的强震活动有明显的对应关系 ;在库玛断裂带中东段存在一个由ML ≥ 3.0地震围成的空区 ;上述2次地震发生后大武地震台尾波持续时间异常依然存在 ,长宁、湟源和西宁台水氡趋势异常仍然持续 .据此认为库玛断裂带存在发生强震的背景     

弹性多孔介质中应力—孔隙压耦联理论在新丰江水库地震研究中的应用

本文用二维有限元法,将弹性多孔介质中应力-孔隙压耦联理论应用于新丰江水库诱发地震机制的研究。计算中,不仅考虑了均匀、非均匀模型的耦联,还考虑了断层的性质、产状对耦联作用的影响及库水位随时间的变化。 结果表明:附加应力与孔隙压耦联作用是诱发水库地震的重要因素。新丰江水库地震不仅与库区存在的断裂、高密度基底有关,还与库水的加、卸载方式有关。     

广东省汤溪水库大坝抗震稳定性分析

汤溪水库始建于1959年,当时未对地震设防。为响应“国际减灾十年”号召,有关部门要求对该水库大坝的抗震能力进行复核。 在研究区的地震地质、地震活动性以及深部地球物理场等资料的基础上,划分出四个潜在震源区,并用概率地震危险性分析方法,给出复核大坝抗震能力的两个等级的地震动:取地震复发周期475年(相当于地震基本烈度)的峰加速度142.2cm/s~2,复发周期2474年(相当于“罕遇烈度”)的峰加速度229.6cm/s~2。 在上述地震动下,利用三种方法对大坝抗震能力进行复核:1.水工建筑物抗震设计规范SDJ10—78的拟静力法;2.有限元整体永久变形分析法;3.有限滑动永久变形分析法。根据上述三种方法的复核结果,主坝可以抗御地震基本烈度的作用;在罕遇烈度下,几种方法的结果稍有不同;拟静力法的最小安全系数K=1.08,稍小规范规定的1.1;整体永久变形算出的最大水平永久变形10.8cm,估计坝顶和坝坡会出现规模不大条数不多的纵、横向裂缝,因此是可以接受的,有限滑动分析的几种类似的方法给出的结果差别较大,尤其是Romo法,得出水平和垂直最大永久变形分别为66cm和21cm。综合来看,在罕遇烈度下,主坝的抗震能力处于临界状态。副坝抗震能力高,在罕遇烈度下也是令人放心的。     

DETERMINATION OF FAULT PLANE PARAMETERS IN THE LONGTAN RESERVOIR BY USING PRECISELY LOCATED SMALL EARTHQUAKE DATA AND REGIONAL STRESS FIELD

The Longtan reservoir is located in Tian'e County, Guangxi Zhuang Autonomous Region, southwestern China on the upper reaches of Hongshui River, the main stream of the Pearl River. The dam of the reservoir is 200m high, and the maximum water depth can be up to 194m as the water level reaches 400m. The reservoir storage capacity is 27.3 billion cubic meters, so it is a typical high-dam reservoir with large storage capacity. Terrain of the reservoir is high in the west and low in the east. The reservoir is located at the confluence of the Hongshui River, Buliu River, Nanpan River, Beipan River, Mengjiang River and Caodu River. The construction of Longtan hydropower station officially started in July 2001, and the reservoir impoundment was on September 30, 2006. The power station is equipped with 9 sets of 700 000kW water turbine generator units, with a total installed capacity of 6.3 million kW and an average annual generating capacity of 18.7 billion kW·h. So its storage and hydropower capacity rank third only to the world-famous Three Gorges hydropower project and the ultra-large hydropower project in Xiluodu of Jinsha River in China. Seismicity enhanced rapidly in the reservoir area after the impoundment. More the 5 000 earthquakes have been recorded so far, with the maximum magnitude of M_L4.8, which occurred on September 18, 2010. The earthquakes are mainly concentrated in the deep water area where fault zones run through. Assuming the seismogenic fault can be simulated by a plane and most small earthquakes occur nearby the fault plane, the information of seismogenic fault can be obtained by the hypocenter location parameters of small earthquakes.     

澜沧江大朝山水库蓄水前的地震活动本底

分析了大朝山水库蓄水前，水库区域历史中强、强地震背景与1992年来的地震活动格局，及蓄水前9年中库坝区天然地震活动的时、空、强分布，结果表明：大朝山水库区为地震活动水平较低的区域，库坝附近30km以2、3级地震活动为主，库首方向距大坝40km左右的景谷与库尾方向距大坝50km的昌宁、凤庆一带为5级地震活动区，外围100km左右的耿马、澜沧、普洱等地区为6、7级强震活动区；库坝区的地震活动基本符合G—R关系式，b值为0．69，累积应变曲线呈稳定增长趋势，时间分布上出现活跃与平静交替的分布格局。     

四川冕宁大桥水库区水文地质与工程地质条件研究

分析了四川冕宁大桥水库坝区和库区的水地质和工程地质条件,由于库区内断裂比较发育,因此,水库蓄水后,库水将会下渗,易于发生诱发地震,由于大坝和库区位于安宁河断裂中段,因此应注意该段发生诱发地震的可能性,库坝区边坡较稳定,但是近库坝区局部边坡有失稳的可能性,虽然不致于影响水库的正常运行,但是也应引起重视。     

An experimental evaluation of ice cover effects on the dynamic behaviour of a concrete gravity dam

An extensive forced‐vibration testing programme has been carried out on an 84‐m concrete gravity dam located in northeastern Québec, Canada. The dam was subjected to a harmonic load on the crest in summer and severe winter conditions with temperatures ranging from ?10°C to ?15°C and a 1.0–1.5m ice cover. Acceleration and hydrodynamic frequency responses were obtained in different locations on the dam and in the reservoir. The main objective of the repeated tests was to investigate the effects of the ice cover on the dynamic behaviour of the dam–reservoir–foundation system, by comparing summer and winter results. Modifications in damping and resonance frequencies were observed, as well as an additional resonance that was attributed to an interaction of the dam with the ice cover. These findings provided a reliable and unique database for the investigations of dam–reservoir–foundation interaction and, in particular, the ice‐cover effects for dams located in northern regions. Copyright © 2002 John Wiley & Sons, Ltd.     

新丰江水库大坝贯穿裂缝及其稳定性分析

1962年3月19日新丰江水库大坝附近发生M_S 6.1级强烈地震后,13-17#坝段在108.5m高程处出现了长达82m的贯穿裂缝,导致水库渗漏,其后虽进行了加固处理,但经过50多年的运营,贯穿裂缝的现状如何,备受各级政府及专家学者的关注。本文利用近些年大坝上的多次小震观测记录,通过对有无贯穿裂缝坝段的地震加速度时程傅氏谱及上下坝体传递函数的对比分析,对14#坝段的整体性和稳定性进行了系统研究。结果表明,到目前为止,大坝贯穿裂缝没有明显恶化,但整体性依然较差,仍然是大坝稳定性的最大隐患。     

Study of the flood control scheduling scheme for the Three Gorges Reservoir in a catastrophic flood

The Three Gorges Project is the world's largest water conservancy project. According to the design standards for the 1,000‐year flood, flood diversion areas in the Jingjiang reach of the Yangtze River must be utilized to ensure the safety of the Jingjiang area and the city of Wuhan. However, once these areas are used, the economic and life loss in these areas may be very great. Therefore, it is vital to reduce this loss by developing a scheme that reduces the use of the flood diversion areas through flood regulation by the Three Gorges Reservoir (TGR), under the premise of ensuring the safety of the Three Gorges Dam. For a 1,000‐year flood on the basis of a highly destructive flood in 1954, this paper evaluates scheduling schemes in which flood diversion areas are or are not used. The schemes are simulated based on 2.5‐m resolution reservoir topography and an optimized model of dynamic capacity flood regulation. The simulation results show the following. (a) In accord with the normal flood‐control regulation discharge, the maximum water level above the dam should be not more than 175 m, which ensures the safety of the dam and reservoir area. However, it is necessary to utilize the flood diversion areas within the Jingjiang area, and flood discharge can reach 2.81 billion m³. (b) In the case of relying on the TGR to impound floodwaters independently rather than using the flood diversion areas, the maximum water level above the dam reaches 177.35 m, which is less than the flood check level of 180.4 m to ensure the safety of the Three Gorges Dam. The average increase of the TGR water level in the Chongqing area is not more than 0.11 m, which indicates no significant effect on the upstream reservoir area. Comparing the various scheduling schemes, when the flood diversion areas are not used, it is believed that the TGR can execute safe flood control for a 1,000‐year flood, thereby greatly reducing flood damage.     

Evidence for induced seismicity in the vicinity of Fierza reservoir,Northern Albania

The reservoir of Fierza on the Drini River, Northern Albania, is Albania's largest reservoir and it is one of the world's largest reservoirs of high dams (reservoir volume at maximum water level, 2.8 * 10⁹ m³; dam height, 167 m and dam capacity 8 * 10⁶ m³). We compare pre-and postimpounding seismicity of the area surrounding the Fierza reservoir. An increase of seismic microactivity was observed after the impounding of the reservoir. More than 300 microearthquakes, occurred in the immediate vicinity of the main body of the reservoir, with local magnitude ranging between 1.3 and 3.6. A significant change of theb value in the magnitude-frequency relationship was observed. One swarm of microtremors occurred in the northern part of the reservoir on April 4–5, 1981, where an alteration of the tensor of natural tectonic stresses is revealed. The theoretical additional stress and displacement induced by water-load in the bank of the reservoir were estimated for four cross-profiles of the reservoir area and the maximum values resulted near the location of the above swarm.     

四川紫坪铺水库区水文地质与工程地质条件研究

分析了四川紫坪铺水库坝区和库区的水文地质和工程地质条件。由于库区内基岩山区为强烈上升区，地形切割深，高差大，各种不良工程地质现象发育，虽然不致于影响水库的正常工作，但也应引起充分注意。水库畜水后，渗漏问题对水库区和坝区影响较大，应采取相应措施解决；水库蓄水后，库水有可能下渗，应加强对该水库诱发地震的监测和研究。     

浅析使用12位数字强震仪对大坝进行安全监测的可行性

为了论证12位数字强震仪在性能和价格上具有优势，在一个水库大坝内安放了3台12位数字强震仪。期间记录到云南永胜ML6．1级地震和盐源宁蒗ML5．8级地震，结果仪器观测到的谱峰值都在0．80－0．86之间；最大加速度为1．14（伽）。12位数字强震仪能够满足大坝监测要求，而且价格便宜。