工业开采诱发地震（二）:监测技术和危险性研究

随着页岩气和地热等能源开采过程中可能诱发地震并造成灾害等问题的关注度的提高,及时总结分析国际上已经实施开展的针对可能的诱发地震的监测、危险性分析、风险评价和风险管理工作,对有针对性地预防和减轻此类地震灾害、实现有效的社会治理等均具有重要意义。本文重点对国际上公开发表的学术出版物进行了调研,对目前已有的针对可能的诱发地震的监测系统建设、地震危险性分析和风险评价、风险管理等方面的研究和工作进行了归纳,以期为诱发地震减灾工作提供参考。      

1．由采矿诱发的微震活动性综述

本文全面介绍了采矿诱发微震的研究进展。其中包括监测系统的改进、诱发微震机理的认识以及进行预测和防治的可能途径，在采矿诱发微震的研究中，全面引入了天然地震的研究方法即地球物理方法。该文对各国采矿业引进地球物理方法的情况进行了较全面的总结。     

油气田典型岩石三轴压缩变形破坏与声发射活动特征——四川盆地震旦系白云岩及页岩的破坏过程

随着二氧化碳地质封存、深部地热开采、地下储气库建设、页岩气开发、二次驱油/驱气等工业应用的快速发展,与地下流体注入有关的诱发地震活动呈现一定的增加趋势.利用声发射实验观测油气田典型岩石在三轴压缩条件下变形破坏过程与声发射活动特征,对研究注水诱发地震过程有着重要意义.本文利用四川盆地现场采集的震旦系白云岩及页岩,采用实验室声发射技术观测研究岩石三轴压缩变形破坏过程中地震波速度等物性参数及声发射事件时空分布特征.实验结果表明:震旦系白云岩及页岩在变形破坏过程中均有一定的声发射活动.根据声发射定位结果,声发射主要集中在破坏前后的较短时间内,页岩的层理面为结构弱面,控制最终破坏面的形态及声发射特征.根据应力-应变结果,白云岩在压缩的后期阶段有一定的扩容现象,但页岩在整个压缩阶段均没有明显扩容现象.研究结果表明四川盆地较古老的白云岩及页岩具有脆性破坏特征,地下流体注入容易诱发微震活动,形成裂缝,有利于页岩气压裂开采.微震活动有利于监测裂缝的发生发展,但同时在页岩气开发及二氧化碳地质封存时应采取相应的预防控制措施进行安全合理的储盖层管理,避免灾害性诱发地震的发生.     

基于微震特性的断层检测技术（英文）

对非常规油气藏,断层既可以成为油气的流通通道,也可能成为油气藏开采开发的阻碍,体现在(1)导致压裂液的滤失;(2)导致储层水淹;(3)诱发小型地震。因地震勘探分辨率的影响使得部分小型断层无法被有效检测,该类断层在压裂施工过程中变得异常活跃并释放出大量的微震。为此,本文总结出一种融合微震时空特征、相对震级、震源机制、振幅、频率的天然断层识别方法。该方法基于储层力学机理分析天然断层和压裂裂缝激发的力学环境,并得出其时空分布规律;通过引入微地震相对震级的算法对天然断层和压裂裂缝活动所致的微地震事件进行标定,并基于地震位移理论分析天然断层和压裂裂缝所致微震的动力学特征,得出其在频率和振幅存在的差异。通过微地震地面和井中监测实例的应用和验证,该方法能有效地达到对天然断层和压裂裂缝识别的目的。     

微地震及其监测综述——走向基于低信噪比的微破裂向量扫描

微地震是岩石的微小破裂.微地震的另一个重要特性是剪切破裂或具有很强的剪切破裂成分.通常人们感兴趣的是监测与生产生活密切相关的微震活动，为环保、安全、提高生产效率、以及一般地学科研提供参数和建议.观测微震信号，以及对其实施的数理、地质、工程等的分析研究，构成整个微震监测系统.对此系统的每一步骤，从观测仪器研制、微震台网布设、微震记录的整理和去噪、微震或其释放能量分布的定位，到分析微震时空活动规律，以及这些规律与监测目标之间关联的解释，都必须从上述微震的两个特性出发.微震监测照搬常用勘探地震学和一般小震以上的天然地震学软硬件是不恰当的．微震监测方法的研发必须严格服从地震学基本原理并进行大量实验．本文对微震及其监测进行了一般综述，说明了由于微震的两个重要特性及其监测的艰难程度，也由于微震监测成为伴随生产生活的性价比较高的常规手段的需求，而不得不研发基于微小信噪比数据记录、实施地面监测的微破裂向量扫描技术，较详细地描述了其原理、微震仪器、台网布设原则、去噪、分析解释原则、和应用中所得到的重要分析结论，以及目前存在的技术问题和展望．     

水口水库诱发地震的微震前兆信息与趋势预测

福建水口水库地震是我国当前正在发生的一个大型水库诱发地震实例。针对水库地震序列中普遍含有大量微震的特点,探讨微震活动可能包含的前兆信息。研究发现,“微震相对频度”在水口水库地震趋势预测中具有明显的前兆性质,文中还介绍了“微震相对频度”作为一种前兆指标在该水库地震趋势预测实践中的应用效果,对“微震相对频度”的物理意义以及深入开展“微地震研究”的前景进行了讨论。     

清江隔河岩水库区地壳形变与诱发地震的可能性

隔河岩水库蓄水前即开始对穿越库区的主要断裂进行监测，并设立了地震观测台网，蓄水后库尾区诱发了一系列微震，形成几次水库诱发地震高潮期。本文通过库区近4年的形变观测资料的初步分析，论述了蓄水后库区地壳的稳定性及诱发地震与断层活动的关系，探讨了今后诱发较大地震的可能性。     

隔河岩水库诱发地震的环境条件

隔河岩水库蓄水后相继发生地震１０００余次,共中最大震级ＭＬ＝３．３。微震活动与水库蓄水过程密切相关,属水库诱发地震。库水渗透、地下水储积、岩溶和现代应力场等因素的研究表明,水库蓄水使库区水文地质环境发生变化,从而诱发了一系列微震。     

清江隔河岩水库区地壳表变与诱发地震的可能性

隔河岩水库蓄水前即开始地穿越库区的主要断裂进行监测，并设立了地震观测台网，蓄水后库尾区诱发一系列微震，形成几次水库诱发地震高潮期，本文通过库区近４年的形变观测资料的初步分析，论述了蓄水后库区地壳的稳定性及诱发地震与断层活动的关系，探讨了今后诱发较大地震的可能性。     

2．加拿大由采矿诱发的地震活动性综述

由于区域地震台网布设到开采矿区，加拿大对矿震活动的监测工作已得到了改进。矿震的强度、频度，会随着采矿向更深处发展并随开采率的加速而增加．因为许多矿山（钾盐、煤和金属）的面积范围较大，所以现今监测这些矿震的最可行和最实用的方法是，在发生微震活动的矿内或矿的地表布设地震台网。在少数几个矿山周围已部署了地震台网，并且还计划在近代经历过剧烈矿震的其它矿山周围布设地震台网。本文描述了６次矿震的震源机制，并且介绍了有关的Ｐ波、Ｓ波辐射图像。把实际地震的辐射图像与理论上的预测进行比较，是判断潜在源机制的快速方法，另外，可用识别较大事件前的微震活动图像方法来减轻严重事件所造成的潜在损失。     

基于向量扫描法的微地震震级确定方法

对地震记录中显著可视事件震级的确定,已有如里氏震级、矩震级、不同定义的震级之间的关联、震级与能量之间的关系等成熟方法。然而,由于微地震事件记录常淹没在背景噪声中,无法实施包括确定震级在内的传统定位。为比较不同类型不同地域的微震大小、研究微震机制及诱发原因、使用其安全预警等,我们外延里氏震级到微震范畴,定义了等效里氏微震震级：根据微破裂向量扫描输出的无量纲能量或最小信噪比,估计一定时空中单位时间单位台站所接收的在时空目标一点上的等效能量和震级。文中列出了目前我们在微震监测中发现的几类微震的大小规模。     

Study on the relationship between geothermal exploitation and seismic activity in Xi’an region

Based on the analysis of the induced earthquakes in China and abroad, we get some ideas about earthquakes induced by pumping water out of a well or injecting water into a well. The induced earthquakes usually occur near the well, and they are generally small earthquakes. The earthquake sources are shallow, and they belong to the main shock-after shock type of earthquake or the swarm-type of earthquake. The magnitude and the quantity of the induced earthquakes obviously depend on the pressure and the quantity of water pumped or injected. These earthquakes happen as soon as pumping or injecting occurrence, or after ten or twenty days, they may occur at the time of injecting mud or injecting high pressure water when a well is being drilled, or at the time when the ground water is being normally exploited. A large quantity of hot water has been exploited since 1990 in Xi’an, and the quantity of water exploited has been increasing year by year, as a result the groundwater level has been dropping with the water pumped out and the water level is high in summer and low in winter. The earthquakes in Xi’an region belong to the solitary-type and they spread outside Xi’an city where the wells are concentrated but no earthquake happens. The seismic frequency and the energy released have no relation with the quantity of water exploitation or the water level in the well. It is considered that geothermal exploitation does not induce earthquakes in and around Xi’an because of its specially geological condition. Foundation item: Project sponsored by the Landslide Office of Shaanxi Province and Society of Disaster Reduction of Shaanxi Province.     

基于微震监测的页岩气开采区b值特征研究

四川盆地南部的长宁页岩气开发区附近地震频发,近年来已发生近10次ML＞4.0的中型地震和万余次ML1.0～3.0的小微地震,灾害风险持续增高.由于国家地震台网的固定台站较为分散,难以捕捉到1级以下微震事件的精确信息,通过近场微震监测数据来分析页岩气开发区的地震风险演化趋势,已经成为势在必行的科学问题.本文基于专门布设的...     

Study on the relationship between geothermal exploitation and seismic activity in Xi''''an region

IntroductionGeothermal energy is a new and clear energy resource. It is very useful in heating and generating electricity and medical treating. The Assembly of International Environmental Protection in 1992 predicted that the usage and development of geothermal energy would exceed the traditional energy such as oil and coal, and its developmental prospect will be very bright.There are great geothermal resources in Weihe basin. The average value of heat flow in Weihe basin is 7.88(10(2 W/m2…     

Study on the relationship between geothermal exploitation and seismic activity in Xi＇an region

Based on the analysis of the induced earthquakes in China and abroad, we get some ideas about earthquakes induced by pumping water out of a well or injecting water into a well. The induced earthquakes usually occur near the well, and they are generally small earthquakes. The earthquake sources are shallow, and they belong to the main shock-after shock type of earthquake or the swarm-type of earthquake. The magnitude and the quantity of the induced earthquakes obviously depend on the pressure and the quantity of water pumped or injected. These earthquakes happen as soon as pumping or injecting occurrence, or after ten or twenty days, they may occur at the time of injecting mud or injecting high pressure water when a well is being drilled, or at the time when the ground water is being normally exploited. A large quantity of hot water has been exploited since 1990 in Xi＇an, and the quantity of water exploited has been increasing year by year, as a result the groundwater level has been dropping with the water pumped out and the water level is high in summer and low in winter. The earthquakes in Xi＇an region belong to the solitary-type and they spread outside Xi＇an city where the wells are concentrated but no earthquake happens.The seismic frequency and the energy released have no relation with the quantity of water exploitation or the water level in the well. It is considered that geothermal exploitation does not induce earthquakes in and around Xi＇an because of its specially geological condition.     

Passive Seismic Monitoring of Mine-scale Geothermal Activity: A Trial at Lihir Open Pit Mine

The Lihir open pit mine in Papua New Guinea is located inside an old volcano where geothermal activity is strongly present. Outbursts of hot water and steam into the mining areas were a major safety concern. Passive seismic monitoring was carried out at the mine to investigate whether the geothermal activities could be detected and located using microseismic techniques in a mining environment. In this trial, sixteen triaxial geophones which can withstand temperature up to 200°C were used and installed in four deep boreholes inside the pit. The microseismic events were discriminated using the STA/LTA triggering criterion. During 6 weeks of monitoring, more than 17,000 events were recorded. Approximately 12% of the events showed harmonic vibration characteristics similar to those observed in other geothermal and volcanic areas, suggesting that the geothermal activity inside the pit was captured by the microseismic monitoring system. More than 75% of the events present both P and S waves and they were interpreted to be associated with rock fracturing due to stress release near the bottom of the pit. Many geothermal-type events were located in areas where shear events occurred, implying that the detected geothermal events were not far from the mining area below the pit and they may also be associated with mining. The borehole installation of the geophones significantly reduced the interference of mining noise and achieved good observation of the seismic events. However, equipment installation requires great attention as the geophones may be destroyed due to unexpected rising temperature within the boreholes.     

Some results of microseismic monitoring in the Elbrus Region

The results of microseismic monitoring in the adit of the neutrino laboratory (Institute of Nuclear Research, Russian Academy of Sciences) in the Elbrus Region are presented. Three-component computer recording was carried out in the frequency band 10–120 Hz with 5-second averaging of the amplitudes of vibrations. We consider the results of processing the data yielded by the monitoring in the adit during nine months since March 2008. The seismic field at the observation point is composed of three main contributions: the local earthquakes associated with two main fluid-magmatic sources, which are located nearby the adit; a slowly varying wave field, which is probably related to the same sources; and the industrial noise, namely, the vibrations caused by the traffic of carriages and a weak stationary background noise.     

Main Factors Affecting the Distribution of the Macroscopic Destruction Field of Earthquake

It is proposed that some possible macroseismic epicenters can be determined quickly from the relationship that the microseismic epicenters located by instruments bear with faults.Based on these so-called macroseismic epicenters,we can make fast seismic hazard estimation after a shock by use of the empirical distribution model of seismic intensity.In comparison with the method that uses the microseismic epicenters directly,this approach can increase the preccision of fast seismic hazard estimation.Statistical analysis of 133 main earthquakes in China was made.The result shows that the deviation distance between the microseismic epicenter and macroseismic epicenter falls within the range of 35km for 88% earthquakes of the total and within the range of 35to 75km for the remaining ones.Then,we can take the area that has the microseismic epicenter as its center and is 35km in radius as the area for emphatic analysis,and take the area within 75km around the microseismic epicenter as the area for general analysis.The relation between the 66 earthquake cases on the N-S Seismic Belt in China and the spatial distribution characteristics of faults and the results of focal mechanism solution were analyzed in detail.We know from the analysis that the error of instrumental epicenter determination is not the only factor that gives effects to the deviation of the macroseismic epicenter.In addiditon to it,the fault size,fault distribution,fault activity,fault intersection types,earthquake magnitude,etc,are also main affecting factors.By sorting out ,processing and analyzing these affecting factors,the principle and procedures for quickly determining the possible position of the macroseismic epicenter were set up.Taking these as a basis and establishing a nationwide database of faults that contains relevant factors,it is possible to apply this method in practical fast estimation of seismic hazard.     

Induced earthquakes in the development of unconventional energy resources

It has long been known that human activities such as waste fluid disposal and reservoir impoundment may cause earthquakes. Recently, anthropogenic activities to tackle the increasing energy demand and to address climate change issues are also reported to induce earthquakes. These activities have a common attribute in that fluids are injected and extracted underground and induce spatiotemporal changes of pore pressure and stress, which may cause slip on faults. Induced earthquakes not only pose significant impacts on seismic hazard assessment and preparation, but also raise the question to the society as how to balance the economic needs of resources development and the public’s concerns about potential environmental impacts. Here we review the observations of fluid-injection/extraction induced earthquakes, ground deformation associated with these activities, and their physical mechanisms. Furthermore, we discuss the influences of induced earthquakes on seismic hazard models, regulatory policies on these anthropogenic activities, and current development of academic, industrial and government initiatives and collaborations in order to understand this intriguing phenomenon and address associated challenges.     

试论地震在泥石流形成中的作用

地震和泥石流是自然界常见的灾种。对地震在泥石流形成中的作用以及地震泥石流的特征进行了初步探讨后认为，强烈地震区和新构造运动活跃区往往也是泥石流高发区；地震通过为泥石流提供固体物质来源、水源、动力条件和激发条件等影响泥石流的形成和发展；地震引发的泥石流具有滞后性、周期性、区域性和多沟同时暴发的特点