Anomalous seismicity prior to rock bursts: Implications for earthquake prediction

Anomalous seismicity changes (increase followed by a decrease) were recorded prior to three moderate rock bursts in the Star mine, Burke, Idaho. In each case, based upon the anomalous seismicity behavior, miners were evacuated or were prohibited from entering active mine stopes that were located in the immediate vicinity of the seismicity buildup prior to the bursts. Analyses of pre- and post-seismic activity are interpreted in terms of, and shown to be consistent with, the inclusion theory of failure. Implications of these observational results for the problem of rock bursts and earthquake prediction are discussed.     

浙江文成-泰顺交界M4.2地震烈度调查与震害特征

2014年9月12日至2014年10月31日,在浙江文成-泰顺交界的珊溪水库区域发生了最大震级M4.2地震。珊溪水库地区曾在2002、2006年分别发生过最大震级为ML3.9、ML4.6的地震序列,受这2次地震作用影响,震区房屋已经遭受了一定程度的破坏。2014年地震现场调查发现,震区震感明显,房屋受损现象较为普遍,震害具有叠加效应,出现了"小震致灾"的现象。另外,在震中附近的一些道路边坡上,地震还引发了规模较小的崩塌、滑坡等地质灾害。     

部分测震学方法转入日常会商的研究

科学地选取了８种可用于地震短期日常会商的测震学定量预报参量，编写了相应的计算程式及分析预报软件包。计算了新疆乌鲁木齐等６个重点监测区的预报参量背景值和异常定量判据指标。根据参量动态曲线与已有强震震例的对应关系，对各预报参量的预报效能、预报高效能区及盲区、异常出现时段参数均作了详细分析。最后简要介绍了最新实际应用中的预报实例。研究结果及研制的相应软件在实际日常会商中具有较强的实用性价值。     

On the physical essence of the b value for AE of rock tests and natural earthquakes in terms of fracture mechanics

The problem of physical essence of theb value forAE of rock tests and natural earthquakes has been a controversial topic during the past two decades. In the present paper the order and energy of each microfracturing of the microcrack system existing in a rock specimen is discussed from the viewpoint of fracture mechanics, then the whole series ofAE and subsequently the value ofb are determined. The order of microfracturing depends on the parametersKei/Kci whereKei is the effective stress intensity factor of thei-th microcrack andKci is the fracture toughness in the site of thei-th crack. The energy of eachAE can be expressed asηi ∫ loili Gids whereG is the energy release rate of microcarck,loi andli are the original and final crack lengths respectively andηi is the emanating efficiency for thei-th crack. If we assume that the distribution density function of microcrack lengthl isp(l)=Bl−v whereB andγ are constants, then the expressionb=3γ/2 can be deduced. Hence, we have come to the conclusion that the value ofb mirrors essentially the “crack-system-configuration” of the material, which means the distribution of the sizes, shapes and orientations of microcracks over space as well as the distribution of the other relevant physical parameters such as fracture toughness, friction coefficient, etc. Our conclusion is somewhat similar in character to Mogi’s. He concluded thet the heterogeneity of the material plays the most important role in determining the value ofb. The term heterogeneity of course covers the idea of “crack-system-configuration, but we think that our view has a little bit deeper insight to the problem than that of Mogi. This subject is supported by Chinese Joint Seismological Science Foundation.     

Earthquake Prediction Research in China

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中国强震前兆地震活动图像机理的三维数值模拟研究

建立了含有母体岩石、硬包体和随机分布的小裂纹的三维有限元模型，计算了包体和各层实体中的应力分布. 利用最高应力破裂准则、释放破裂单元刚度生与死的方法，模拟强震前岩石的破裂和小震的空间分布特征. 结果表明，文中三种模型都显示出强震前在孕震体即包体附近出现了高应力集中单元. 它们是形成小震空区、条带和地震空间丛集图像的基础. 随机裂纹的存在，有利于在孕震体（包体）外的裂纹端部应力集中，先发生小震，形成包围孕震包体的前兆地震活动图像，而包体中的应力逐渐增加，为发生强震提供了条件. 包体的形状和几何位置是影响强震前兆地震活动图像形态的重要因素. 引入材料的黏弹性，导致了其中应力随时间迅速减小和弹性层某些部位应力随时间的增加. 但在本文设定的构造模型框架和介质参数下，下层黏弹性的存在对上层母体的应力随时间的增加影响不大.     

天山地区地震韵律的初步探讨

根据新疆及苏联天山地区的地震目录和古地震研究成果,将整个天山地区的地震韵律划分为地震世、地震亚世、地震期、地震幕、地震阶五级,探讨了各级韵律的特征。估计了我国天山地区未来地震活动趋势。     

利用GIS进行地震滑坡分析

地震滑坡是由地震引发的一种十分严重的震害，它对人类生命财产所造成的损失是巨大的。地震滑坡事件是一个复杂的过程．影响因素多种多样，滑坡的形成机制十分复杂。为正确认识地震滑坡，以1920年宁夏海原大地震为例，利用GIS强大的空间分析功能，多角度、多层次地对地震滑坡的形成、发生、发展机制进行了研究。指出了用GIS技术研究地震烈度等对地震滑坡的影响作用、合理评价和预测某一地区地震滑坡发生的可能性。     

1997年伽师强震群及预报概况

１９９７年１月２１日以来，新疆伽师地区发生了强震群活动，至４月１６日共发生７次６级地震，新疆维吾尔自治区地震局追踪分析了强震群序列和前兆资料，对其中３次６级，３次５级地震公开向社会作出临震预报，取得了明显的社会减灾实效。     

渤海地区地震参数的修定

本文介绍了一种横向不均匀介质中地震参数的修定方法。该方法以渤海及其邻区地壳、上地幔结构的最新成果为基础构造速度模型,集中起可利用的渤海周边地区的山东、河北,北京和辽宁等台网的资料,统一修定了近年来渤海及其邻区598个地震的震源参数。所有地震都给出了震源深度并且讨论了地震定位的精度。文中给出了近年来渤海内M_L≥4.0级的地震震源参数修定结果,讨论了该区震源深度分布的特征。     

1987年9月19日富蕴北5.8级地震

1987年6月19日新疆富蕴县可可托海镇西北发生了Ms=5.8级地震,震中位于喀依尔提河与阿拉散河交汇处,震中烈度为Ⅶ度,等震线长轴方向与可可托海——二台断裂基本一致。震中区人员无伤亡,仅有山石滚落;Ⅵ、Ⅴ度区内的土平房、有不同程度的损坏个别砖平房,楼房出现裂缝。这次地震属于孤立型地震,震前有中短期异常。     

一次地震预测的案例

2001年11月14日昆仑山8.1级地震后, 川滇地区的震情引起了地震学者的普遍关注。 文中详细阐述了针对当时川滇地区的多种地震与地震前兆观测项的观测异常形成的综合预测意见及预测三要素的判定, 并探讨了8.1级地震对这一预测意见的影响及对经验性地震预报的认识。     

潜在震源区地震年平均发生率确定方法的再探讨

应用断裂带地震复发条件概率作为潜在震源区空间概率函数来确定潜在震源区地震的年平均发生率，并运用断层分段的结果，依据其给定震级地震的平均复发间隔，计算出了未来５０年地震复发的条件概率。并以南北天山地震带为例进行了计算。结果表明，该方法是可行的，计算结果是适宜的。     

Review of the Research of the 2011 MW9.0 Tohoku-Oki Earthquake

On March 11, 2011, a M_W9.0 earthquake occurred in the Japan Trench, causing tremendous casualties, and attracting extensive concern. Based on the results of related research, this paper analyzes the observations, phenomena and understandings of the earthquake from varied aspects, and obtains four main conclusions. (1) The earthquake, occurring in the subduction zone in the Japan Trench located in the northwest boundary of the pacific plate has two zones of concentrated coseismic slip at different depths, and the slip in the deep zone is relatively small. Though there have been many M7.0 historical earthquakes, slips in the shallow zone are large, but there have been few historical strong earthquakes. (2) Constrained by GPS data, the study of fault movement shows that fault movement in the Japan Trench has a background of widely distributed stability and locking (the locking zone is equivalent that of coseismic rupture zone). Perturbation occurred after the 2008 M8.0 Hokkaido earthquake, several M7.0 events had after slips larger than the coseismic slip, and two obvious slow slip events were recorded in 2008 and 2011. Eventually, the March 9, 2011 M7.0 foreshock and the March 11, 2011 M_W9.0 mainshock occurred. The pre-earthquake changing of the fault movement in the Japan Trench is quite clear. (3) Traditional precursory observation show no obvious anomaly, possibly due to monitoring reason. Anomaly before earthquake consists of high stress state in focal zone reflected by some seismic activity parameters, short period anomaly in regional ground motion, etc. (4) The analysis of physical property in focal zone aroused more scientific issues, for example, is there obvious difference between physical property in focal zone and its vicinity? Does frictional property of fault determine seismogenic ability and rupture process? Whether pre-earthquake fault movement include pre-slips? Could deep fluid affect fault movement in focal zone? Experience is the best teacher, and authors hope this paper could be a modest spur to induce others in basic research in earthquake forecast and prediction.     

豫北地区地震活动性研究

利用豫北地区1485年至今M≥4.7级地震和1970年以来ML≥3.0级地震资料,采用了地震活动韵律、6级地震的减震效应、P轴方向变化等方法,对豫北地区,特别是聊兰地震带近几年地震活动特点进行了分析,并剖析了其与1983年菏泽6.0级地震震前异常的差异。     

辽宁地区震群序列特征及其分类的研究

本文对1974年以来，在辽宁及其邻近地区发生的20多个震群作了详细的研究？根据这些震群序列时空分布的表象特征，将其分为四种类型：Ⅰ增强型；Ⅱ衰减型；Ⅲ增减型；Ⅳ双丛（峰）型。这一结果，可作为辽宁地区震群性质（前震序列、前兆震群和非前兆震群）判定的参考依据。     

陕西省地震信息发布系统的研发

针对陕西省地震台网中心原有的震情信息发送系统对速报的微震需要通过人工输入,影响发送速度和准确度的现状,通过分析地震定位结果文件,整合现有的多种发布手段,基于Mapxtreme开发出一套地震信息发布系统,可自动读取微震信息及正式速报地震信息,实现快速发布震情的目的。     

1996年3月19日新疆阿图什6.7级地震前震群的时空分布特征

分析了1996年3月19日新疆阿图什6.7级地震前震群活动的时空分布特征。研究主要结果:(1)阿图什6.7级地震前,震群的空间分布在未来大震震中附近集中,同时大致围成一个长轴约119 km和短轴约110 km的椭圆,阿图什6.7级地震落入椭圆靠边部位;(2)震群的时间进程表明,大震之前约4个月震群活动速率加快,标志着中期异常向短期异常的阶段性转折。最后,对所得结果的可能物理机制以及在地震预报中的应用等问题进行了讨论。     

地震的复发周期

本文提出了一个计算某一地震带(区)上地震复发周期的简单公式: T_M=m·10~(bM-a)式中T_M为震级是M的地震周期,m表示在求震级—频度关系式logN=a-bM中的系数a及b时,使用了m年的资料(时间单位也可以采用年、季度、月、旬等等)。 采用上述公式,作者研究了地震预报中的长期、中期及短临预报的问题。一些震例的研究表明:复发周期在地震预报的许多方面具有广泛的实用意义。不失为地震预报中的一个重要指标。     

Magnitude scale structure from filtered broadbandP-wave records

A series of Hokkaido events, recorded by the FBV Broadband Seismograph System at the KHC Seismic Station, is used to study the structure of the earthquake magnitude scale on the basis of maximum velocity amplitudesA _vmax of teleseismicPwaves in different period bands. Amplitude-periodband (APB) diagrams are constructed for each event. According to the shape of the APB diagrams the events investigated can be divided into three types: (a) events with largestA _vmax values in the intermediate period range (periods ofA _vmax from 2.2 to 23 sec), (b) events with largestA _vmax values in the short-period range (periods ofA _vmax from 1 to 2 sec), (c) events exhibiting anomalous APB diagrams. Type (a) events seem to represent the process of wave generation that prevails for shallow earthquakes. Type (b) events approach to explosive-like generation of seismic waves. The nature of the exceptionally occurring type (c) events must be clarified in further investigations. The influence of the type of earthquake on the magnitude values estimated on the basis of standard class A and B (short-period and intermediate-band) seismograms is demonstrated. It appears that for estimating correct values of earthquake magnitudes complementary information on the process of seismic wave generation in the focus is necessary. At teleseismic distances this information can be obtained from either APB diagrams or amplitude spectra ofP waves recorded, e.g., by broadband velocity sensing instruments.