Investigation of microseismic activity sources in Konya and its vicinity, central Turkey

Different types of seismic activity were recorded in Konya, central Turkey, after the installation of broadband stations by the Kandilli Observatory and the Earthquake Research Institute (KOERI) in 2007. Fifty-nine seismic events with duration magnitudes (Md) between 2.2 and 3.5 were recorded by the Konya (KONT) station in 2007 for statistical analysis. In this study, the microseismic activity in the vicinity of Konya was classified by using the maximum peak amplitude ratio (S/P), power ratio, and spectral amplitude ratio of the vertical component of the seismograms; these differences were used as discriminants. The classification was carried out by using a linear discriminant function (LDF) between two different events. In the discrimination analysis between the quarry blast and the earthquakes, three variables were used together to increase the reliability instead of two variables. After adding one variable to the classification functions, the correct classification percentage increased to 98 from 95%. The results of this study indicate that about 10 and 90% of the selected events are earthquakes and quarry blasts, respectively.     

Seismic hazard assessment under complex source size distribution of mining-induced seismicity

It is well-documented that a variety of factors controlling the rockmass fracturing process in mines often results in a complexity of mining event size distribution. In such cases, the estimation of the probability functions of source size parameterizations, with the use of presently known distribution models, brings about an unacceptable and systematic over- or underestimation of the seismic hazard parameters. It is, therefore, recommended that the non-parametric, kernel estimators of the event size distribution functions, be applied to stationary hazard studies in mining seismicity.These data-driven estimators, adapted to seismic source size characterization, accurately fit all kinds of data underlying distributions, regardless of their complexity. Recently, the non-parametric approach to size characterization was supported by a special method of uncertainty analysis based on resampling techniques. At present, it is a fully developed method, which provides point and interval estimates of size distribution functions and related hazard parameters. Two examples of its use in studying mining seismic data are presented and discussed in this paper. The analyzed data sets were recorded in two different copper mines in Poland. The smoothed bootstrap test for multimodality, which is a specialized tool for investigating the shapes of probability densities, provided highly significant proof that in both cases the probability densities of source size parameterization were complex thus implied the superiority of the non-parametric estimation to the classic, model-based approach in the studied cases. The data were then used to construct non-parametric, kernel estimates of the source size cumulative distribution function (CDF), the exceedance probability and the mean return period. Furthermore, confidence intervals for these quantities were also estimated. The intervals for CDF were narrow, showing that the procedures of non-parametric estimation and resampling based uncertainty analysis were precise. Due to the fact that the mean return period is very sensitive to values of the CDF, in particular for larger events sizes, the uncertainty of the return period estimates was not insignificant but remained manageable. The point and interval estimates of source size CDF and hazard parameters so obtained were compared with the respective point estimates achieved from the inappropriate in the case of complex magnitude distributions, model-based approach.     

Prediction of blast fragmentation using multivariate analysis procedures

An extensive multivariate analysis procedure for prediction of blast fragmentation distribution is presented. Several blasts performed in various mines and rock formations in the world are brought together and evaluated. Blast design parameters, the modulus of elasticity, in situ block size are considered to perform multivariate analysis. The hierarchical cluster analysis is used to separate the blasts data into different groups of similarity. Group memberships were checked by the discriminant analysis. The multivariate regression analysis was applied to develop prediction equations for the estimation of the mean particle size of muckpiles. Two different prediction equations were developed based on the rock stiffness. Validation of the proposed equations on various mines is presented and the capability of the prediction equations was compared with one of the most applied fragmentation distribution models appearing in the blasting literature. Prediction capability of the proposed models was found to be strong. Diversity of the blasts data used is one of the most important aspects of the developed models. The models are not complex and suitable for practical use at mines. Copyright © 2010 John Wiley & Sons, Ltd.     

Dynamic Modelling of Fault Slip Induced by Stress Waves due to Stope Production Blasts

Seismic events can take place due to the interaction of stress waves induced by stope production blasts with faults located in close proximity to stopes. The occurrence of such seismic events needs to be controlled to ensure the safety of the mine operators and the underground mine workings. This paper presents the results of a dynamic numerical modelling study of fault slip induced by stress waves resulting from stope production blasts. First, the calibration of a numerical model having a single blast hole is performed using a charge weight scaling law to determine blast pressure and damping coefficient of the rockmass. Subsequently, a numerical model of a typical Canadian metal mine encompassing a fault parallel to a tabular ore deposit is constructed, and the simulation of stope extraction sequence is carried out with static analyses until the fault exhibits slip burst conditions. At that point, the dynamic analysis begins by applying the calibrated blast pressure to the stope wall in the form of velocities generated by the blast holes. It is shown from the results obtained from the dynamic analysis that the stress waves reflected on the fault create a drop of normal stresses acting on the fault, which produces a reduction in shear stresses while resulting in fault slip. The influence of blast sequences on the behaviour of the fault is also examined assuming several types of blast sequences. Comparison of the blast sequence simulation results indicates that performing simultaneous blasts symmetrically induces the same level of seismic events as separate blasts, although seismic energy is more rapidly released when blasts are performed symmetrically. On the other hand when nine blast holes are blasted simultaneously, a large seismic event is induced, compared to the other two blasts. It is concluded that the separate blasts might be employed under the adopted geological conditions. The developed methodology and procedure to arrive at an ideal blast sequence can be applied to other mines where faults are found in the vicinity of stopes.     

Detection of quarry and mine blast contamination in European regional catalogues

The presence of quarry and mine blasts in seismic catalogues is detected using the Wiemer and Baer (Bull Seism Soc Am 90(2):525–530, 2000) algorithm. The procedure is based on the observation that quarry blasts generally take place during daytime hours: the areas with a high ratio of daytime and night-time events are likely to be regions with quarry activity. In the first part of this work we have tested the method, using both a synthetic and a regional catalogue; in the second part the procedure has been applied to some of the European regional catalogues available on line. The comparison between the results obtained and the location of known quarries and mines for the analysed catalogues confirms the reliability of the methodology in identifying mining areas.     

An Engineering Approach to Seismic Risk Management in Hardrock Mines

The problem of mining-induced seismicity in hardrock mines has become significant as underground mines from around the world are pushing production to deeper levels. At many mines, the risk associated with large seismic events and rockburst damage must be managed to ensure the safety of mine workers and minimise production losses. In this paper, an engineering approach to seismic risk management is described. It relies on accepted risk management techniques, which principally include the identification and understanding of hazards from which risk mitigation measures can be developed. This is achieved using simple but effective analysis techniques of high resolution microseismic data.     

Comparison of interpretations of geochemical soil data by some multivariate statistical methods, Key Anacon, N.B., Canada

The nature of the information - and its usefulness - that can be obtained from some of the more common multivariate statistical techniques is illustrated by their application to H and B horizon soils analyzed for 16 variables from the vicinity of the Key Anacon massive sulphide deposit (New Brunswick, Canada) where the geochemical response is erratic and the contrasts low. The theoretical bases of the statistical techniques are given in an appendix.Stepwise linear discriminant functions are employed as a classifying technique on H horizon soils to identify a regional anomaly, and on B horizon soils to derive discriminant scores to define the location of the sulphide zone. R-mode nonlinear mapping (RNLM) indicates that the variables Hg, Cl⁻, and conductance are closely correlated with the organic carbon content; variations in the latter are clearly related to variations in the secondary environment.Q-mode NLM using Pb, Zn, Co, and Ni as variables (identified as good discriminators by stepwise linear discriminant function) identify “outlying” anomalous samples related to the mineralized zones. A principal component biplot (using the same variables employed in the Q-mode NLM) indicates essentially the same samples as being anomalous as the Q-mode NLM. The biplot technique has the added advantage of also indicating which variable(s) is responsible for any particular sample being identified as anomalous.The practical result of the investigation is that the zone of sulphide mineralization defined by drilling and from underground data is confidently identified and defined. A number of geophysical magnetic anomalies over the same stratigraphic horizon has a relatively weak or no geochemical response, although a few locations are defined as second priority targets for follow-up work.     

Prediction of blast-induced air overpressure using support vector machine

Prediction of blast-induced air overpressure (AOP) is very complicated and intricate due to the number of influencing parameters affecting air wave propagation. In this paper, an attempt has been made to predict the blast-induced AOP by support vector machine (SVM) using maximum charge per delay and distance from blast-face to monitoring station of AOP. To investigate the suitability of this approach, SVM predictions are compared with a generalized predictor equation. Seventy-five air blasts were monitored at different locations around three mines. AOP data sets of two limestone mines are taken for the training and testing of the SVM network as well as to determine site constants for generalized equation. The remaining mine data sets are used for the validation and comparison of AOP.     

辽东湾北部地区混合沉积特征及地球物理响应

混合沉积具有碎屑岩类与碳酸盐岩类的双重特征,国内外尚未建立有效的混和沉积储层识别方法.通过对辽东湾北部地区混合沉积发育背景、岩石学特征分析,将混合沉积分为陆源碎屑型、生物成因碳酸盐型、化学沉淀碳酸盐型3种.明确了3种类型混合沉积的发育相带与模式.通过对不同类型的岩石物理参数交会分析认为:生物成因碳酸盐型具有中低-中高纵波速度、低密度、低纵波阻抗特征,化学沉淀碳酸盐型及陆源碎屑型具有中高纵波速度、高密度、高阻抗特征,纵波阻抗与密度是区分不同类型混合沉积的敏感参数;通过地震正演模拟与实际地震资料响应对比,发现辽北地区沙河街组混合沉积地层受到下伏潜山地层低频强能量的屏蔽,创新采用匹配追踪方法对潜山顶面强反射进行压制,并在此基础上进行岩性敏感参数预测,有效地提高了沙河街组混合沉积储层的识别能力.      

Local adaptive parameterization for the history matching of 3D seismic data

Matching seismic data in assisted history matching processes can be a challenging task. One main idea is to bring flexibility in the choice of the parameters to be perturbed, focusing on the information provided by seismic data. Local parameterization techniques such as pilot-point or gradual deformation methods can be introduced, considering their high adaptability. However, the choice of the spatial supports associated to the perturbed parameters is crucial to successfully reduce the seismic mismatch. The information related to seismic data is sometimes considered to initialize such local methods. Recent attempts to define the regions adaptively have been proposed, focusing on the mismatch between simulated and reference seismic data. However, the regions are defined manually for each optimization process. Therefore, we propose to drive the definition of the parameter support by performing an automatic definition of the regions to be perturbed from the residual maps related to the 3D seismic data. Two methods are developed in this paper. The first one consists in clustering the residual map with classification algorithms. The second method proposes to drive the generation of pilot point locations in an adaptive way. Residual maps, after proper normalization, are considered as probability density functions of the pilot point locations. Both procedures lead to a complete adaptive and highly flexible perturbation technique for 3D seismic matching. A synthetic study based on the PUNQ test case is introduced to illustrate the potential of these adaptive strategies.     

Seismic events discrimination by neuro-fuzzy merging of signal and catalogue features

This article presents an original method for the classification of low magnitude seismic events recorded in France by a network of seismometers. Three types of events are discriminated: earthquakes, mining blasts and rock bursts. This method is based on a merging of catalogue measurements and possibly incomplete measurements deduced from several seismic signals related to the event. The merging is performed by a multi-layer neural network. A fuzzy coding is applied to the input characteristics of the neural network. It allows the network to integrate data imperfections during the learning phase. Then, it is possible to process efficiently incomplete data. The results are obtained on a database composed of all the 1,402 seismic events recorded between August 23^rd 1993 and May 30^th 1994. They show that the fuzzy coding and the merging of catalogue features and signal features extracted from several seismometers for each event increase the performance of correct classification to more than 90% even when the database contains missing values. The confusion rate between earthquakes and mining blasts is simultaneously reduced.     

各向异性煤层裂隙流体因子及地震波速度响应

煤层中瓦斯和水的赋存及运移与裂隙的密度、走向、填充物类型等因素密切相关,为了预防和控制矿井突水、瓦斯突出等灾害性事故,进行煤层裂隙的识别和预测研究,对煤矿开采的安全性评价有重要指示作用。基于裂隙等效模型理论,将Schoenberg线性滑动模型与煤层干裂隙（气充填）和饱水裂隙相结合,分析煤层缝隙中流体因子随不同充填物与裂隙弱度参数（裂隙密度、纵横比、体积模量、剪切模量、拉梅系数）的变化特征,并通过对含垂向裂隙的煤储层进行地震波各向异性速度的响应计算。从HTI型煤层理论模型的正演模拟结果可知,模型中裂隙流体因子与裂隙密度和几何形态呈正相关函数关系,而与充填流体体积模量呈负相关。HTI型煤层P波群、相速度对裂隙中的气、水都比较灵敏,SV波群、相速度对干裂隙（气充填）不敏感,SV波群速度对裂隙中的水很灵敏。通过HTI型煤层裂隙流体因子与各向异性速度等参数的响应分析实现煤层裂隙流体预测的可行性,为分析裂隙型煤层地震波传播特征打下基础,为煤层裂隙流体预测提供理论支持。      

淮南矿区高精度三维地震勘探技术应用

淮南矿业集团于2007年首次将全数字高密度三维地震勘探技术引入煤炭领域,并成功推广应用;由于常规三维地震区块受采动塌陷影响,不具备再次施工高密度三维地震的条件,2012年开始,淮南矿业集团对常规三维地震区块的原始采集数据进行二次精细处理、解释。高密度三维地震勘探和三维地震资料二次处理解释都有效提高了地震资料的信噪比和横向、纵向分辨率,达到了高精度三维地震探测的目的。通过煤矿大量揭露资料对比分析:高密度全数字三维地震勘探技术对于识别小断层、查找陷落柱、刻画灰岩地层裂隙等方面效果显著;常规三维地震资料进行二次精细处理、解释能明显改善下部煤层的成像效果。高精度三维地震勘探技术具有广阔的推广应用前景。      

武汉青山“砂山”粒度特征及其成因指示

根据代表性的武汉青山“砂山”的粒度分析探讨“砂山”的成因。结果表明:剖面砂颗粒含量较高,平均达５９％,粗粉砂约２３％,细粉砂约１１％,黏土含量少。粒度参数特征与典型沙丘砂一致,频率分布曲线为双峰,概率累积曲线为两段式,部分层位三段式,跃移质含量高,显示风积成因,Ｃ—Ｍ图及结构参数散点图与河流沉积物差别明显,判别分析结果正负夹杂。综合看来,“砂山”是末次冰期时出露的河流沉积物经风力吹扬、搬运,在长江南岸堆积而 成。     

Earthquakes in Switzerland and surrounding regions during 2009

This report of the Swiss Seismological Service summarizes the seismic activity in Switzerland and surrounding regions during 2009. During this period, 450 earthquakes and 68 quarry blasts were detected and located in the region under consideration. The three strongest events occurred about 15 km NW of Basel in southern Germany (M_L 4.2), near Wildhaus in the Toggenburg (M_L 4.0) and near Bivio in Graubünden (M_L 3.5). Although felt by the population, they were not reported to have caused any damage. With a total of 24 events with M_L ≥ 2.5, the seismic activity in the year 2009 was close to the average over the previous 34 years.     

Assessment of groundwater quality using multivariate statistical techniques in Hashtgerd Plain, Iran

Multivariate statistical techniques, such as cluster analysis (CA), factor analysis (FA), principal component analysis (PCA), and discriminant analysis (DA), were applied for the evaluation of variations and the interpretation of a large complex groundwater quality data set of the Hashtgerd Plain. In view of this, 13 parameters were measured in groundwater of 26 different wells for two periods. Hierarchical CA grouped the 26 sampling sites into two clusters based on the similarity of groundwater quality characteristics. FA based on PCA, was applied to the data sets of the two different groups obtained from CA, and resulted in three and five effective factors explaining 79.56 and 81.57% of the total variance in groundwater quality data sets of the two clusters, respectively. The main factors obtained from FA indicate that the parameters influencing groundwater quality are mainly related to natural (dissolution of soil and rock), point source (domestic wastewater) and non-point source pollution (agriculture and orchard practices) in the sampling sites of Hashtgerd Plain. DA provided an important data reduction as it uses only three parameters, i.e., electrical conductivity (EC), magnesium (Mg²⁺) and pH, affording more than 98% correct assignations, to discriminate between the two clusters of groundwater wells in the plain. Overall, the results of this study present the effectiveness of the combined use of multivariate statistical techniques for interpretation and reduction of a large data set and for identification of sources for effective groundwater quality management.     

Contamination of seismicity catalogs by quarry blasts: An example from İstanbul and its vicinity,northwestern Turkey

Scientists have proposed two fault systems of different ages in the Sea of Marmara: the Thrace-Eski?ehir Fault Zone of Early Miocene–Early Pliocene age and the North Anatolian Fault Zone of Late Pliocene–Recent age. Different seismicity rates and extensions of these faults onto land near ?stanbul have been suggested. One of the reasons for these differences is the contamination of seismicity catalogs by seismic events from quarries operated in ?stanbul and its vicinity, including Gaziosmanpa?a (Cebeci and Kemerburgaz), Çatalca, Ömerli, Gebze, and Hereke.In this study, we investigated waveforms of 179 seismic events (1.8 < Md < 3.0) from the KOERI, NEMC digital database. We determined differences between earthquakes and quarry blasts based on time- and frequency-domain analyses of their seismograms (amplitude peak ratio, power ratio, and spectral amplitude ratio) and used these differences as discriminants. The results of this study indicate that 15% and 85% of the investigated seismic events are earthquakes and quarry blasts, respectively.     

三维地震约束辫状河储层的多点统计建模研究:以委内瑞拉M区块为例

将地震信息引入多点统计地质建模之中,可以提高模型的井间预测功能.首先以委内瑞拉奥里诺科重油带一个辫状河沉积含油区块为例,结合该区辫状河储层的地质特点,利用井震信息结合的多点统计建模方法,研究了波阻抗的相标定、砂体概率生成曲线选定、训练图像分析、井震影响比等方面的技术细节及它们在辫状河储层多点统计建模中的作用.然后结合辫状河储层的沉积学特征,对研究区的心滩、河道、泛滥平原等微相空间分布的建模结果进行了分析.最后对于不同的储层建模结果进行了不确定性分析.研究表明:井震结合的多点统计建模方法,较好地降低了稀井网地区建模结果的不确定性;通过砂岩概率生成曲线,波阻抗数据转化为地震相的空间概率分布.这样就有效地建立起了地震数据与其地质意义的联系;相比仅用测井信息建模,井震结合建模结果对井间微相预测更具合理性,同时预测的河道、心滩的连续性也得到了更好的体现.      

Regional and local factors in attenuation modelling: Hong Kong case study

Seismic attenuation behaviour is controlled by a large number of wave modification mechanisms. The characteristics of some of these mechanisms are specific to a local area, whilst the remainder can be generalised to the entire seismic region. Factors representing these mechanisms are often not resolved. A new attenuation modelling approach is demonstrated in this paper (using Hong Kong as a case study), to evaluate individual regional and local wave modification factors. Shear wave velocity (SWV) information for the four prevalent geological formations found in Hong Kong was first obtained: (a) at shallow depths from instrumented boreholes; (b) at depths of up to 100–200 m from measurements using the Microtremor SPatial Auto-Correlation (SPAC) technique; (c) at depths of up to 1.5 km from the monitoring of quarry blasts; and (d) at depths from 1.5 to 8 km in the hard basement rock layers from results of seismological refraction surveys. The upper-crust amplification factor calculated from the four modelled rock SWV profiles was then combined with predicted attenuation parameters to determine the upper-crust modification factor (filter function) incorporating the local wave modification characteristics associated with Hong Kong geological formations. Such functions may then be combined with the regional attenuation characteristics in that part of the South China region. A seismic attenuation model was developed by combining the upper-crust modification factor with the regional source function of intra-plate earthquakes, based on stochastic simulations. The ground shaking model developed from the presented methodology is supported by the comparison with macro-seismic data of seven historical earthquake events affecting Hong Kong.