广东新丰江地区地震研究

从水库水位变化与地震活动的关系、地震序列统计、地震活动性等方面探讨了广东新丰江地区的地震特征。地震与水库蓄水变化的研究表明,1965年至今该区地震活动的增强与库水位的上升没有明显的线性关系,并且ML≥4.0级地震65％发生在库水位下降或由下降转为平稳波动的过程中,因此,更应关注水库卸荷阶段的地震活动。对于1970年以来该区记录完整的71次ML3.5级以上地震资料研究显示,主余型、多震型和孤立型地震序列所占比例分别为60％、25％和15％;绝大多数序列最大余震均发生在震后30天内。78％的序列三个月内最大余震发生在震后2天内。94％发生在震后10天内：就主余型序列而言,当主震震级较高时最大余震与主震间时间间隔相对较长,主震震级较低时最大余震与主震间时间间隔相对较短：ML4.O级以上地震活动成丛分布明显。     

中国大陆及周缘地震目录完整性统计分析

地震目录资料是进行地震预测、地震危险性分析、地震活动性研究等地震学研究的基础资料.对地震目录资料的完整性可靠性分析是地震学研究的基础工作之一.近几十年来我国积累的大量的仪器地震记录,历史地震也在不断更新,为地震活动性研究提供了更为丰富的样本,因此有必要对新的地震目录进行完整性分析.本文采用了新的统计方法对我国仪器记录地震目录和历史破坏性地震目录进行了完整性分析.结果表明,对于仪器记录地震目录（M≥3.0）我国东部地区1975年后基本完整,西部地区1980年后基本完整.对于历史地震目录（M≥5.0）,东部地区1500年后基本完整,西部地区1950年后基本完整.考虑到华北地震区历史破坏性地震（M≥4³/₄）活动的时间非平稳性,我们采用突变点分析法研究了华北地震区历史破坏性地震目录的时间特征,得到了华北地震区地震活动周期性变化的突变点位置,并揭示了华北地震区历史破坏性地震目录完整起始时间约为公元1500年前后.     

一九八二年四川地震动态

据四川地震台网目录统计,1982年四川境内共发生M≥3.0级地震50次(见1982年四川M≥3.0级地震目录)。其中3.0～3.9级地震46次,4.0～4.9级地震3次,6级地震1次。 1982年6月16日,虽然发生了甘孜6.0级地震,但地震活动在全省范围内无明显增强的现象,在M≥3.0级地震的次数上,反比1981年减少了50％(1981年M≥3.0级地震为100     

青海省及邻近区域历史地震目录完整性分析探讨

以b值研究为基础,运用多种手段对青海及邻近区域的地震目录的完整性进行了分析研究,大致确定了不同震级下限的完整目录的起始时间,得出如下结果:认为4.7级以上地震的完整起始年为1960年左右,5.0级地震的完整起始年为1950年左右;5.5级以上地震的完整起始年为1925年左右;6级以上地震的完整时段为1917年左右。     

地震活动性分析中余震的删除

介绍了几种删除余震的方法,并从地震断层的角度,提出了一种删除余震的新的震级相关时空窗法．采用这些方法,分别对4个具有不同时空尺度的地震目录删除了余震,并对原始目录及删除余震后的目录作了频度统计和R／S分析结果表明删除余震后,地震时间过程的平稳性明显提高,地震事件的独立性增强但仍存在着一定的非随机因素,主要表现在对地震时问过程的R／S分析中,Haret指数H＞0．5．在此基础上,进一步讨论了删除余震方法及其有效性的检验．     

中国大陆中长期地震活动的群集特征

主要研究中国华北地区和南北地震带中长期地震活动的时间特征。选取华北地区和南北地震带二个地震活动地区1970年以来有仪器记录的完整地震目录。作相关地震删除后对于不同起始震级分别计算不同时-空尺度下观测地震数N_p 与泊松分布下理论地震数n_p 的比值(称为时-空“矩”),结果表明无论华北还是南北地震带,无论起始震级是ML 3. 0或ML 4. 0,所有的地震活动过程都显示群集特征N_p/n_p> 1。地震活动随时间呈指数分布,具有标度不变性,分维数在0. 2～0. 7之间变化。     

极值理论在台湾地区地震趋势预测中的应用

利用陈培善等人对极值理论修改后的极值分布函数模型对1971-01～2012-06台湾地区的地震资料进行统计分析。根据地震活动和地震地质构造特征划分区域、确定边界,单位时间的选取由其地震发生的频度和能量来确定,单位时间内最小与最大地震的确定分别考虑相关区域内台网的监控能力以及删除余震后的实际情况,根据修正后的极值理论统计计算出相应地震的复发周期及在未来一定时间内可能发生相应地震的次数与发震概率,并对有关结果进行模型检验和映震能力分析,同时与利用M-T图及震级与G-R关系获取的M≥7.0级地震的复发周期进行比较。     

886—1981年云南地区M≥4.7地震目录

一、前言 一份尽可能完整、准确的强地震目录是我们研究地震活动性和地震预报以及采取必要的防震抗震措施的重要基础资料。 自1965年以来已对云南地区的破坏性地震进行过比较详细的研究。现在根据云南省地震局新编的《云南历史地震资料年表》、《云南地震目录》、以及《中国地震目录》等有关资料,对云南地区M≥4.7级地震的基本参数:发震时间、震中位置及其精度、震级、震中烈度、震源深度等重新进行分析研究,在此基础上编辑了新的云南地区M≥4.7级地震目录。     

云南地区6级以上强震时间分布特征及其概率预测模型研究

系统分析了云南地区肘≥6.0、M≥6.5和M≥7.0地震的间隔时间分布特征;运用M≥5.0地震目录,基于D-R关系的年发生率和泊松分布模型,构建了云南地区M≥6.0、M≥6.5和M≥7.0地震的概率预测模型;结合间隔时间分布统计特征和概率预测模型,对云南地区M≥6.0、M≥6.5和M≥7.0地震,建立了具有概率水平的三...     

云南地区中强地震余震序列部分统计特征分析

依据1965年以来云南地区记录相对完整的108次5.0级以上地震序列资料,研究云南中强地震余震序列统计特征,探讨序列类型、余震震级、余震分布范围及间隔时间等与主震震级之间的关系。云南地区孤立型、主余型、多震型地震序列分别约占3.7%、63.0%及33.3%。5.0级以上主余型地震序列半年内发生的最大余震震级与主震震级总体呈正相关,但主震震级较低时相对离散。云南地区最大余震与主震距离空间分布具有分级的特点:当5.0≤主震震级M6.5时,最大余震优势分布范围是0~20km;当主震震级M≥6.5时,最大余震优势分布范围是5~40km。在云南地区的主余型地震序列中有68%的最大余震发生在主震后10d内,84%发生在震后30d内,97%发生在震后90d内。多震型序列中第一大震与第二大震发生的时间间隔和震中距的分布规律与主余型地震序列基本一致。     

Declustering of Iran earthquake catalog (1983–2017) using the epidemic-type aftershock sequence (ETAS) model

The main goal of this article is to decluster Iranian plateau seismic catalog by the epidemic-type aftershock sequence (ETAS) model and compare the results with some older methods. For this purpose, Iranian plateau bounded in 24°–42°N and 43°–66°E is subdivided into three major tectonic zones: (1) North of Iran (2) Zagros (3) East of Iran. The extracted earthquake catalog had a total of 6034 earthquakes (Mw?>?4) in the time span 1983–2017. The ETAS model is an accepted stochastic approach for seismic evaluation and declustering earthquake catalogs. However, this model has not yet been used to decluster the seismic catalog of Iran. Until now, traditional methods like the Gardner and Knopoff space–time window method and the Reasenberg link-based method have been used in most studies for declustering Iran earthquake catalog. Finally, the results of declustering by the ETAS model are compared with result of Gardner and Knopoff (Bull Seismol Soc Am 64(5):1363–1367, 1974), Uhrhammer (Earthq Notes 57(1):21, 1986), Gruenthal (pers. comm.) and Reasenberg (Geophys Res 90:5479–5495, 1985) declustering methods. The overall conclusion is difficult, but the results confirm the high ability of the ETAS model for declustering Iranian earthquake catalog. Use of the ETAS model is still in its early steps in Iranian seismological researches, and more parametric studies are needed.     

Comparing seismicity declustering techniques by means of the joint use of Allan Factor and Morisita index

In this paper, we propose to compare different declustering methods on the basis of the time-correlation and the space-clustering of the residual earthquake catalog after the declustering techniques have been applied. To this aim, we applied two point process clustering measures, the Allan Factor and the Morisita Index, for the identification and quantification of temporal correlation and spatial clustering in point processes, respectively. We used our joint space–time approach to study the earthquake space–time point processes of southern California and Switzerland with surrounding area, declustered by using the method of Gardner and Knopoff (with Grünthal and Uhmhammer window) and that of Reasenberg (with different setting parameters). Our results show that the residual declustered catalog is still characterized by time-correlated structures at long timescales; however, the cutoff timescale that is the lowest timescale above which the time-correlation is visible is higher with the Reasenberg method while is smaller with the Gardner and Knopoff method with Grünthal window. The space-clustering analysis performed by means of the Morisita Index suggests that the declustering technique effectively reduces the spatial clustering of the seismicity of Switzerland, but does not change the spatial properties of the residual seismic catalogue of the southern California.     

Comparison of seismicity declustering methods using a probabilistic measure of clustering

We present a new measure of earthquake clustering and explore its use for comparing the performance of three different declustering methods. The advantage of this new clustering measure over existing techniques is that it can be used for non-Poissonian background seismicity and, in particular, to compare the results of declustering algorithms where different background models are used. We use our approach to study inter-event times between successive earthquakes using earthquake catalog data from Japan and southern California. A measure of the extent of clustering is introduced by comparing the inter-event time distributions of the background seismicity to that of the whole observed seismicity. Theoretical aspects of the clustering measure are then discussed with respect to the Poissonian and Weibull models for the background inter-event time distribution. In the case of a Poissonian background, the obtained clustering measure shows a decrease followed by an increase, defining a V-shaped trend, which can be explained by the presence of short- and long-range correlation in the inter-event time series. Three previously proposed declustering methods (i.e., the methods of Gardner and Knopoff, Reasenberg, and Zhuang et al.) are used to obtain an approximation of the residual “background” inter-event time distribution in order to apply our clustering measure to real seismicity. The clustering measure is then estimated for different values of magnitude cutoffs and time periods, taking into account the completeness of each catalog. Plots of the clustering measure are presented as clustering attenuation curves (CACs), showing how the correlation decreases when inter-event times increase. The CACs demonstrate strong clustering at short inter-event time ranges and weak clustering at long time ranges. When the algorithm of Gardner and Knopoff is used, the CACs show strong correlation with a weak background at the short inter-event time ranges. The fit of the CACs using the Poissonian background model is successful at short and intermediate inter-event time ranges, but deviates at long ranges. The observed deviation shows that the residual catalog obtained after declustering remains non-Poissonian at long time ranges. The apparent background fraction can be estimated directly from the CAC fit. The CACs using the algorithms of Reasenberg and Zhuang et al. show a relatively similar behavior, with a time correlation decreasing more rapidly than the CACs of Gardner and Knopoff for shorter time ranges. This study offers a novel approach for the study of different types of clustering produced as a result of various hypotheses used to account for different backgrounds.     

Effects of seismic declustering on seismic hazard assessment: a sensitivity study using the Turkish earthquake catalogue

Earthquakes trigger other earthquakes and build up clusters in space and time that in turn create a bias in seismic catalogues. Therefore, declustering is considered as a prerequisite in seismic studies, particularly for probabilistic seismic hazard analysis, not only to eliminate the bias but also to decouple mainshocks and triggered events. However, a declustering process is not a straightforward task due to the complex nature of earthquake phenomena. There exist several declustering methods that mostly employ subjective rules to distinguish between background seismicity and offsprings. Eventually, the final declustered catalogues usually deviate significantly according to the employed method. This issue is raising some concerns, such as how to select the most suitable declustering algorithm, or to assess how this selection affects seismic hazard assessment. In consequence, the main goal of this paper is to quantify the sensitivity of seismic hazard assessments to different declustering techniques. Accordingly, the recently compiled Turkish earthquake catalogue was declustered by making use of three declustering algorithms. A total of six declustered catalogues, two catalogues per method, one by implementing the default input parameters, and one by altering the free input parameters of the employed methods, were produced. The clusters of selected earthquakes were studied in terms of the spatial–temporal distribution of earthquake sequences. A sensitivity analysis was conducted through the major steps of seismic hazard assessment for Istanbul metropolitan city. The seismicity of Istanbul and surroundings was modeled on the basis of four areal source zones. Comparative studies showed that, while the selected declustering algorithm did not significantly affect the completeness periods of moderate to large size earthquakes, it considerably altered those of small magnitude events (e.g. M_w 4.3–5.2) and consequently the recurrence parameters of the source zones. Depending on the declustering algorithm and input parameters, the activity rate was observed to vary up to a factor of two. The differences in the declustered catalogues obtained from different declustering approaches resulted in considerable variations in seismic hazard estimations. The hazard maps at return periods of 475 and 2475 years indicated that peak ground acceleration values may vary up to 20% at some locations. Moreover, the differences in 5% damped elastic spectral accelerations at T = 0.2 for the return periods of 475 and 2475 years are about 18 and 12%, respectively, on the southern shores of Istanbul where the highest hazard levels are observed.     

华北地区地震目录完全性分析

文中发展了由Ｔｉｎｔｉ ｅｔ ａｌ．（１９８５）提出的一种判断地震目录不完全性的方法。它由三步组成：余震和震群的剔除，相对完全性的识别以及绝对完全性的计算。假定经过剔除余震和震群后理想化（即没有任何地震从目录中遗漏）的地震目录是一个稳态随机泊松过程，而对于实际的目录，通过拟合检验，将目录分成一组时间区段，每个区段是相对完全的，并具有不同的地震发生率。如果目录中至少有一区段被认为是绝对完全的，那么真     

联合概率法在合并相邻台网地震目录中的应用:以2014年鲁甸序列为例

中国目前实行的区域地震台网独立运行机制,使得在相邻不同台网的交界地区可能存在多个版本的地震目录和震相观测报告,影响了地震活动性分析与研究.为此,本文提出了一种基于联合概率的方法,可标明两个或多个相邻台网目录中相同的事件,合并它们的震相数据开展重新定位,并重构不同台网交界地区的统一地震目录.该方法的思路与分析步骤是：首先,计算获得不同台网之间具有最小发震时刻差异的两两地震的时空强差异分布,查找并剔除独立地震,计算事件合并的联合概率;其次,基于联合概率分析合并不同台网的地震目录和震相观测报告,对合并事件进行重新定位和定位误差分析,并基于G-R关系检验重构目录的完整性.本文以2014年鲁甸地震序列为例的初步应用结果显示,震相合并之后的地震定位精度相比之前单个台网的结果,特别是相比四川台网的目录,定位精度提高非常显著,合并后的目录与之前相对完整的云南目录接近,但相比由两个台网目录简单拼凑而成的目录更加准确.此外,研究还发现在目录合并过程中,对于4级以上的中强震,应选择M_S而不是以M_L震级标度;震相合并后被复用台站记录的到时信息可用于检测不同台网间的震相拾取是否存在系统偏差.本文提出的方法使得在相邻不同台网的过渡区形成一个统一且尽可能准确可靠的地震目录成为可能.     

基于喜马拉雅台阵的内蒙古地震监测能力薄弱区拾震能力分析

基于中国地震科学台阵资料及内蒙古、甘肃地震台网资料,采用结合台阵策略的震相拾取深度学习方法APP,开展内蒙古地震监测能力薄弱区——阿拉善右旗拾震能力研究。研究结果显示,APP方法检测到了人工目录中97.8%的地震,地震拾取总数为人工目录地震数的22倍。经tomoDD方法定位后,地震深度分布较符合内蒙古西部的地质构造特征。对震源深度与断裂位置间相关性的初步分析显示,深度随纬度变化中有5条深度“集中条带”与研究区7条断裂的位置相对应,深度随经度变化中有4条深度“集中条带”与研究区7条断裂的位置相对应。分析认为,APP拾取方法在实际地震资料应用中展示出较强的泛化能力,可为增强固定地震台网对于监测能力薄弱地区微震的识别能力,以及优化地震台网布局、提高监测能力薄弱地区的地震监测水平等提供参考。     

Study on the Moment Magnitude of Small and Moderate Earthquakes Located in the Inner Mongolia Region

Based on digital seismic waveform data from Inner Mongolia Digital Seismic Network, the source spectrum parameters of 182 small and moderate earthquakes from January, 2009 to September, 2016 are derived, and the seismic moment M₀ and moment magnitude M_W of the earthquakes are calculated. The M_L-M_W relationship and the relationship between stress drop and magnitude are obtained using the linear regression method. It is clear that incorporating the moment magnitude into the seismic quick report catalog and the official earthquake catalog can enrich earthquake observation report content, thus providing better service for earthquake emergency and earthquake scientific research.     

内蒙古呼和浩特-包头地区地震目录的完整性分析

以内蒙古中部的呼和浩特-包头地区(40°～42°N,108°～114°E)作为研究区域,收集整理2001年1月1日至2010年4月30日ML≥1.0地震作为研究对象,按地震样本数目滑动扫描并计算最小完整性震级Mc,绘制Mc的时序变化曲线.分析认为Mc在时间上的变化主要反映台网监测能力和地震活动规律,但台站布局、地震信噪比和人为因素也会引起Mc的短期或不连续性的变化.同时在Rydelek等提出的2个假设条件下,对呼包地区的地震目录完整性进行了RS检验,其结果与上述扫描计算结果一致,也与根据台网监测能力所得到的震级范围吻合,证明本文的计算结果能够比较真实的反映2001年以来呼包地区地震目录在各时段内的完整性.     

Preliminary analysis of earthquake probability based on the synthetic seismic catalog

The analysis of seismic hazards relies on the statistical analysis of historical seismic data and the instrumental seismic catalog to obtain the regional earthquake recurrence interval and earthquake probability. The accuracy of analysis thus depends strongly on the completeness of the seismic data used. However, available seismic catalogs are too short or incomplete for the reliable analysis of the statistical characteristics of earthquakes. If a long-term synthetic seismic catalog can be generated using a physics-based numerical simulation, and the simulation results match the crustal deformation, seismicity, and other observations,then such a synthetic catalog helps us to further understand the characteristics of seismic activity and analyze the regional seismic hazard. In this paper, taking the northeastern Tibetan Plateau as a case study, we establish a three-dimensional visco-elastoplastic finite-element model to simulate earthquake cycles and the spatiotemporal evolution of earthquakes on the model fault system and obtain a seismic catalog on a time scale of tens of thousands of years. On the basis that the model satisfies the regional geodynamics of the northeastern Tibetan Plateau, we analyze seismicity on the northeastern Tibetan Plateau using the simulated synthetic earthquake catalog. The characteristics of earthquake recurrence at different locations and different magnitudes, and the long-term average probability of earthquake occurrence within the fault system on the northeastern Tibetan plateau are studied. The results are a reference for regional seismic hazard assessment and provide a basis for the physics-based numerical prediction of earthquakes.