Empirical Global Relations Converting M S and m b to Moment Magnitude

The existence of several magnitude scales used by seismological centers all over the world and the compilation of earthquake catalogs by many authors have rendered globally valid relations connecting magnitude scales a necessity. This would allow the creation of a homogeneous global earthquake catalog, a useful tool for earthquake research. Of special interest is the definition of global relations converting different magnitude scales to the most reliable and useful scale of magnitude, the moment magnitude, M _W. In order to accomplish this, a very large sample of data from international seismological sources (ISC, NEIC, HRVD, etc.) has been collected and processed. The magnitude scales tested against M _W are the surface wave magnitude, M _S, the body wave magnitude, m _b, and the local magnitude, M _L. The moment magnitudes adopted have been taken from the CMT solutions of HRVD and USGS. The data set used in this study contains 20,407 earthquakes, which occurred all over the world during the time period 1.1.1976–31.5.2003, for which moment magnitudes are available. It is shown that well-defined relations hold between M _W and m _b and M _S and that these relations can be reliably used for compiling homogeneous, with respect to magnitude, earthquake catalogs.     

Visual Event Screening of Continuous Seismic Data by Supersonograms

We present a new visualization method for human inspection of seismic data called supersonograms, which maximizes the amount of time and stations visible on screen while retaining the possibility to detect short and low-signal to noise ratio (SNR) signals. This visualization approach is integrated into a seismological software suite used in the seismic aftershock monitoring system (SAMS) of Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) on-site inspections (OSI) to detect suspicious events eventually representing aftershocks from an underground nuclear explosion (UNE). During an OSI, huge amounts of continuous waveform data accumulate from up to 50 six-channel mini-arrays covering an inspection area of 1,000 square kilometers. Sought-after events can have magnitude as low as $\hbox{M}_{\rm L}\,{-2.0}$ and duration of just a few seconds, which makes it particularly hard to discover them in large, noisy datasets. Therefore, the data visualization is based on nonlinearly scaled, noise-adapted spectrograms, i.e., sonograms, which help to distinguish weak signal energy from stationary background noise. Four single-trace sonograms per mini-array can be combined into supersonograms, since the array aperture is small and sonograms suppress differences of local site noise, allowing an analyst to check array-wide signal coherence quickly. In this paper, we present the supersonograms and the software on the basis of a dataset from a creeping, inhabited landslide in Austria where the same station layout is used as in an OSI. Detected signals are fracture processes in the sedimentary landslide, i.e., slidequakes, with $\hbox{M}_{\rm L}\,{-0.5} \,\hbox{\,to}\,{-2.5}$ between July 2009 and July 2011. These signals are comparable in magnitude and duration to expected weak UNE aftershocks.     

地震安评中地震活动性的统计区域与b值

本文讨论我国现行地震安全性评价中,地震活动性研究统计区域的选择及b值计算中存在的问题,提出不一定以地震区带作为统计区域的建议。文中同时指出,累计b值的正确概念应该是无震级上限累计b值,应采用迭代回归计算。文中用实际例子说明作者的建议。     

华北地区地震空区的统计分析

对华北地区1970—2017年出现的地震空区采用统一的识别标准进行全时空清理研究, 结果表明, 华北地区M≥5地震前出现空区的比例为36.7%, 且华北地区M_L≥3.0地震空区的持续时间与主震震级存在一定的线性正相关关系, 但长轴尺度、 起始震级与主震震级的线性关系不明显; 报准率为0.76, 虚报率为0.24, 漏报率为0.60, R值为0.32, 高于具有97.5%置信水平的R₀值, 表明地震空区这种预测方法在华北地区具有较好的预报效果。     

Study on Uncertainties of Seismicity Parameters b and v4 in Seismic Statistical Zones

For several seismic statistical zones in North China,the key factors causing uncertainties in the important seismicity parameters b and ν_4 and the features of their uncertainties are discussed in this paper.The magnitude of uncertainty is also analyzed.It can be seen that the key influencing factors are statistical period,methods of processing statistical samples,lower limit magnitude and the annual average occurrence ratio of large earthquakes.The variation ranges of b and ν_4 in the Tancheng-Lujiang zone are as high as 0.2 and 1.4 respectively,which are similar to those in the Fenwei zone.They are much smaller however in the Hebei zone because of its sufficient statistical samples.     

地震统计区地震活动性参数b值及v4不确定性研究

本文结合华北地区几个地震统计区的实例，探讨了地震统计区的重要地震活动性参数b值和v4不确定性的主要影响因素及其特征，并研究分析了其不确定性的大小。结果表明，地震活动性参数的不确定性主要影响因素为样本统计时段、样本处理方法、统计下限震级、高震级年平均发生率等。在郯庐地震统计区，b值变化可达0．2以上，v4的变化可达1．4以上，汾渭地震统计区的不确定性也基本相当，河北平原地震统计区因为地震样本相对丰富，不确定性要小许多。     

16种地震科学期刊载文被引统计分析

依据《中国学术期刊文献评价统计分析系统》（V 1.0）,统计分析了2003~2007年16种地震科学期刊的总被引频次、影响因子、被引半衰期、即年指标、Web即年下载率等被引指标和较高频次被引论文。同时对期刊的现状进行了初步讨论,并提出了一些建议,以期为办刊提供一定的参考。     

雅江—康定5．0、6．0级地震背景分析

对2001年2月14日和23日在四川省雅江－康定相继发生的5．0和6．0级地城的发震背景进行了初步分析，对雅江地震引发的值得研究的问题作了一些探讨，这些分析和探讨对雅江地震发震构造，块体内部中强地震孕育，块体内部中强地震跟踪预测有一定的启示。     

Sources of Error Model and Progress Metrics for Acoustic/Infrasonic Analysis: Location Estimation

How well can we locate events using infrasound? This question has obvious implications for the use of infrasound within the context of nuclear explosion monitoring, and can be used to inform decision makers on the capability and limitations of infrasound as a sensing modality. This paper attempts to answer this question in the context of regional networks by quantifying current capability and estimating future capability using an example regional network in Utah. This example is contrasted with a sparse network over a large geographical region (representative of the IMS network). As a metric, we utilize the location precision, a measure of the total geographic area in which an event may occur at a 95 % confidence level. Our results highlight the relative importance of backazimuth and arrival time constraints under different scenarios (dense vs. sparse networks), and quantify the precision capability of the Utah network under different scenarios. The final section of this paper outlines the research and development required to achieve the estimated future location precision capability.     

大姚6.2级地震的烈度与震害分析

综合震区116个居民点的震害调查资料,系统介绍了2003年7月21日大姚6.2级地震烈度分布的形状、长轴方向及长短轴长度、烈度区面积、范围,各烈度区房屋震害以及供排水系统、供电系统、通迅系统、交通系统和水利系统及地质灾害的特征,并对烈度异常点的场地条件进行了分析.     

近期天山地震带地震活动固体潮调制的统计分析

利用Schuster检验方法, 以潮汐体应力为计算量, 采用2010年1月1日至2012年8月31日天山中东段M_L≥2.0的地震数据, 对天山地震带地震活动受固体潮触发情况从时、 空两方面进行统计分析。 研究结果显示, Schuster检验p值时间窗平滑结果与天山地震带较强地震的发生对应较好, 尤其是2011年11月1日尼勒克6.0级地震之前很长一段时间, Schuster检验p值时间窗平滑结果一直低于潮汐触发地震的阈值0.05, 而尼勒克6.0级地震发生后, 该值迅速恢复到较高水平, 反应了此次地震的发生与固体潮的密切关系; 从Schuster检验p值空间窗平滑结果看, 尼勒克6.0级地震也处于或接近潮汐调制触发地区。 因而, 从时、 空两方面的检验结果看, 尼勒克6.0级地震的发生受固体潮调制明显。     

2017年9月23日朝鲜振动事件记录特征分析

2017年9月23日16时29分在朝鲜丰溪里核试验场发生3.4级地震。本文基于中国地震台网对该地震事件的波形记录,分析认为:该事件不是一次简单的单独过程,虽然事件开始时发生爆破,但事件主体是由断层错动产生的天然地震。这次事件是爆破和天然地震相继发生的复合型事件。     

影响通河地震台地电场观测干扰源的排查分析

通过对通河地震台地电场观测资料的分析判断,利用本台站地电场观测同时段不同测项、附近地电场观测台站地电场观测同时段相同测项对比分析,排查影响本台站地电场观测干扰源,识别干扰形态并进行分析。结果表明,在地电场观测过程中存在可控的干扰源有:人为抽水干扰、工厂运行干扰、农田灌溉干扰等;不可控的干扰源有:雷电干扰、高压直流输电干扰、地电暴干扰等。通过对观测数据干扰形态的识别与排除,对提高地电场数据质量有一定的意义。     

2003年云南大姚6.2、6.1级地震序列特征分析及地震触发研究

本文采用双差定位法对2003年7月21日、10月16日云南大姚先后发生的6.2、6.1级地震及其余震序列进行精定位。结果表明,两个主震的震中位置相当接近,余震序列的空间分布呈明显的线性分布,地震序列精定位后的结果同震源机制解吻合很好,两个地震的发震断层均是近乎直立的右旋走滑断层。此次大姚6.2、6.1级双震,和云南地区大多数其它双震有所不同,余震分布并不呈现共轭分布,而近乎一条直线,两者间有部分重叠,表明两者受控于同一发震断层。相对主震而言,余震都呈不均匀分布,近乎一种单侧分布,6.2级地震的余震集中于主震的西北方向,6.1级地震的余震集中于主震的东南方向,并且6.1级地震是6.2级地震在同一断层向东南端延伸的另一次破裂。库仑破裂静应力变化Δσf研究结果表明,7月21日6.2级地震对10月16日6.1级地震有明显的触发作用,两个主震对断层外余震的发生均有不同程度的应力触发作用,并且2000年姚安6.5级地震对大姚两次地震的发生也有触发作用。     

The Characteristic Analysis and Seismic Triggering Study of the M6.2 and M6.1 Dayao Earthquake Sequences in 2003

INTRODUCTIONTheM6·2 andM6·1 earthquakes occurred successivelyin Dayao,Yunnan Province on July 21and October 16 ,2003 and bothinduced human casualty and economic loss to some extent .Adequatehistorical information reveals that ,earthquakes bigger thanM6·0 in Yunnan are distributed mainlyalong some active tectonic faults and seismic belts . Dayao and Yao an are in the Dianzhong tectonicblock andthere are noapparentfaultsthere(Su Youjing,2004) .Seismic activitylevel inthisregioniswea…     

泰安地震台水平摆1981年以来资料统计分析建模

通过对泰安地震台水平摆20多年光记录和8年数字化记录资料的整理和统计分析,得出泰安台水平摆固体潮年变曲线的规律,将其变化趋势作为一个基本模型,作为将来资料分析的依据,同时将光记录与数字记录年变趋势做对比分析,初步探讨同一峒室同一仪器墩上的这2个仪器趋势变化不尽相同的原因。     

Variable Tsunami Sources and Seismic Gaps in the Southernmost Kuril Trench: A Review

In the southernmost Kuril Trench, the tsunami source regions vary their along-trench extent even among earthquakes occurring within the same segment. Recent studies suggest that the tsunami source of the 1952 Tokachi-oki earthquake (M 8.1) differs from but partially overlaps with that of the 2003 Tokach-oki earthquake (M 8.0). Furthermore, the along-trench extent among the earthquakes seems to differ between deep and shallow portions of the subduction interface. A seismic gap has been recognized along the deep subduction interface between the sources of the 1952 and 1973 earthquakes. We propose that the gap is now larger, including both shallow to deep portions of the interface between the 1973 and 2003 earthquakes. Variability in spatial extent of large subduction earthquakes in both along-trench direction and trench-normal direction makes it difficult to forecast future earthquakes in the southernmost Kuril Trench.     

地震巨灾模型中的随机地震事件集模拟

地震巨灾保险是降低地震灾害风险的有效手段之一,而地震危险性分析是地震巨灾模型的主要分析模块之一。传统的概率地震危险性分析主要是基于潜在震源模型、地震活动性模型和地震动衰减模型等并采用概率方法得到场点的地震危险性值,该危险性表示的是未来所有地震对场点的综合影响。然而,在使用地震巨灾模型进行地震风险分析时需要用到单个地震事件对场点的影响,这就需要根据潜在震源区生成一系列单个地震事件,并计算每个事件对场点的影响。本研究采用蒙特卡洛方法,基于第五代中国地震动参数区划图中所采用的地震活动性模型(潜在震源区及其地震活动性参数),模拟符合我国地震活动时间、空间和强度分布特征的地震事件集。模拟时遵从的基本理论为:地震发生在时间上符合泊松分布,震级分布可用古登堡-里克特定律来描述,空间分布特征则用潜在震源区及其地震发生率来描述。模拟得到的地震事件包含以下参数:时间(年、月、日)、地点(经度、纬度)、深度、震级、断层走向以及衰减特征等。该模拟地震事件集可满足地震巨灾模型中地震风险分析的需求,已应用于我国地震巨灾模型中。     

b值和V4的统计分析及其不确定性对地震危险性分析结果的影响研究

以郯庐地震带为研究实例,基于线性最小二乘法回归原理,采用多种组合方案统计得到多个b值与V4组合,选取最佳组合方案,确定郯庐地震带最优b值和V4值;同时使用概率地震危险性分析方法计算每个组合方案不同超越概率水平下的基岩水平峰值加速度,探讨了地震活动性参数b值和V4的不确定性对地震危险性分析结果的影响程度和规律。本研究方法和结论可供地震活动性分析和地震危险性评价研究时参考,对地震区划和工程场地地震安全性评价均有重要意义。     

Seismic Sources on the Iberia-African Plate Boundary and their Tectonic Implications

—The plate boundary between Iberia and Africa has been studied using data on seismicity and focal mechanisms. The region has been divided into three areas: A; the Gulf of Cadiz; B, the Betics, Alboran Sea and northern Morocco; and C, Algeria. Seismicity shows a complex behavior, large shallow earthquakes (h < 30 km) occur in areas A and C and moderate shocks in area B; intermediate-depth activity (30 < h < 150 km) is located in area B; the depth earthquakes (h 650 km) are located to the south of Granada. Moment rate, slip velocity and b values have been estimated for shallow shocks, and show similar characteristics for the Gulf of Cadiz and Algeria, and quite different ones for the central region. Focal mechanisms of 80 selected shallow earthquakes (8 m_b 4) show thrust faulting in the Gulf of Cadiz and Algeria with horizontal NNW-SSE compression, and normal faulting in the Alboran Sea with E-W extension. Focal mechanisms of 26 intermediate-depth earthquakes in the Alboran Sea display vertical motions, with a predominant plane trending E-W. Solutions for very deep shocks correspond to vertical dip-slip along N-S trends. Frohlich diagrams and seismic moment tensors show different behavior in the Gulf of Cadiz, Betic-Alboran Sea and northern Morocco, and northern Algeria for shallow events. The stress pattern of intermediate-depth and very deep earthquakes has different directions: vertical extension in the NW-SE direction for intermediate depth earthquakes, and tension and pressure axes dipping about 45 ° for very deep earthquakes. Regional stress pattern may result from the collision between the African plate and Iberia, with extension and subduction of lithospheric material in the Alboran Sea at intermediate depth. The very deep seismicity may be correlated with older subduction processes.