Estimating maximum magnitude earthquakes in Iraq using extreme value statistics

Summary. Extreme value theory is used to estimate maximum magnitude earthquakes in Iraq (29–38°N, 39–48°E). The seismicity file for the period 1905–1982 is used to determine the recurrence relationship as well as the parameters of Gumbel types I and III asymptotic distributions.
The statistical parameters are estimated by both least squares and maximum likelihood techniques. Results show that although the least squares upper magnitude is closer in value to actual earthquake magnitude, the maximum likelihood approximation to the third distribution appears to show a better overall fit to the data sample. This result is reflected in the calculated probability of occurrence of earthquake risk over various design periods.     

The first and third asymptotic distributions of extremes as applied to the seismic source regions of India and adjacent areas

The seismic source regions are identified on the basis of spatial and temporal distributions of shocks (1900–1989), recurrence relations and the tectonic architecture of the Indian subcontinent and adjoining areas. The probable occurrence of the maximum magnitude earthquake is estimated using the theory of extreme values of Gumbel. The parameters of the first and third asymptotic distributions of extremes and their uncertainty values are computed for the seven identified seismic source regions of India and adjacent areas. The third-type distribution curve is preferable to the first type in all the regions, as revealed by the χ² test. The results of the third asymptotic distribution indicate the upper bound to earthquake magnitude w is equal to 8.94 ± 0.21 for Assam, 8.56 ± 0.29 for Bihar-Nepal, 8.43 ± 0.10 for Kangra, 8.97 ± 0.27 for Hindukush, 7.61 ± 0.24 for Pakistan-Cutch, 7.34 ± 0.12 for Koyna and 8.98 ± 0.27 for Andaman Sea seismic source regions. The predicted most probable largest earthquake magnitude is computed for return periods of 10, 20, 50, 75 and 100 yr in each source region.     

Perceptible earthquakes in the United Kingdom

Summary. Earthquake occurrence in the United Kingdom is analysed using Gumbel's third type asymptotic distribution of extreme values. Uncertainties in both the parameters and predictions derived from the Gumbel distribution are obtained and it is shown that an earthquake with body-wave magnitude slightly over five is the one most likely to be perceived at any point in the United Kingdom.     

乌鲁木齐河洪水频率分析

本文通过对乌鲁木齐河年最大洪峰流量实测资料与历史洪水资料的分析，选定了正态分布，对数正态分布，三参数对数正态分布，Ｇｕｍｂｅｌ分布，Ｐｅａｒｓｏｎ－Ⅲ型分布和对数Ｐｅａｒｓｏｎ－Ⅲ型分布等６种线型，利用极大似然法对各种分布函数的参数进行了最优估计。     

Non-Poissonian earthquake occurrence in coupled stress release models and its effect on seismic hazard

Most seismic hazard estimations are based on the assumption of a Poisson process for earthquake occurrence, even though both observations and models indicate a departure of real seismic sequences from this simplistic assumption. Instrumental earthquake catalogues show earthquake clustering on regional scales while the elastic rebound theory predicts a periodic recurrence of characteristic earthquakes on longer timescales for individual events. Recent implementations of time-dependent hazard calculations in California and Japan are based on quasi-periodic recurrences of fault ruptures according to renewal models such as the Brownian Passage Time model. However, these renewal models neglect earthquake interactions and the dependence on the stressing history which might destroy any regularity of earthquake recurrences in reality. To explore this, we investigate the (coupled) stress release model, a stochastic version of the elastic rebound hypothesis. In particular, we are interested in the time-variability of the occurrence of large earthquakes and its sensitivity to the occurrence of Gutenberg–Richter type earthquake activity and fault interactions. Our results show that in general large earthquakes occur quasi-periodically in the model: the occurrence probability of large earthquakes is strongly decreased shortly after a strong event and becomes constant on longer timescales. Although possible stress-interaction between adjacent fault zones does not affect the recurrence time distributions in each zone significantly, it leads to a temporal clustering of events on larger regional scales. The non-random characteristics, especially the quasi-periodic behaviour of large earthquakes, are even more pronounced if stress changes due to small earthquakes are less important. The recurrence-time distribution for the largest events is characterized by a coefficient of variation from 0.6 to 0.84 depending on the relative importance of small earthquakes.     

珠江三角洲地区风暴潮重现期及增水与环境要素的关系

珠江三角洲地区是我国海岸中台风暴潮最严重的区域之一,受全球变暖和海平面上升影响,该地区风暴潮增水重现值将出现显著的变化。本文采用耿贝尔方法和皮尔逊Ⅲ型分布法,分别计算了珠江三角洲地区11个潮位站的最大增水值的重现期,并对计算结果进行了比较,绘制了风暴潮增水重现值分布曲线。结果表明大部分潮位站的耿贝尔分布曲线与经验频率点吻合程度较好,少数潮位站的皮尔逊Ⅲ型分布曲线与经验频率点吻合程度较好,两种方法结合起来效果最佳;分析了该地区风暴潮重现期的基本特征;最后总结了风暴潮与台风路径、天文潮以及地形之间的关系。该计算结果将为政府规划设计部门决策提供参考,对风暴潮预报、海岸工程设计和估计风暴潮造成的损失提供科学依据。     

Likelihood analysis of earthquake catalogues

We apply several classes of stochastic multidimensional models to statistical analysis of earthquake catalogues using likelihood methods. We investigate the importance of including different earthquake parameters in the model: epicentral coordinates, hypocentral depth, time limits for interearthquake interaction, and especially spatial distribution of earthquakes as well as spatial aftershock patterns. Results of this study combined with other investigations, suggest that most distributions controlling earthquake interaction have a fractal or scale-invariant form. Developed models are used for statistical analysis of several earthquake catalogues to evaluate parameters of earthquake occurrence. These parameters are shown to be similar for shallow earthquakes of different magnitude ranges and seismogenic regions, confirming self-similarity of the earthquake process. Whereas intermediate earthquakes seem to emulate the pattern of shallow earthquake occurrence, albeit at a much smaller aftershock rate, deep earthquakes differ significantly in their properties. Predictability of standard shallow earthquake catalogues has been analysed; we present evidence that for the best available catalogues the predictability is close to 10 bits per earthquake. Several synthetic earthquake catalogues have been created and processed through the likelihood inversion scheme. The results from likelihood analysis of these catalogues confirm our approach.     

郑洛地区史前聚落遗址人居环境宜居度指数模糊综合评价

以地貌、土壤、坡向、坡度、高程5个指标构建郑洛地区史前聚落遗址人居环境指数模糊综合评价体系,使用基于地理探测器的因子探测法确定各单因素权重,根据环境驱动因子分级标准及等级值,采用梯形和三角形隶属函数计算单因素评价值,再使用加权平均的综合评价类型和等距法,得到了郑洛地区史前聚落遗址人居环境指数综合等级,运用SPSS数据探索功能,分析宜居度最高地区的具体环境特征,并分别以仰韶后期和龙山时期的实际遗址分布数据对该等级评价系统的准确性进行验证。研究结果表明,该模型评价结果较为准确可靠。     

基于社会属性的北京市居民群体空间自相关分析

以北京市各街道居民为调查研究对象,利用问卷调查数据,使用因子生态分析和空间自相关分析技术,将被调查人群综合性地分为五类,即低潜力差现状型人群、高潜力差现状型人群、高潜力中现状型人群、中潜力中现状型人群和高潜力优现状型人群。通过对不同类人群的总体和局部空间自相关分析,得出结论:居民群体空间聚集现象明显。其中低潜力差现状型人群在通州、黑庄户等街道聚集,高潜力差现状型人群在以东直门街道为圆心的一个扇形区域聚集,中潜力中现状型人群多居住于中心城区,高潜力中现状型人群多在天通苑、四季青一带和南苑街道附近聚集,高潜力优现状型人群主要聚集在四季青至永定路街道的区域。     

Seismic risk in southern Europe through to India examined using Gumbel's third distribution of extreme values

Summary. A technique is described for the analysis of seismicity using Gumbel's third asymptotic distribution of extreme values. Seismicity of southern Europe through to India, nominally for the period 1900–74, is subdivided in a cellular manner, without recourse to tectonic discrimination between regions, and a covariance analysis on the three parameters of Gumbel's distribution is performed for each cell of seismicity. The results indicate that the upper bound to the magnitude of earthquake occurrence is often uncertain although it is discernible, while curvature of the earthquake occurrence distributions is usually established. Uncertainties in the forecasts of largest earthquakes, with a return period of 75 yr, are distinctly improved by taking into account the large and negative covariance which is measured between the curvature and upper bound to earthquake magnitude for the observed seismicity. These results are then used to map seismic risk for southern Europe through to India.     

Earthquake intensity attenuation pattern in the United States

Summary. Attenuation of earthquake intensities with epicentral distance was studied by analysing the intensity data for 39 earthquakes in the United States. Attenuation of MM intensity ( I ) with distance (Δ km) follows a simple relation of the type log I = log I ₀ - m Δ, where I ₀ is the intensity at the epicentre and m is a constant. Slope m is found to be inversely proportional to the square of the focal depth. Intensity attenuation pattern in the United States in general can be represented by a unified relation I/I ₀= exp [-(0.8999/ h ²+ 0.0014)Δ] where 16km ≤ h ≤ 60km. Intensities were calculated with the help of this equation and a good agreement with the observed intensities were found. A comparative study has also been made between the attenuation relations applicable to India and the United States.     

上海地区不同重现期的风速估算研究

基于上海气象站历史风速观测资料,采用极值I型和皮尔逊III型分布估算了上海市不同重现期最大风速的时间变化以及各区（县）不同重现期最大和极大风速的空间分布。结果表明,1901~2011年,上海市10、30、50和100 a重现期的最大风速分别为21.0、24.9、26.7和29.2 m/s。1974~2011年期间,上海各区（县）10 m高度10、30、50和100 a重现期的最大风速都是以南部沿海地区南汇或金山最大,分别为19.0、21.4、22.6和24.1 m/s;各重现期极大风速也是以南汇或金山最大,分别为32.3、36.4、38.4和41.0 m/s。中心城区各重现期的最大和极大风速都最小。     

Modern Diatom Assemblages in Surface Sediments from Estuarine Systemsin the Southeastern Buenos Aires Province, Argentina

Paleoecological reconstructions of Holocene sea-level changes in Argentinean coastal regions were based mainly on ecological data gathered from other regions, as there was a lack of information on modern estuarine diatom distributions. The aim of the present work was to assess the spatial variation of diatom assemblages in two representative estuaries of Argentina in order to gather ecological information for paleoecological reconstructions in the region. The two selected estuaries have different geomorphologic features and salinity regimes: Mar Chiquita Lagoon is shallow, which prevents the development of a stable salinity gradient as it occurs in the Quequén Grande River. Surface sediment samples were taken from selected stations representative of the environmental gradient from the inlet to the inner reaches of both estuaries. Cluster analysis defined three diatom zones at Mar Chiquita: marine/brackish assemblages dominate the inlet (zone I), where salinity, tidal range and current speed are higher. The brackish/freshwater tychoplankton Staurosira construens var. venter and Staurosirella pinnata dominate the inner lagoon (zone II), where environmental conditions are very variable and concentrations of suspended sediments are higher. Brackish/freshwater euryhaline diatoms dominate the headwaters (zone III). On the other hand, the Quequén Grande River was divided into three diatom zones: coastal taxa are distributed at the inlet (zone I), while the middle estuary (zone II) is dominated by brackish/freshwater euryhaline taxa. At the upper estuary region (zone III), freshwater diatoms dominate, and the halophobous Nitzschia denticula increased in abundance values. Diatom distributions were most closely related to the salinity gradient at Quequén Grande River than at Mar Chiquita Lagoon. Fossil data of a sequence from Mar Chiquita Lagoon (Las Gallinas Creek) were compared to the modern data set in order to search for analogies between fossil and modern diatom assemblages. DCA results showed that fossil diatom assemblages have modern counterparts. Most diatom assemblages of Las Gallinas Creek fall within Mar Chiquita zone III, representing a shallow brackish/freshwater environment, with low salinity fluctuations (~1–9‰) and no tidal influence. Therefore, our modern diatom data provide useful analogs to interpret paleoenvironments in the region.     

江苏省劳动密集型产业集群化转移的空间路径及机理研究

以江苏省为区域案例,根据劳动密集系数选取3类10种产业,采用区位基尼系数、计量经济学模型以及纵向比较和横向比较相结合的方法,分析江苏省域不同类型劳动密集型产业集群化转移的趋势及空间路径。结果发现：江苏劳动密集型产业集群化转移趋势明显,Ⅰ、Ⅱ类劳动密集型产业以苏南地区比重下降明显,苏北苏中地区上升较快、Ⅲ类劳动密集型产业以苏南地区内部重新分配为主的特征;总体呈现由苏南向外推移的中心-外围式空间格局,产业集群化转移遵循以苏南为转移中心,苏北为产业承接外围的三阶梯、“一心两翼一腹地”的空间路径。最后,结合中心-外围理论,分析了劳动密集型产业集群化转移的内在机理。     

The mechanisms of shallow earthquakes and the monitoring of a comprehensive test ban

The ability of seismological criteria to identify earthquakes from underground explosions depends partly on the orientation of the earthquake source. Well-determined double-couple moment tensor solutions for a large number of earthquakes have been published in the Harvard centroid moment tensor (CMT) and United Slates Geological Survey (USGS) catalogues. Statistical analyses of these catalogues indicate that the distribution of the orientation of earthquake mechanisms is not random. The distribution of the T axes shows significant clustering around the downward vertical, indicating that a larger number of earthquake mechanisms radiate compressional P -wave energy to teleseismic distances from near the maximum of the radiation pattern than is predicted if earthquake sources are randomly oriented double couples. The clustered T axes correspond to compressional dip-slip mechanisms, and it is this type of mechanism which is believed to cause both the m _b: M _s (the ratio of body-wave to surface-wave magnitude) and first-motion criteria to misidentify an earthquake as an explosion.     

Decision-theoretic limits on earthquake prediction

I apply Decision Theory to the question of how accurate earthquake predictions must be to serve as a reliable basis for action. Even with optimistic estimates of the parameters involved, the lower bound on the required accuracy is extraordinarily demanding, being over 10 times higher than that of current meteorological forecasts. Given the abruptly self-organizing nature of earthquakes, it is extremely unlikely that precursors can attain such levels of accuracy. I therefore conclude that prediction of major earthquakes is, in any practical sense, impossible.     

中国地震灾害人口死亡风险定量评估(英文)

基于地震灾害风险形成机理,在建立人口震害脆弱性曲线与确定地震发生参数的基础上,本文利用评估模型对我国Ⅴ-Ⅺ地震烈度下各县域单元的人口死亡风险进行评估并分析其空间分布格局。主要研究内容有:(1)首次采用基于过去—现在—未来的多方面地震孕灾环境资料来处理地震发生的可能性。具体综合历史地震综合烈度、地震活动断裂带分布、地震动峰值加速度三方面来确定全国2355个县域单元的地震发生参数;(2)利用1990-2009年我国历史地震灾情数据,对地震烈度与人员死亡率之间进行线性拟合,建立适合我国地震灾害风险评估的震害人口死亡脆弱性曲线;(3)利用震害风险评估模型对我国各县域单元的人口死亡风险进行定量评估,并分析风险空间分布格局,彻底摸清Ⅴ-Ⅺ地震烈度下我国各县域单元的地震灾害人口死亡风险。研究表明:在不同地震烈度下,我国广大的东、中部地区面临更高的风险,而西部的人口死亡风险相对较低。高风险区域呈零星状分布于山东与江苏大部、安徽北部、黑龙江与吉林东部等人口分布较密集且孕灾环境发育完备的区域。而无风险区域在全国范围内呈斑块状散布,分布格局基本保持不变。     

Surface-wave study of the Labrador Sea earthquake 1971 December

Source parameters of an earthquake that occurred on the continental slope off the coast of Labrador, the first earthquake known to have occurred in this region, are determined by using body-and surface-wave data. The focal mechanism is of the dip slip type and the focal depth is 16 km. The local deviatric stress field applied to the region is estimated to be compressional oriented normal to the North American continent. The observed surface-wave spectra are characterized by a sharp fall-off near the period T = 15–20 s. This observed fall-off is attributed to thick sediment at the continental slope. Consequently, when an earthquake is not located within a continental area, the source parameter determination using short-period surface waves is restricted in application.     

The spatial stability of alcohol outlets and crime in post‐disaster Christchurch,New Zealand

The devastating Canterbury Earthquakes of 2010 and 2011 left an indelible mark on the city of Christchurch. The social and economic upheaval that immediately followed the Earthquakes has, in time, been replaced with a period of rebuild and transformation. In this study we investigate the effects that the Canterbury Earthquakes had on two important and inter‐related phenomena in the city: alcohol availability and crime. More specifically, we investigate how alcohol outlets and crime across six different categories changed in magnitude and spatial distribution pre‐ (end‐2009) and post‐ (end‐2014) earthquake. We do this using a variety of geospatial techniques including a relatively new method: the spatial point pattern test which allows for the identification of changes in spatial patterns at the local level. Results indicate that both alcohol outlets and crime have decreased in magnitude since the Canterbury Earthquakes. Using the spatial point pattern test we found statistically significant differences in spatial point patterns for both alcohol outlets and all crime types pre‐ to post‐earthquake. The similarity in the differences of the spatial distributions of alcohol outlets and crime provides a first empirical clue of their potential association in the city post‐earthquake.