辽宁地区M≥5.0地震前4级地震集中活动的震兆研究

本文通过对辽宁地区4次M≥5.0地震和3次典型的ML≥5.0地震前小震活动的统计分析,结果显示,辽宁地区M≥5.0地震前均存在4级地震集中活动的现象,且预期的5级以上地震83%发生在最近1次4级地震后的半年内,震中大部分位于N41°以南,发生在营-海-岫地区的概率超过80%,震级可通过E、T、R三个参量的拟合计算来预测。     

地磁数据处理与地震关系之探

研究了上海崇明、佘山和杭州这3个地磁台的观测资料在2004年4月21日南黄海ML4．0级、5月26日浙江省舟山群岛ML4．3级和11月15日南黄海％4．6级地震前的异常变化特征,结果表明：杭州台和崇明台数字化地磁观测资料分钟值空间差值于4月14日～17日、4月30日、5月8日出现的异常信息很可能是震磁异常信息;杭州台和余山台数字化地磁观测资料分钟值、模拟观测21时值Z分量地磁场相关系数R值分别在震前2天、24天和震前5天、15天出现了超出2σ值的震磁异常变化：崇明和余山地磁台数字化地磁Z分量分钟值的空间差值异常信息在4月21日南黄海尬4．0级地震前后有所显示。但在5月26日舟山群岛ML4．3级地震前不太明显,可能与谈两个地磁台站相距较近日震中距较近有美．     

菏泽—濮阳及附近地区震源深度及波速比变化

计算了发生在濮阳及附近地区(35.5°~36.0°N,115.1°~115.7°E)地震的波速比,并进行T检验。结果表明,研究区内2001~2008年发生的41次ML≥2.6级地震波速比值属于正常变化。通过1970~2008年菏泽—濮阳及附近地区(35.1°~36.0°N,115.1°~115.7°E)发生的ML≥3级地震震源深度分析,发现1983年(11月7日菏泽5.9级地震前,研究区内震源深度变化大(-h=19 km),而5.9级地震后至2008年震源深度浅(-h=13 km)的特点。     

<Emphasis Type="Italic">R/S</Emphasis> analysis of the <Emphasis Type="Italic">Dst</Emphasis> index

The paper addresses estimation of the Hurst exponent for time series of the hourly values of the Dst index for the period from 1957 to 2011. It is found that the Hurst exponent is 0.79–0.94 for yearly intervals and 0.8–1.0 for monthly intervals. Based on R/S graphs, the Dst cycles are identified; they range from 3–4 months to 2.2 years and from 8.5 to 22 years in length. It is shown that a Dst time series can be quite satisfactorily described by an α-stable Levy process.     

地震地磁效应的分形布朗运动的性质及应用

重标极差分析法（R/S,rescaled range analysis method）,是研究分数布朗运动及自然现象的自仿射分形的有力工具之一,对于所有时间序列分析都有着广泛的用途．通过对天水台绝对地磁观测Z分量数据序列R/S分析,计算分段数据序列的Hurst指数H发现,昆仑山口西MS8.1地震和汶川MS8.0地震震前2—3个月,H值减小,分维数D增大,相关系数C为负值．这一动态变化表明,地震前数据序列由持久性序列发展为反持久性序列,观测数据的成分发生了改变．这与地壳内部应力变化和岩石破裂实验结果相符．所以,这一动态变化过程可以看作是强震前的一种前兆信号．      

华北地区ML4级地震平静的分析

结合华北地区MS≥6级地震活动的韵律特征进行了地震幕的划分,并统计分析了华北地区（33°~43°N,108°~125°E）1980年以来出现ML4级地震平静与中等地震的对应情况,主要结论如下：（1）华北地区目前处于第五地震活跃幕的相对平静时段,目前6级地震已经平静16年多,随时可能进入新的地震活动幕;（2）ML4级地震平静对中强地震的前兆意义与当前地震活动所处地震幕的不同阶段有关,在1980—2000年ML4级地震平静与M5级及以上地震有较好的对应关系;2000年之后ML4级地震平静与ML5.2级及以上地震对应关系较好;（3）2013年11月23日山东莱州ML5.0级地震打破华北地区ML4级地震平静189天,虽然在预报期限内没有ML5.2级以上地震,但是2014年4月1日发生黄海ML5.1级地震,鉴于目前震群活跃,仍要警惕华北地区出现更大地震的危险。     

Temporal and spatial variations of seismicity scaling behavior in Southern México

R/S analysis is used in this work to investigate the fractal correlations in terms of the Hurst exponent for the 1998–2011 seismicity data in Southern Mexico. This region is the most seismically active area in Mexico, where epicenters for severe earthquakes (e.g., September 19, 1985, M_w = 8.1) causing extensive damage in highly populated areas have been located. By only considering the seismic events that meet the Gutenberg–Ritcher law completeness requirement (b = 0.97, M_GR = 3.6), we found time clustering for scales of about 100 and 135 events. In both cases, a cyclic behavior with dominant spectral components at about one cycle per year is revealed. It is argued that such a one-year cycle could be related to tidal effects in the Pacific coast. Interestingly, it is also found that high-magnitude events (M_w ≥ 6.0) are more likely to occur under increased interevent correlations with Hurst exponent values H > 0.65. This suggests that major earthquakes can occur when the tectonic stress accumulates in preferential directions. In contrast, the high-magnitude seismic risk is reduced when stresses are uniformly distributed in the tectonic shell. Such cointegration between correlations (i.e., Hurst exponent) and macroseismicity is confirmed for spatial variations of the Hurst exponent. In this way, we found that, using the Hurst exponent standpoint, the former presumed Michoacan and the Guerrero seismic gaps are the riskiest seismic zones. To test this empirical finding, two Southern Mexico local regions with large earthquakes were considered. These are the Atoyac de Alvarez, Guerrero (M_w = 6.3), and Union Hidalgo, Oaxaca (M_w = 6.6), events. In addition, we used the Loma Prieta, California, earthquake (October 17, 1989, M_w = 6.9) to show that the high-magnitude earthquakes in the San Andreas Fault region can also be linked to the increments of determinism (quantified in terms of the Hurst exponent) displayed by the stochastic dynamics of the interevent period time series. The results revealed that the analysis of seismic activity by means of R/S analysis could provide further insights in the advent of major earthquakes.     

Spatial and temporal variations in summer precipitation in Japanese mountain areas

We examined spatial and temporal variations in precipitation measured during summer season between 1976 and 2007 for 28 stations located in mountain areas across Japan using the amount of precipitation (Pr), the mean depth of precipitation events (η), and the inverse of the mean interval times (λ). We obtained positive correlations between the period mean Pr (Pr ) and the period mean η ( ) and between Pr and the period mean λ ( ) for the 28 stations. Pr was more strongly related to than to , indicating the spatial variations in Pr that are primarily related to the variations in . In addition, Pr was more strongly related to η than to λ for most stations on the basis of data for 1976–2007, indicating that the year‐to‐year variations in Pr are primarily related to η. We also examined temporal trends in Pr, η and λ for 1976–2007 and found no systematic trends for 23 of the 28 stations, suggesting long‐term trends that are not common in mountain areas of Japan. The relationships between Pr and and between Pr and η presented in this study enable us to generate a temporal precipitation distribution pattern based on only Pr and Pr data, respectively. Furthermore, probabilistic stochastic hydrological models require precipitation characteristics as input; thus, this study contributes to the determination of hydrological cycles and their possible future changes in Japanese mountain areas and therefore to water resource management. Copyright © 2010 John Wiley & Sons, Ltd.     

Changes of Ozone Content at Middle Latitudes During Forbush Decreases in Cosmic Rays

The variations of total ozone at Alma-Ata (43°N, 76 °E) and ozone profiles obtained by balloon sounding at Tateno (36°N, 140°E), Wallops Island (38°N, 75°W) and Cagliari (39°N, 9°E) in the periods of Forbush decreases (FD) in galactic cosmic rays have been analysed. A decrease of total ozone was observed in the initial stage of the FD and an increase 10–11 days later. The average total deviations calculated using the superposed epoch method for 9 FD events are equal to 30 D. U. in the positive and to –18 D. U. in the negative phase. The changes of average ozone profiles, associated with 26 FD events, are more significant in the lower stratosphere and upper troposphere. The decrease of the partial ozone pressure at a height of 12–15 km is about 30 mb. These vertical variations of ozone coincide with the average changes of the respective temperature profiles. A cooling, on the average, of 3°C was observed at 12–15 km, and a heating of 4°C below this level.     

粤闽交界及其近海地区地震活动分析

结合东南沿海地区的地质构造背景、地震活动特点,研究粤闽交界及其近海地区(N 22.80°~24.00°、E116.50°~118.00°)地震活动特征,结果表明此区域:1具备中强地震活动的构造背景;2现代小地震呈北东方向密集成带分布在南澎列岛附近,与北东向滨海断裂的方向一致;3 6级以上地震序列类型多属主余型;4 1971年有小震记录以来,一直存在背景性的ML2级左右地震活动;ML4级以上地震活动成丛分布特征明显;中等地震(ML4~5级)的发生与本区小震活动增强之间无明显关联;当出现年平均b值低于平均值、且较上一年b值下降幅度≥0.5时,可能预示本区进入ML4级地震活跃时段,东南沿海地震带在未来1~2年内可能有中强或以上地震发生;ML4.5级以上地震前,应变能释放曲线存在加速变化。     

A scale-invariant approach to flood-frequency analysis

In order to study historical flood-frequency records we plot the log of the number of floods on a river per unit time in which the peak discharge exceeds a specified value against the log of that value. For ten benchmark stations we find good correlations with scale-invariant (fractal) statistics. We suggest that the underlying physical processes associated with the generation of floods are sufficiently scale invariant over time scales from one to one hundred years that they provide a rational basis for the application of scale-invariant statistics. Our results fall within the range of flood-frequency estimates made by other statistical techniques. We propose that the ratio of the ten-year peak discharge to the one-year peak discharge is a quantitative measure of flood potential. With scale invariance is also the ratio of the one-hundred year flood to the ten-year flood. We find that the values of for ten stations on rivers throughout the country range from 2.04 to 8.11 and find strong regional variations that can be correlated in terms of climate. Our results are consistent with the observed fractal statistics in sedimentary sections. We have also carried out R/S analyses for the ten stations and have obtained values of the Hurst exponent. We find that the Hurst exponent cannot be used for flood-frequency forecasting.     

A scale-invariant approach to flood-frequency analysis

In order to study historical flood-frequency records we plot the log of the number of floods on a river per unit time in which the peak discharge exceeds a specified value against the log of that value. For ten benchmark stations we find good correlations with scale-invariant (fractal) statistics. We suggest that the underlying physical processes associated with the generation of floods are sufficiently scale invariant over time scales from one to one hundred years that they provide a rational basis for the application of scale-invariant statistics. Our results fall within the range of flood-frequency estimates made by other statistical techniques. We propose that the ratio of the ten-year peak discharge to the one-year peak discharge is a quantitative measure of flood potential. With scale invariance is also the ratio of the one-hundred year flood to the ten-year flood. We find that the values of for ten stations on rivers throughout the country range from 2.04 to 8.11 and find strong regional variations that can be correlated in terms of climate. Our results are consistent with the observed fractal statistics in sedimentary sections. We have also carried out R/S analyses for the ten stations and have obtained values of the Hurst exponent. We find that the Hurst exponent cannot be used for flood-frequency forecasting.     

1982年卢龙地震前后的小震震源参数

1982年10月19日,在唐山余震区的东北端卢龙,发生了一次ML=6.2(按北京电信传输台网的目录)的地震(3957'N,11904'E).为了监视卢龙地震前后小震震源参数的变化,本文考察了唐山-卢龙地区自1980年1月至1984年6月的情况.利用P波初动半周期,测定了160次ML=2.7——4.3的地震的震源参数.在所研究的震级范围内,初动半周期和震源半径不随ML而增大,应力降则随ML而增大.应力降的数值在0.1——50MPa的范围内变化,且主要集中在1MPa和5MPa之间.因此本文认为,对此地区,5MPa以上为高应力降,1MPa.以下为低应力降.该地区地震的空间分布表明,高应力降事件与随后发生的ML5的地震有明显的关系.在卢龙地震前一年多里,整个地区内的高应力降事件减少,低应力降事件增多;但在卢龙地震的震中附近发生了两次高应力降事件.      

Planetary Wave Periods in <Emphasis Type="Italic">foF</Emphasis>2 Time Variations Based on Winter Data from Kaliningrad Station in 2008−2010

The study presents the results of the analysis of the F2-layer critical frequency variations obtained for the winter periods of 2008–2010, during which sudden stratospheric warmings were observed. The data were obtained at Kaliningrad ionospheric station (54.6° N, 20° E) with the Parus digital ionosonde in standard sounding mode. The mean daily foF2 values were used in the analysis. The results of spectral analysis based on continuous wavelet transform showed that, during all of the warmings that occurred in 2008–2010, the foF2 time variations demonstrated the presence of wave processes with periods of approximately 5?6 days, as well as more extended processes with periods of ~10?13 and 23?30 days. These periods coincide with the characteristic periods of planetary waves observed in the mesosphere during sudden stratospheric warmings, while the 13- and 30-day periods can be conditioned by the influence of the Sun.     

Harold Edwin Hurst: the Nile and Egypt,past and future

ABSTRACT

H.E. Hurst spent some 60 years studying the Nile for the Egyptian government, and laid the foundation for a monumental set of hydrological records and investigations. His studies of the size of over-year reservoirs needed to maintain a given yield from Nile flows showed that this was greater than that based on random series. This finding, known as the Hurst phenomenon, was confirmed by other natural series and led to important advances in practical and theoretical statistics. His work led to the design of the Aswan High Dam and to continued research in Egypt.

Editor D. Koutsoyiannis; Guest editor E. Eris     

Quasi-wave variations in <Emphasis Type="Italic">foEs</Emphasis> during stratospheric warmings of 2008–2010 according to data from Kaliningrad ionospheric station

The results of analysis of variations in the sporadic layer critical frequency (foEs) for winter periods of 2008–2010 in which sudden stratospheric warmings were observed are presented in the paper. The data were obtained at Kaliningrad ionospheric station (54.6° N, 20° E) by a Parus digital ionosonde under the usual sounding regime with an interval of 15 min. Daily mean values of foEs were used for the analysis. Solar and geomagnetic activity remained low during the periods under study, making it possible to relate the quasiwave time variations in foEs to the parameters of stratospheric warmings. The results of spectral analysis performed on the basis of continuous wavelet transform showed that, during all warmings occurring in 2008–2010, time variations in foEs show the presence of wave processes with a period of an order of 5 days and longer ones with a period of ~10—11 days. These periods coincide with characteristic periods of planetary waves observed in the atmosphere during sudden stratospheric warnings.     

Variations in the total electron content during the powerful typhoon of August 5–11, 2006, near the southeastern coast of China

The variations in the total electron content (TEC), obtained from the data of 11 ground-based GPS stations in the region (5°S–80°N; 110–160°E) in the period August 2–15, 2006, have been analyzed in order to search for possible ionospheric manifestations of the SAOMAI powerful typhoon (August 5–11, 2006) near the south-eastern coast of China. The global TEC maps (GIM) have also been used. In the region of the typhoon action during the magnetic storm of August 7, 2006, an intensification of the TEC variations in the evening local time within the 32–128 min periods range was detected. However, this effect was most probably caused by the dynamics of the irregular structure of the equatorial anomaly and by the disturbed geomagnetic situation (Kp ～ 3–6, Dst varied from ?74 to ?153 nT). The analysis of the diurnal variations in the absolute values of TEC and TEC variations with periods of 2–25 min did not reveal a substantial increase in the intensity and changes in the spectrum of the TEC variations in the period of typhoon action as compared to the adjacent days. Thus, we failed to detect ionospheric disturbances unambiguously related to the SAOMAI typhoon.