Changes in the diurnal periodicity of Southern California earthquakes in the neighborhood of the catalog magnitude of completeness

Dependence of the diurnal periodicity phase diagrams for Southern California earthquakes on their magnitude is studied with the Rayleigh-Schuster method. The highest statistical significance of diurnal periodicity is characteristic for the weakest non-representative earthquakes occurring in the night rather than in the daytime. The statistical significance of the earthquake diurnal periodicity decreases as the earthquake magnitude increases. Diurnal periodicity disappears in the neighborhood of the catalog magnitude of completeness. It appears again with a reasonably high level of statistical significance in the magnitude range exceeding the magnitude of completeness. However, its phase becomes opposite: strong earthquakes are more frequent in the daytime. Phase diagrams of different spatial earthquake sample groups are compared, and the night and daytime earthquake recurrence graphs are studied.     

Evidence of geodynamical processes in the ancient crust from the seismoacoustic model of the kola superdeep borehole

The spectral-profile and wavelet analyses are applied for estimating the periodicity in the depth variations of the elastic wave velocities in the detailed seismoacoustic model of the Kola Superdeep Borehole. The geological confinement of the revealed multiscale periodicity and its relationship with the geodynamical processes in the Earth’s crust are considered. The hierarchical sequence of the sizes of the blocks identified in the section is determined; this hierarchy is consistent with the geophysical structure of the medium.

     

Diurnal periodicity of the representative earthquakes in Greece

The diurnal periodicity of seismic events of different energy from the Greece earthquake catalog was studied. Earthquake samplings of different energy with a known level of magnitude of completeness were compiled. Parameters of the diurnal periodicity of earthquakes in different time and magnitude intervals were analyzed. Significant diurnal periodicity of earthquakes with M ≤ 4.1 was revealed. The most important result of the paper is the discovery of the diurnal periodicity of the representative earthquakes with M = 3.2–4.1. The diurnal periodicity of representative earthquakes cannot be explained at the base of the prevailing hypothesis considering the diurnal periodicity of earthquakes as an apparent phenomenon resulting from diurnal changes in the real sensitivity of the seismic network due to diurnal variations of seismic noise.     

Features of the diurnal periodicity of earthquakes in Japan

The features of the diurnal periodicity of earthquakes with different energies in Japan are studied. The spatiotemporal parameters of different earthquake sets are investigated in detail using various techniques including analyses of amplitudes, dispersion, spectra and correlation. The phases of seismic flows are studied using the modified Rayleigh-Schuster method. Lomb-Scargle periodograms are used to study the frequency of variations in seismicity. The parameters of the sets of earthquakes having different energies obtained in this study indicate changes in phase of the diurnal periodicity of earthquakes to the opposite near the magnitude of completeness. The very clear midday effect is noted.     

中国华北和南北地震带北段8级大震发生的时间规律

用以25年为周期的三性分布拟合华北和南北地震带北段8级大震发生的时间分布,发现拟合较好,因之在今后预测8级大震时可作为参考。三性分布是指周期性、倍周期性和每个周期的黄金分割性组成的时间分布。     

On the causes of unordinary periodicity of earthquakes

The diurnal periodicity of seismic events from three earthquake catalogs of Fennoscandia and Turkey is studied. The shape of diurnal distribution of seismic events in all the catalogs under investigation is similar to the unordinary diurnal periodicity of earthquakes described in previous papers. The principal feature of the diurnal periodicity of seismic events revealed in this paper is a wide maximum of the events in the day time. The very reliable conclusion is made that it is caused by presence of a great amount of quarry blasts in the catalogs.     

Diurnal periodicity of earthquakes and its seasonal variations

Analysis of earthquake catalogues on 14 world regions has revealed a distinct diurnal periodicity of seismic events in all of them. The amplitude of the diurnal variations usually decreases with an increase in earthquake energy, although in some regions, the time series of strong earthquakes also demonstrate diurnal periodicity. Earthquakes are more frequent at night. The acrophase of the course of diurnal seismicity correlates with geographic longitude. The Rayleigh — Schuster hodographs of diurnal periodicity demonstrate sharp changes (kinks) in the vicinity of the equinox and solstice moments. The annual hodograph of the diurnal periodicity of earthquakes is distinctly divided by the equinox moments into segments with different slopes. The defined segments differ in the amplitude and acrophase of the course of diurnal seismicity. The data imply influence of the mutual positions of the Sun and Earth on seismicity in different world regions. Possible mechanisms responsible for such influence are discussed.     

Periodicity of orogeny

The periodicity of orogeny is discussed in terms of sea floor spreading, plate tectonics and recent orogenic theory. The confusion in discussions of periodicity is due to the lumping of three distinct features together; continental edge orogenies, continental collision orogenies and features due to mid-oceanic rises. Orogenic periodicity is only well developed for continental edge orogenies. This is related to periodicity in mid-oceanic rise activity over the world. If this is shown to be untrue, there is no periodicity to orogeny over the world; and periodicity is only developed on continental edges controlled by one mid-oceanic rise.     

东北地区地震活动的Rydelek-Sacks周期性检验和震级-周期谱研究

为检验中国东北地区地震活动可能存在的周期性特征和深、浅源地震在周期性活动上的相关性,利用Rydelek-Sacks检验方法和不同的地震目录,考虑了地震震级的选取对周期性特征识别可能存在的影响,并在震级-周期谱中进行了比较研究.对该地区1970-2009年ML≥4.5浅源地震、1920-2009年Ms≥5.0浅源地震和1...     

辽西地区地震活动的周期性现象

以应变能和震级为指标,对辽西地区1966-1991年间的地震活动进行了周期探讨。结果表明此间地震活动呈现了较好周期性。如果该周期性继续保持,那么,从1991年开始,辽西地震活动进入低水平活动阶段。估计在1994年前后开始出现转折。     

On the 60-year signal from the core

The decadal variation in the length of day and in the Earth's magnetic field is analyzed by empirical mode decomposition (EMD). The existence of a periodicity of about 60-years in the Earth's angular velocity has often been inferred and is confirmed here, with a new estimate of approximately 62 years. The existence of a similar periodicity in the geomagnetic field has been controversial. From the time series analyses presented here of the magnetic declination at 10 observatories, it is concluded that a geomagnetic periodicity of about 62?±?3 years does exist. A similar analysis of the magnetic inclination at five observatories gives a period of 58?±?5 years. The declination data from four observatories is found to correlate with the length of day signal, with a correlation coefficient of approximately 0.6.     

Search for Technogenic Effects in the Time Series of Earthquakes in Greece

A search for technogenic effects in the time series of earthquakes in Greece is carried out. The ine- quality of intra-week distributions of earthquakes including the events of M ≥ 3.7 is shown. Sharp changes in the pattern of Rayleigh-Schuster’s hodograph for the diurnal periodicity of earthquakes were revealed. They are located in the time vicinity of the moments of the equinox. The result supports the idea of the natural gen- esis of the diurnal periodicity of earthquakes and the important role of the Sun.     

Patterns in the daily periodicity of low magnitude seismicity in Kamchatka

A daily periodicity in small (K ≤ 8. 0) Kamchatka earthquakes has been detected, with the maximum occurring during the nighttime. The effect was not observed throughout the area of study, but only in several zones. We show that the results are not affected by human and weather factors. A hypothesis is put forward to explain the physical causes of the effect, viz., that the daily periodicity of small earthquakes could be due to natural VLF electromagnetic radiation acting on the geologic medium. It is pointed out that the effect is related to the previously identified effect of natural electromagnetic radiation modulating the intensity of geoacoustic emission from rocks.     

A revised range of variability approach considering the periodicity of hydrological indicators

Comprehensively assessing the hydrological alteration of river flows is a prerequisite for the scientific management, protection, and restoration of rivers. The range of variability approach (RVA), which is based on indicators of hydrological alteration (IHAs), is a widely used method to evaluate hydrological alteration. However, the RVA only considers the frequency of each IHA, neglecting the equally important temporal order of these IHAs. The order of IHA event can be reflected by its periodicity. On the basis of the RVA, in this study, we propose a revised RVA that considers both the frequency and periodicity of IHAs. In the revised RVA, first, the periodic time of each IHA is identified; next, the periodicity alteration (P) of river flow is calculated by comparing the periodic times of the pre‐impact‐period and post‐impact‐period IHAs; finally, P and the frequency alteration(D) in traditional RVA are incorporated into a single index (H) to reflect the overall hydrological alteration. A case study of the Xi Dayang (XDY) Reservoir and rearranged flow suggests that the traditional RVA underestimates hydrological alterations because it neglects the alteration of periodicity. Compared with the traditional RVA and its alternatives, the revised RVA could give a more comprehensive representation of hydrological alteration caused by human and nature impacts. Thus, better protection of an ecosystem could be obtained by applying this method in the evaluation and management of water resources. Copyright © 2013 John Wiley & Sons, Ltd.     

Comments on the European Macroseismic Scale (EMS-98) in Terms of Its Applicability in Russia

A search for technogenic effects in the time series of earthquakes in Greece is carried out. The ine- quality of intra-week distributions of earthquakes including the events of M ≥ 3.7 is shown. Sharp changes in the pattern of Rayleigh-Schuster’s hodograph for the diurnal periodicity of earthquakes were revealed. They are located in the time vicinity of the moments of the equinox. The result supports the idea of the natural gen- esis of the diurnal periodicity of earthquakes and the important role of the Sun.     

Effects of geomagnetic disturbances in power spectra of atmospheric waves in the dynamo region of the ionosphere

The dynamics of wave disturbances in the ionospheric E region in the band of periods of thermal tidal waves and waves of planetary scales (T = 48, 72, and 192 h) has been studied based on the variations in the horizontal component of the geomagnetic field, observed at Paratunka and Barrow observatories in September–October 1999. It has been found that, at midlatitudes during high geomagnetic activity, the intensity of oscillations in the power spectra with T = 24 and 12 h varies with a periodicity of 16 days different from the periodicity of changes in the ΣKp index. The maximal deviations of these periods from the values under quiet conditions coincide with the maximal changes in the ΣKp index. The variations in the 48–192 h band of periods (especially with T ～192 h) intensify simultaneously with increasing geomagnetic activity. The intensity of this harmonic is several times as high as that of the harmonic with T ～ 24 h. The periodicity of changes in the harmonics intensity within the 48–192 h band coincides with the periodicity of changes in the ΣKp index. In the polar ionosphere, the effect of high geomagnetic activity is observed as an increase in the variations with a quasi-period of T ～ 24 h and as an appearance of variations in the 48–192 h band with the periodicity coinciding with the maximums in the ΣKp index variations.     

Preliminary study on enamel microstructure of Yuanmou Miocene hominoids of China

Late Miocene hominoid fossils found in Yunnan Province, China are of great importance in exploring hominid origins and hominoid phylogeny, and in recent years palaeoanthropologists have been paying great attention to them. The Yuanmou hominoid site is on…     

On the dynamics and origin of the Pugachevo group of gas-water-lithoclast (“mud”) volcanoes on Sakhalin Island: Visual observations and orohydrography

Visual observations of the activities of three gas-water-lithoclast (“mud”) volcanoes in the Pugachevo group in the Makarov District of Sakhalin Island were used to analyze the dynamics of these volcanoes. Our analysis confirmed the previous inference that a multirank periodicity is present in the eruptions of the volcanoes, with the periodicity being comparatively frequent and low in magnitude for the eruptions (every 1–2 years) at the Glavnyi or Central volcano and a very long but violent (every 65–70 years) at all the three volcanoes. Comparison of this periodicity with a similar periodicity observed in natural seismicity in the adjacent, highly seismic Uglegorsk District shows that the two phenomena are relatively independent. The natural seismicity in the form of large earthquakes is superimposed upon the gas-water-lithoclast volcanism mostly to serve as a trigger. The high-rank periodicity of 65–70 years noted above may be related to 11–22-year cycles of solar activity. Analysis of the orohydrographic setting in the area shows that the location of the present low-lying basin with volcanoes inside was formerly occupied by a dome uplift with a major gas field that controlled the generation of these volcanoes; it continues to drive their activity, causing a continued gradual subsidence or collapse of the deep basin with volcanoes, thus providing evidence of the high gas potential in the area of study.     

Maximum Entropy Spectral Analysis of the geological time series of the oxygen isotope record from deep-sea cores

A Maximum Entropy Spectral Analysis of the geological time series of the oxygen isotope 18 for the last 782,000 years showed 98,000 years as the most prominent periodicity, followed by 40,000 years of less than half the amplitude and still smaller peaks at 24,000, 67,000, 84,000, 107,000 and 786,000 years. Among the astronomical parameters, only eccentricity showed a similar periodicity viz. 96,000 years. Obliquity had a prominent periodicity at 41,000 years which was reflected in the oxygen isotope series also. Corresponding to the bimodal precession peaks (23,000 and 19,000 years), the oxygen isotope series showed a peak at 24,000 years and smaller peaks at 22,000 and 19,000 years. Our results compare well with those obtained byThomson (1990) with a more sophisticated method.     

大地震的18.6年周期

将全球分为15个研究区,用1900~2009年M_W≥7.0地震目录,统计分析了各区大地震与月球交点运动周期的关系,得出15个研究区中有10个区,大地震存在统计意义上的18.6 a周期:活跃段为12.4 a,平静段为6.2 a;环太平洋地震带北、南、西、东4大区的大地震,不仅有这样的周期,而且其地震活跃段的时间存在一定规律.用第6个18.6 a(1991~2009年)期间的大地震,检验据前5个18.6 a(1900~1990年)地震目录所得18.6 a 周期的稳定性和实用性,发现有这种周期的地区多数的周期性是稳定的.大地震18.6 a周期的可能成因有: (1)18.6 a潮波通过调制日潮和半日潮调制大地震; (2)上地幔内流体的潮汐(地内潮)作用; (3)18.6 a潮波通过影响地球自转变化调制大地震.