Fractal characteristics of the ground-observed ULF emissions in relation to geomagnetic and seismic activities

Results of fractal analysis of ultra-low-frequency (ULF) emissions registered at a low-latitude observatory, Guam (geomagnetic coordinates Φ_m=9°N, Λ_m=225°), and at a high-latitude drifting station, North Pole-30 (Φ_m=75°N, Λ_m=172°), are presented. The first set of data covers a long period of observations (20 months) including the strong (Ms=8) Guam earthquake of 8 August 1993. The second set of data covers a short period of observations (21 days) in April 1989 during the preparation phase of the big magnetic storm of 25 April 1989. Definite peculiarities in the behavior of ULF emission scaling (fractal) characteristics have been found, which are discussed on the basis of the self-organized criticality concept. The principal common peculiarity for magnetosphere–ionosphere and lithosphere systems is detection of flicker noise (β∼1, D₀∼2) in a certain frequency range on the preparation phase of strong magnetospheric and seismic events.     

Comparisons of Snowfall Measurements in Complex Terrain Made During the 2010 Winter Olympics in Vancouver

Solid precipitation (SP) intensity ( $ R_{\text{s}} $ ) using four automatic gauges, Pluvio, PARSIVEL (PArticle, SIze and VELocity), FD12P and POSS, and radar reflectivity factor ( $ Z $ ) using the POSS and PARSIVEL were measured at a naturally sheltered station (VOA) located at high level (1,640 m) on the Whistler Mountain in British Colombia, Canada. The R _s and other standard meteorological parameters were collected from March 2009, and from November 2009, to February 2010. The wind speed (ws) measured during this period ranged from 0 to 4.5 ms^?1, with a mean value of 0.5 ms^?1. The temperature varied from 4 to ?17 °C. The SP amount reported by the PARSIVEL was higher than that reported by the Pluvio by more than a factor of 2, while the FD12P and POSS measured relatively smaller amounts, but much closer to that reported by the Pluvio and manual measurements. The dependence of R _s from the PARSIVEL on wind speed was examined, but no significant dependence was found. The PARSIVEL’s precipitation retrieval algorithm was modified and tested using three different snow density size relationships (ρ _s–D) reported in literature. It was found that after modification of the algorithm, the derived R _s amounts using the raw data agreed reasonably well with the Pluvio. Statistical analysis shows that more than 95 % of $ Z_{{h_{\text{poss}} }} $ data measured by POSS appears to correlates well with the reflectivity factors determined using the three ρ _s–D relationships. The automated Pluvio accumulation and manually determined daily SP amount (SPm) measured during five winter months were compared. The mean ratio (MR) and the mean difference (MD), and the correlation coefficient (r) calculated using the data collected using the two methods, were found to be 0.96, 0.4 and 0.6 respectively, indicating respectable agreement between these two methods, with only the Pluvio underestimating the amount by about 4 %.     

Possible causes of the variation in fractal dimension of the perimeter during the tropical cyclone Dan motion

We calculated the fractal dimensions Db of the perimeter of tropical cyclone(TC)Dan based on the satellite GMS-5 infrared sensor images from 1800 UTC,1 October 1999 to 1200 UTC,9 October 1999.The fractal dimensions Db were used to characterize objectively the temporal change of TC complex structure.Our results show that the change of fractal dimension during TC Dan motion can be divided into three stages.The statistically significant difference does not exist either between Dm1 and DL or between Dm3 and DL,but it exists between Dm2 and DL,where Dmi denotes the mean value of Db in i-th stage(i=1,2 and3);DL denotes Lovejoy’s fractal dimension calculated based on satellite and radar data within the size range(1–1.2×106 km2),which is used as a"normal value"of the fractal dimension of the cumulus cloud perimeter for the global tropical region.TC Dan turns to the north from the west abruptly at the end of the second stage.The emergence of the second stage with high fractal dimensions may be viewed as a possible premonition for the track turning.Our results also show that there are two kinds of processes resulting in the translation from the first stage to the second stage.One is the interaction of TC circulation and an adjacent small scale convective cloud cluster,causing to the complexity increase of a local segment of the perimeter.The other includes the fragmentation of a strong convective area within the TC inner region,the self-organization of the small strong convective cloud clusters,the emergence,development,and merger of the small scale non-convective holes,and the formation of a gap of the perimeter,causing to the complexity increase of the whole TC perimeter.     

The origin mechanism of coalbed methane in the eastern edge of Ordos Basin

In the eastern edge of the Ordos Basin, the coalbed methane (CBM) development has not made substantial progress in the past 20 years, and the origin of gas can be used to guide the CBM block-selecting and development. Based on the 37 sets of carbon isotope data, the origin of the gas was determined and the origin mechanism was studied in this work. The δ ¹³C_PDB of methane ranges from ?70.5‰ to ?36.19‰ in the eastern edge in the Ordos Basin and the value becomes heavier from the north to the south. The secondary biogenic gas and the thermogenic gas are mixed in the shallow area and the thermogenic gas occurs in the medium and deep levels. The phenomenon is controlled mainly by the distribution of coal rank and hydrodynamics. Firstly, based on the relationship between China coal rank and methane δ ¹³C_PDB, the medium rank coal is dominant in the eastern edge of the Ordos Basin, and the mixture of the secondary biogenic gas and the thermogenic gas is formed in the coal of vitrinite reflectant ratio (R _max) between 0.5% and 2.0% if there is appropriate hydrodynamics; at the same time, because of the shallow burial depth, and the well-developed coal outcrop, meteoric water and other surface water carrying bacteria recharge the coal reservoir, metabolize the organic compounds at a relatively low temperature, and generate methane and carbon dioxide. Wherever the trapping mechanisms occur in the coal, such as Liulin and Hancheng, modern gas content should be high.     

Analysis of quality factors for Rayleigh channel waves

To facilitate investigation of the effect of imperfect elastic dissipation on thepropagation of Rayleigh-type channel waves and use of their quality factors in investigationsof the properties of coal seams, a simple method for calculating the quality factor QR isproposed in this paper. Introduction of complex velocities into the dispersion function allowscalculation of the dispersion function of Rayleigh-type channel waves in coal seams. By thecontrol variable method, we analyzed changes in QR with changes in coal seam thickness andP- and S-wave Q-factors within the coal seam and adjacent rock layers. The numerical resultsshow that the trend of the QR curve is consistent with the group velocity curve. The minimumQR value occurs at the Airy phase frequency; the Airy phase frequency decreases as coal seamthickness increases. The value of QR increases with increasing Qs2 （quality factor for S wavein coal seam）. We can compensate for the absorption of Rayleigh-type channel waves usingthe computed QR curve. Inversion of the QR curve can also be used to predict the thicknessesand litholoeies of coal seams.     

Pan evaporation modelling and changing attribution analysis on the Tibetan Plateau (1970–2012)

Pan evaporation (E_p) is an important indicator of water and energy and the decline of E_p has been reported in many regions over the last decades. The climate and E_p are dependent on each other. In this study, the temporal trends of E_p and main E_p drivers, namely mean air temperature (T_a), wind speed (u), global solar radiation (R_s), net long‐wave radiation(R_nl) and vapour pressure deficit (D) from 1970 to 2012, were calculated on the basis of 26 meteorological stations on the Tibetan Plateau. The arithmetic average of E_p from 26 stations decreased with the rate of ?11.91 mm a^?2; the trends of R_s, R_nl, T_a, u and D were ?1.434 w m^?2 decade^?1, 0.2511 w m^?2 decade^?1, 0.3590°C decade^?1, ?0.2376 m s^?1 decade^?1 and 9.523 Pa decade^?1, respectively. The diffuse irradiance is an essential parameter to model E_p and quantify the contribution of climatic factors to changing E_p. 60 724 observations of R_s and diffuse solar irradiance (R_d) from seven of the 26 stations were used to develop the correlation between the diffuse fraction (R_d/R_s), and the clearness index (R_s/R_o). On the basis of the estimation of the diffuse component of R_s and climatic data, we modified the PenPan model to estimate Chinese micro‐pan evaporation (E_p) and assess the attribution of E_p dynamics using partial derivatives. The results showed that there was a good agreement between the observed and calculated daily E_p values. The observed decrease in E_p was mostly due to declining wind speed (?13.7 mm a^?2) with some contributions from decreasing solar irradiance (?3.1 mm a^?2); and the increase of temperature had a large positive effect (4.55 mm a^?2) in total whilst the increase of R_nl had insignificant effect (0.35 mm a^?2) on E_p rates. The change of E_p is the net result of all the climatic variables. Copyright © 2014 John Wiley & Sons, Ltd.     

Paleomagnetic results from Late Carboniferous to Early Permian rocks in the northern Qiangtang terrane,Tibet, China,and their tectonic implications

Results of a systematic paleomagnetic study are reported based on Late Carboniferous to Early Permian sedimentary rocks on the north slope of the Tanggula Mountains,in the northern Qiangtang terrane(NQT),Tibet,China.Data revealed that magnetic minerals in limestone samples from the Zarigen Formation(CP^z)are primarily composed of magnetite,while those in sandstone samples from the Nuoribagaribao Formation(Pnr)are dominated by hematite alone,or hematite and magnetite in combination.Progressive thermal,or alternating field,demagnetization allowed us to isolate a stable high temperature component(HTC)in 127 specimens from 16 sites which successfully passed the conglomerate test,consistent with primary remnance.The tilt-corrected mean direction for Late Carboniferous to Early Permian rocks in the northern Qiangtang terrane is D_s=30.2°,I_s=-40.9°,k_s=269.0,a_(95)=2.3°,N=16,which yields a corresponding paleomagnetic pole at 25.7°N,241.5°E(dp/dm=2.8°/1.7°),and a paleolatitude of 23.4°S.Our results,together with previously reported paleomagnetic data,indicate that:(1)the NQT in Tibet,China,was located at a low latitude in the southern hemisphere,and may have belonged to the northern margin of Gondwana during the Late Carboniferous to Early Permian;(2)the Paleo-Tethys Ocean was large during the Late Carboniferous to Early Permian,and(3)the NQT subsequently moved rapidly northwards,perhaps related to the fact that the Paleo-Tethys Ocean was rapidly contracting from the Late Permian to Late Triassic while the Bangong Lake-Nujiang Ocean,the northern branch of the Neo-Tethys Ocean,expanded rapidly during this time.     

Fractal characterization and frequency properties of near-fault ground motions

This study explores the irregularity and complexity of strong earthquake ground motions from the perspective of fractal geometry, and constructs a relation with the frequency content of the ground motions. The box-counting fractal dimensions and five representative period parameters of near-fault ground motions from the Chi-Chi and Northridge earthquakes are calculated and compared. Numerical results indicate that the acceleration and velocity time histories of ground motions present the statistical fractal property, and the dominant pulses of near-fault ground motions have a significant influence on their box dimensions and periods. Further, the average box dimension of near-fault impulsive ground motions is smaller, and their irregular degree of wave forms is lower. Moreover, the box dimensions of ground motions reflect their frequency properties to a large extent, and can be regarded as an alternative indicator to represent their frequency content. Finally, the box dimension D of the acceleration histories shows a considerably negative correlation with the mean period T. Meanwhile, the box dimension of the velocity histories Dye is negatively correlated with the characteristic period T and improved characteristic period Tgi.     

Pore geometry of sandstone derived from pulsed field gradient NMR

Several parameters of pore geometry are needed for estimating permeability which is a key parameter for the characterization of reservoir sandstones. Powerful techniques for probing the pore space are the self-diffusion and the relaxation time NMR methods. However, the quality of results depends on the petrophysical model which underlies the interpretation of measurements. We applied the pulsed field gradient nuclear magnetic resonance (PFG-NMR) technique and measured time-dependent self-diffusion coefficients, D(Δ), of water in anhydrite cemented sandstones with low porosity and high tortuosity. The conventional method of fitting data with a function (Padé approximation) of the surface-to-volume ratio and the tortuosity yielded uncertain results. As part of a novel approach, we developed a numerical simulation code based on physical principles and a fractal pore space model. We compared our method with the Padé approximation and tested with data from the literature. For porous media with low tortuosity values and simple geometry such as randomly packed glass beads, both methods are in good agreement and give similar results. In sedimentary rocks, however, the new method of calculation is able to determine more accurate details of the pore geometry. However, its main advantage occurs in porous media with fractal geometry or with constricted pores, where the D(Δ)/D₀ curves deviate from the characteristic shape that is found for randomly packed glass beads.     

Earthquake parameters and spatial distribution of coseismic effects in Southern Siberia and Mongolia

In this work we review earthquakes that happened in Southern Siberia and Mongolia within the coordinates of 42°–62° N and 80°–124° E and first propose relationships between earthquake parameters (a surface-wave earthquake magnitude M _s and an epicentral intensity(I ₀) based on the MSK-64 scale) and maximal distances from an earthquake epicenter (R _{e max}), hypocenter (R _{h max}), and a seismogenic fault (R _{f max}) to the localities of secondary coseismic effects. Special attention was paid to the study of these relationships for the effects of soil liquefaction. Hence, it was shown that secondary deformations from an earthquake were distributed in space away from an earthquake epicenter, than from an associating seismogenic fault. The effects of soil liquefaction are manifested by several times closer to a seismogenic fault, than all other effects, regardless of the type of tectonic movement in a seismic focus. Within the 40 km zone from an earthquake epicenter 44% of the known manifestations of liquefaction process occurred; within the 40 km zone from a seismogenic fault—90%. We propose the next relationship for effects of soil liquefaction: M _s = 0.007 × R _{e max} + 5.168 that increases the limits of the maximum epicentral distance at an earthquake magnitude of 5.2 ≤ M _s ≤ 8.1 as compared to the corresponding relationships for different regions of the world.     

Author index volume 40

Tracer diffusion coefficients for Li in glasses of albite, orthoclase, and obsidian composition have been determined by a method involving deposition of a thin source on polished glass wafers, anneal under controlled temperature conditions (300–900°C), and ion-microprobe determination of the concentration profile. All results conform to an Arrhenius-type relationship,D = D₀exp(?Q/RT), whereQ is 23, 17, and 22 kcal mol^?1;D₀ is 0.2, 0.003, and 0.03 cm²s^?1 for albite and orthoclase glasses, and obsidian respectively. Lithium is thus a fast diffusing ion and behaves similarly to sodium in the same glasses. A mechanism involving jumps of the diffusing ions through oxygen hexagonal rings is suggested by consideration of ionic radii ratio of alkali (H, Li, Na, K, Rb, and Cs) ions to the oxygen anions.     

The degree of metamorphism of organic matter in sedimentary rocks as a paleo-geothermometer,applied to the Upper Rhine Graben

The subsidence of sedimentary layers implies increasing temperature downwards within the sedimentary column, so that the degree of coalification of organic matter increases continually. Apart from temperature, the slowly reacting chemical compounds of the organic matter strongly depend on time, too.It is shown that the coal rank is proportional to the integral of temperature and time of burial (t) for the Tertiary sedimentary rocks of the Upper Rhine Graben. This relationship is used to calculate paleogeothermal gradients (gradT) for some boreholes in the Upper Rhine Graben, from which the rate of burial during geological history (z(t)) is known. The degree of coalification is measured by its mean optical reflectivity (R _m), so that the relationship between coalification and geothermal history isR _m ² gradT z(t) dt.The results show high heat flow during Lower Tertiary and a decrease during Upper Tertiary at some locations of the Upper Rhine Graben. The recent high heat flow is not detectable in coalification. The young thermal anomaly is perhaps caused by ascending pore fluid and/or by heat conduction from a heat source in the lower crust.     

Absolute18O content of standard mean ocean water

The absolute values of the¹⁸O/¹⁶O ratio (R_s) and the relative¹⁸O content (X_s) in SMOW have been determined by comparing SMOW mass spectrometrically with well-defined synthetic mixtures of pure D₂¹⁸O and H₂¹⁶O. The results are:R_S = (2005.20 ± 0.45) × 10^?6, X_S = (2000.45 ± 0.45) × 10^?6     

Thermal diffusivity of rhyolitic glasses and melts: effects of temperature, crystals and dissolved water

Thermal diffusivity (D) was measured using laser-flash analysis on pristine and remelted obsidian samples from Mono Craters, California. These high-silica rhyolites contain between 0.013 and 1.10?wt% H₂O and 0 to 2?vol% crystallites. At room temperature, D _glass varies from 0.63 to 0.68?mm²?s^?1, with more crystalline samples having higher D. As T increases, D _glass decreases, approaching a constant value of ??0.55?mm²?s^?1 near 700?K. The glass data are fit with a simple model as an exponential function of temperature and a linear function of crystallinity. Dissolved water contents up to 1.1?wt% have no statistically significant effect on the thermal diffusivity of the glass. Upon crossing the glass transition, D decreases rapidly near ??1,000?K for the hydrous melts and ??1,200?K for anhydrous melts. Rhyolitic melts have a D _melt of ??0.51?mm²?s^?1. Thermal conductivity (k?=?D·??·C _P) of rhyolitic glass and melt increases slightly with T because heat capacity (C _P) increases with T more strongly than density (??) and D decrease. The thermal conductivity of rhyolitic melts is ??1.5?W?m^?1?K^?1, and should vary little over the likely range of magmatic temperatures and water contents. These values of D and k are similar to those of major crustal rock types and granitic protoliths at magmatic temperatures, suggesting that changes in thermal properties accompanying partial melting of the crust should be relatively minor. Numerical models of shallow rhyolite intrusions indicate that the key difference in thermal history between bodies that quench to obsidian, and those that crystallize, results from the release of latent heat of crystallization. Latent heat release enables bodies that crystallize to remain at high temperatures for much longer times and cool more slowly than glassy bodies. The time to solidification is similar in both cases, however, because solidification requires cooling through the glass transition in the first case, and cooling only to the solidus in the second.     

Fractal analysis of space-time variations in the epicentral field of earthquakes for several areas in the Baikal Rift Zone

Fractal analysis techniques were used to study space-time variations in the epicentral field of earthquakes for several areas in the Baikal Rift Zone (BRZ). In each area the epicentral field is found to be a system consisting of several subsystems in the shape of maxima of increased fractal dimension D _s , which occurred approximately at the same locations with constant or variable periodicity. We detected simultaneity and migration in the appearance of some maxima of D _s . Most local areas in the regions under study typically have an unformed type of epicentral field, to use A.V. Solonenko’s terminology, and this makes it difficult to predict the time of earthquake occurrence at a specified location using simple statistical methods. We used the variations in D _s in different regions to study the behavior of the present-day seismotectonic process in the BRZ as a whole.     

Clustering properties of Etna seismicity during 1981–1991

Space and time clustering properties ofseismic activity, affecting Etna Volcano (Italy)during 1981–1991, are investigated by fractaldimension analysis. Very interesting volcanic andseismic activity occurred within this time interval.Temporal evolution of the time fractal dimension D _t calculated on a moving window, revealscorrelation with the eruptive processes at differenttime scales confirming results obtained for a differenttime span (De Rubeis et al., 1997). Spatial fractaldimension D _s shows to be negativelycorrelated with the time fractal dimension D _t, suggesting a peculiar dynamic patternassociated with volcanic processes.     

海原断层系的分形研究

本文根据Okubo等人测量圣安德烈斯断层系所用的复盖维数法,对海原断层系进行了分形测量,求出海原断层系的整体维数D_0=1.137,其景泰段D_0=1.109,海原段D_0=1.182。计算中未得到邵家水段和李使堡段的分维数。此外,文中还着重探讨了断层几何与地震活动性及其力学环境的关系,进一步证明了自相似断层的几何复杂性与地震活动密切相关,剪切断裂带具较低分维数(1.1—1.3),而在张性环境中形成的断裂体系具较高的分维数(1.5—1.6)。最后本文讨论了断层迹线图等因素对分形测量精度的影响。     

Chaotic behaviour of acoustic emission induced in hard coal by gas sorption-desorption

This paper presents study of non-linear dynamics of acoustic emission (AE) generated in coal samples subjected to gas sorption-desorption. Carbon-dioxide and methane were used as sorbats. Experimental facilities used in high pressure sorption of CO₂ and/or CH₄ on coal comprised a pressure vessel and associated pressurisation and monitoring systems. Tests were conducted on medium-rank coal obtained from the Upper Silesia Basin. Several approaches to the treatment of experimental results are proposed in order to detect and characterize deterministic chaos: (1) analysis of fractal/multifractal character of AE energy rate, using fractal generalised dimensions D _q (q); (2) analysis of temporal changes of AE energy rate and its fractal correlation dimension D ₂; and (3) evaluation of attractor dimension within the reconstructed phase space from experimental time series. It was shown that AE generated during CO₂ sorption on medium-rank coal is a more heterogeneous and lower dimensional process in comparison with AE induced by CO₂ desorption. Yet, the AE associated with desorption of CO₂ exhibits higher heterogeneity than the AE generated during desorption of CH₄. There are certain similarities between changes of D₂ during desorption of CO₂ as well desorption of CH₄. However, dynamics of these changes and character of time distributions of D₂ differ, depending on a sorbate. We do not know the precise reason for observed differences, but we presume that the carbon-dioxide molecules dissimilarity to methane molecules can account for them.     

Age estimation of the deposition of the cretaceous Upper Sandstones and a later remagnetization event,from Hirna area,SE Ethiopia

Outcrops of the Cretaceous Upper sandstone formation some 375 km to the East of Addis Ababa on the motor Highway to Harar was paleomagnetically investigated. About seventy core samples were collected at various stratigraphic levels from 250–300 meters thick sedimentary formation. After standard sample preparations in the laboratory the resulting specimens were subjected to routine paleomagnetic demagnetization protocol. In the first steps of demagnetizations process the recent and viscous magnetizations were removed by heating until a temperature of level of 300 °C. Further demagnetization of the samples resulted in the isolation of the final magnetization with stable line segments that is directed towards the origin, which is interpreted as Characteristic Remanent Magnetization (ChRM). Rock – magnetic experiments have identified goethite (αFeOOH), hematite (αFe₂O₃), detritial hematite, and magnetite as the magnetic mineral phases carrying the remanence. The ChRM identified resulted in an average value of (D_s = 0.5°, I_s = ?0.7°, α₉₅ = 4.3°, N = 34) for the red sandstones while an average value of (D_s = 335.8°, I_s = ?31.8°, α₉₅ = 4.7°, N = 14) for the limestone intercalations. The former ChRM in the red sandstone is determined to be secondary while the latter ChRM is known to be primary. Comparison of these directional results and their pole equivalents with the African plate Apparent Polar Wander Path curve established by Besse and Courtillot (2003) give ages of between 115–130 Million years for the limestone intercalation and ages of 30 million years for red sandstone unit. These are interpreted respectively as estimates of the age of deposition and a later remagnetization respectively.