Dynamic evolution patterns of the degree of ground resistivity anisotropy and the seismogenic process

Following a new train of thinking, this paper has explored first the potential information in the ground resistivity data observed by the existing geoelectric observation system, investigated and proposed a new dimensionless geoelectric precursor factor, the degree of ground resistivity anisotropy, S, and studied the characteristics of dynamic evolution pattern of S during the seismogenic process. The results show that, during the seismogenic process, the degree of ground resistivity anisotropy (S) displays a process of 'normal' →'abnormal strengthening (amplitude, range)' →abnormal weakening' → 'earthquake occurrence'→ 'normal'. The earthquake would occur at the time when the S value has entered the late stage of strengthening and turns to weaken and in the gradient belt on the margin of S anomaly region. The dynamic evolution pattern of S reflects the changes of the tectonic stress field during the seismogenic process. Therefore, it would be possible to trace the process of earthquake generation and occurrence from the dynamic evolution pattern of S so as to service earthquake prediction.     

Sediment characteristics and wind-induced sediment dynamics in shallow Lake Markermeer, the Netherlands

In 2007/08, a study was undertaken on the sediment dynamics in shallow Lake Markermeer (the Netherlands). Firstly, sediment characteristics were determined at 49 sites in the lake. Parameters such as median grain size and loss on ignition showed a spatial as well as water depth related pattern, indicating wind-induced sediment transport. Highly significant correlations were found between all sediment parameters. Lake Markermeer sediment dynamics were investigated in a sediment trap field survey at two permanent stations in the lake. Sediment yields, virtually all coming from sediment resuspension, were significantly correlated with average wind speeds, though periods of extreme winds also played a role. Sediment resuspension rates for Lake Markermeer were high, viz. on average ca. 1,000 g m⁻² day⁻¹. The highly dynamic nature of Lake Markermeer sediments must be due to the overall shallowness of the lake, together with its large surface area (dynamic ratio = [√(area)]/[average depth] = 7.5); wind-induced waves and currents will impact most of the lake’s sediment bed. Indeed, near-bed currents can easily reach values >10 cm/s. Measurements of the thickness of the settled “mud” layer, as well as ¹³⁷Cs dating, showed that long-term deposition only takes place in the deeper SE area of the lake. Finally, lake sediment dynamics were investigated in preliminary laboratory experiments in a small “micro-flume”, applying increasing water currents onto five Lake Markermeer sediments. Sediment resuspension started off at 0.5–0.7 cm/s and showed a strongly exponential behaviour with respect to these currents.     

On the seismic regime network method

In this paper, based on the previous study of practical use of seismic regime windows and seismic regime belts, the problem of establishing a “seismic regime network” consisting of “windows” and “belts” is further posed and discussed according to the observed fact that many “windows” and “belts” make responses to one earthquake. For the convenience of usage, the “seismic regime network” is divided into two classes, the first class and the second one. The former can be used in tendency prediction for long-term seismic activity in a large area, the latter used in short-term prediction in a small area. In this paper, after briefly discussing the physical significance of “seismic regime network”, it is pointed out that this simple and easily used method can be used to observe and extract seismic precursory information from a large area before a great earthquake, thus it can provide a reliable basis for the analysis and judgement of seismic regime tendency in time and space. No doult, this method is of certain practical significance. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,13, 161–169, 1991. The English version of this paper is improved by Prof. Shaoxie Xu.     

Linear combinations of order statistics to estimate the quantiles of generalized pareto and extreme values distributions

 Ad hoc techniques for estimating the quantiles of the Generalized Pareto (GP) and the Generalized Extreme Values (GEV) distributions are introduced. The estimators proposed are based on new estimators of the position and the scale parameters recently introduced in the Literature. They provide valuable estimates of the quantiles of interest both when the shape parameter is known and when it is unknown (this latter case being of great relevance in practical applications). In addition, weakly-consistent estimators are introduced, whose calculation does not require the knowledge of any parameter. The procedures are tested on simulated data, and comparisons with other techniques are shown. The research was partially supported by Contract n. ENV4-CT97-0529 within the project “FRAMEWORK” of the European Community – D.G. XII. Grants by “Progetto Giovani Ricercatori” are also acknowledged.     

Complete process of rock failure and the complete course of seismogeny

Conclusion Based on the analysis about the law of deformation rate, the concepts of the deformation rate of precursor, and its stress drop, and the stress drop of instability are discussed. According to the obtained deformationu ₀ corresponding to the maximum stress, the unstable pointu ₁ and the stable pointu ₂ of equilibrium, the complete process of rock failure can be divided into four stages quantitatively, corresponding to “the steady stage I”, “the precursor stage II”, “the unstable stage III” and “the later stage IV” of rock failure respectively, which can be used to simulate the complete course of earthquake. This kind of similarity between the complete process of rock failure and the complete course of earthquake suggests clearly the direction to reveal the law being of universal significance for the simulation of the earthquake in the laboratory experiments. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,13, 517–521, 1991.     

Observation and analysis of geomagnetic abnormity associated with the Ms=5.7 Jiujiang-Ruichang earthquake

A three-component geomagnetic survey was carried out during the period from 2002 to 2004 in China including Jiujiang-Ruichang region. Comparing the ＂2005.0 surface spline model of China geomagnetic field＂ created on the basis of the survey data with the ＂1970.0 surface spline model of China geomagnetic field＂, we can see an obvious abnormity in the geomagnetic horizontal component within a range of about 100 km around the epicenter of the Ms=5.7 Jiujiang-Ruichang earthquake occurred on November 26, 2005. After the earthquake, we carded out a repeated geomagnetic survey at 21 stations in the Jiujiang-Ruichang region and created a corresponding ＂2005.0 partially revised surface spline model of China geomagnetic field＂. By comparing the above three models, analyzing the geomagnetic horizontal component at the profile in the Jiujiang-Ruichang region and quantitatively studying the geomagnetic data of every stations around the Ms=5.7 earthquake, we have obtained the geomagnetic abnormity associated with this earthquake. Then the geomagnetic abnormity and its relation with seismic activity are discussed in this paper.     

Randomization test and its application

In this paper, one of the distribution-free tests — randomization test, is briefly described. It doesn’t need any distribution assumption and its related parameter estimation and is applicable to random and nonrandom sample. Then it is used to the test of migration of strong earthquakes on the Xianshuihe Fault Belt and “immunity” of large earthquakes in the large northern reigon of China. The test results show that there is 98.7% confidence degree for the migration of strong earthqueks on the Xianshuihe Fault Belt and “immunity” of earthqueks withM _S⩾8 toM _S⩾7 is significant in the large northern region of China. The obtained test results and the test method itself have certain application in the practice. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,15, 484–489, 1993.     

Spatial and temporal characteristics of acoustic emission activity during deformation of rock samples with inhomogeneous fault under biaxial compression

The spatial and temporal distributions of acoustic emission （AE） during the deformation of samples containing an inhomogeneous fault have been studied under biaxial compression. The results show that the fault strength and the duration from loading to failure increase and the failure mode changes from abrupt instability to gradual failure with increase of lateral stress σ2. The pre-setting fault and its heterogeneity play an important role in controlling AE spatial distribution during the deformation. The basic pattern of AE spatial distribution is controlled by the pre-setting fault, especially the parts with inhomogeneous strength and the strong segment, and the localization of fracturing starts from the positions with inhomogeneous strength, With increase of σ5, the dense AE distribution area spreads from the positions with inhomogeneous strength to the whole strong segment gradually. AE temporal sequence is significantly affected by σ2. The fault shows abrupt instability in final failure, which occurs on a background of ＂enhancement-quiescence＂ in microfracturing activity at lower σ2. At higher σ5, the fault shows gradual failure, and AE occurrence rate increases continuously and AER increase exponentially before and after the failure, The effect of σ2 on b-value is also remarkable, b-value shows precursory decrease in the weakening stage when fault behavior is abrupt instability, but it shows balanced change when fault behavior is gradual failure,     

Current horizontal strain field in Chinese mainland derived from GPS data

Introduction In the years when the reliable data could not be obtained and in the analysis of strain property and magnitude in history, the intensity, property and activity pattern of strain field were mainly inferred on the bases of geometric characters of surface traces and behaviors (especially the faults) as well as the characteristics of petrology (XIE, et al, 1993; Molnar, Tapponnier, 1975, 1977; Tapponnier, Molnar, 1977; FU, et al, 2000). However, they are the averaged results accumu…     

The middle-long term prediction of the February 3, 1996 Lijiang earthquake (MS=7) by the "criterion of activity in quiescence"

IntroductionIn the book Future CataS~ologr published in 1992, we proposed a viewpoiflt on using the"criterion of activity in quiescence" to predict big eathquake (MsZ7) (GUO, et al, 1992), and predicted in the book that in futore several years or in ten years a big earthquake (Ms27) will be possible to occur in the Zhongdian and nearby in Yunnan Province. In the 1994 nation-wide earthquake tendency consultation meeting we pointed out, once more, in the Zhongdian region of Yunnan Province…     

The pattern characteristics of the tendency variations of earth resistivity and its relation to earthquakes

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Features and physical process of the dynamic evolution pattern of ground resistivity precursor front

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Modeling non-stationary extreme waves using a point process approach and wavelets

In the present paper a statistical model for extreme value analysis is developed, considering seasonality. The model is applied to significant wave height data from the N. Aegean Sea. To build this model, a non-stationary point process is used, which incorporates apart from a time varying threshold and harmonic functions with a period of one year, a component μ _w(t) estimated through the wavelet transform. The wavelet transform has a dual role in the present study. It detects the significant “periodicities” of the signal by means of the wavelet global and scale-averaged power spectra and then is used to reconstruct the part of the time series, μ _w(t), represented by these significant features. A number of candidate models, which incorporate μ _w(t) in their location and scale parameters are tried. To avoid overparameterisation, an automatic model selection procedure based on the Akaike information criterion is carried out. The best obtained model is graphically evaluated by means of diagnostic plots. Finally, “aggregated” return levels with return periods of 20, 50 and 100 years, as well as time-dependent quantiles are estimated, combining the results of the wavelet analysis and the Poisson process model, identifying a significant reduction in return level estimation uncertainty, compared to more simple non-stationary models.     

A seismic index method for vulnerability assessment of existing frames: application to RC structures with wide beams in spain

A method for assessing the vulnerability of existing frames in terms of an energy-based seismic index is proposed. The ground motion is characterized by the so-called Seismic Hazard Energy Factor AE _I , and the susceptibility of the frame to damage is a function of two counterpart energy factors, AE _IS and AE _IU . AE _IS represents the level of the “maximum earthquake” that the frame can sustain within the elastic range. AE _IU characterizes the level of the “ultimate earthquake” associated with the collapse of the structure. The procedure takes into account the relation between the dynamic properties of the existing frame and the spectral shape of the ground motion expected at the site. The seismic index used by the method has a transparent and direct physical meaning; thus, it is useful not only for screening existing buildings but also to design a seismic retrofit solution, if needed. The method is applied to reinforced concrete frames with wide beam-column connections built in the southern part of Spain during the 1970’s, 1980’s and 1990’s.     

Analysis of cut-and-cover tunnels against large tectonic deformation

Tunnels are believed to be rather “insensitive” to earthquakes. Although a number of case histories seem to favor such an argument, failures and collapses of underground structures in the earthquakes of Kobe (1995), Düzce–Bolu (1999), and Taiwan (1999) have shown that there are exceptions to this “rule”. Among them: the case of tunnels crossed by fault rupture. This paper presents the analysis and design of two highway cut-and-cover tunnels in Greece against large tectonic dislocation from a normal fault. The analysis, conducted with finite elements, places particular emphasis on realistically modeling the tunnel-soil interface. Soil behavior is modeled thorough an elastoplastic constitutive model with isotropic strain softening, which has been extensively validated through successful predictions of centrifuge model tests. A primary conclusion emerging from the paper is that the design of cut-and-cover structures against large tectonic deformation is quite feasible. It is shown that the rupture path is strongly affected by the presence of the tunnel, leading to development of beneficial stress-relieving phenomena such as diversion, bifurcation, and diffusion. The tunnel may be subjected either to hogging deformation when the rupture emerges close to its hanging-wall edge, or to sagging deformation when the rupture is near its footwall edge. Paradoxically, the maximum stressing is not always attained with the maximum imposed dislocation. Therefore, the design should be performed on the basis of design envelopes of the internal forces, with respect to the location of the fault rupture and the magnitude of dislocation. Although this study was prompted by the needs of a specific project, the method of analysis, the design concepts, and many of the conclusions are sufficiently general to merit wider application.     

Two notes on the modern theory of inverse problems in geophysics

On the basis of comparison of the approaches to the solution of inverse problems in information theory and geophysics, it is shown that results, obtained in information theory, are suitable to supplement the theory of geophysical inverse problems. The conditions of the existence and uniqueness of the solutions of inverse problems in their practical discrete statement are specified. The terms of ɛ-entropy H _ɛ and informational capacity C _ɛ, characterizing “volumes” of unknown and observed data, are introduced. It is shown, that the instability of the solution of the inverse problem decreases with increase in H _ɛ, (increase in the “complexity” of studied section), if the relation H _ɛ ≤ C _ɛ is maintained.     

Study on the pattern and mode of vertical crustal deformation during the seismogenic process of intraplate strong earthquakes

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The 20-second regional magnitude <Emphasis Type="Italic">M</Emphasis><Subscript><Emphasis Type="Italic">S</Emphasis></Subscript>(20R) for the Russian Far East

A new modified magnitude scale M _S (20R) is elaborated. It permits us to extend the teleseismic magnitude scale M _S (20) to the regional epicenter distances. The data set used in this study contains digital records at 12 seismic stations of 392 earthquakes that occured in the northwest Pacific Ocean in the period of 1993–2008. The new scale is based on amplitudes of surface waves of a narrow range of the periods (16–25 s) close to the period of 20 s, for distances of 80–3000 km. The digital Butterworth filter is used for processing. On the basis of the found regional features concerning distance dependence for seismic wave attenuation, all the stations of the region have been subdivided into two groups, namely, “continental” and “island-arc.” For each group of stations, its own calibration function is proposed. Individual station corrections are used to compensate for the local features.     

Structural features of the subauroral ionosphere during the origination of the polarization jet

Narrow jets of rapid westward ion drifts were registered near the plasmapause projection at the F-region altitudes on the Cosmoc-184 satellite and were called “a polarization jet.” In this work, the effect of this polarization jet on the ionospheric structure has been studied, using a three-dimensional model of the high-latitude ionosphere, when strong local magnetospheric electric fields were originated. The calculations indicated that a narrow trough in the latitudinal variations in the electron density at the F-region maximum was formed in the zone where the electric field was switched on. This trough was more pronounced in the early evening hours, when the electron background density was still high, and was less distinct at low back-ground levels during premidnight hours. A comparison of the calculations and experimental data indicated that they were in good agreement with one another, which made it possible to state that the polarization jet was the main mechanism by which narrow electron density troughs were formed in the subauroral ionosphere.     

Bathing water quality monitoring of Varna Black Sea coastal zone,Bulgaria

Physicochemical and microbiological characteristics of the bathing waters in Varna’s Black Sea coastal area were investigated during year 2007 at 23 monitoring stations. Most of the determined physicochemical parameters—pH, mineral oils, surface active substances, phenols, dissolved oxygen, nutrients and microbiological parameters—“Total coliforms”, “Faecal coliforms”, “Faecal streptococci” were in compliance with the guidline’ limits and exhibited good water quality. Ammonium and phosphate’s pollution above the limits was determined at the South beach, Officers beach and Central beach situated in Varna’s central bathing zone. For the period of 13.08 to 24.10.2007—70% of the South beach samples analyzed for NH₄⁺ exceeded the limits 60 times and the concentrations of PO₄³⁻ exceeded the limits 17.5 times. Some deviations from the guidline’ limits regarding the microbiology were exhibited at the same beaches. A conclusion is made that the area of study is not yet seriously threatened, in spite of the rapid recreation during the last years.