Anomaly in high-frequency geoacoustic emission as a close earthquake precursor

One of the possible earthquake precursor mechanisms, namely, acoustic emission, is discussed. The phenomenon of acoustic emission consists in the emission of acoustic pulses due to the formation of microfaults and cracks that precede fracture of objects, rock collapse in mines, earthquakes, etc. By the example of the geoacoustic emission observation on the Kamchatka Peninsula in the area of the Avachinskaya Bay and by the analysis of anomalies of this emission that accompany major seismic events, it is shown that anomalous geoacoustic noise is generated by the stress produced in the medium prior to these events. The high-frequency range (4–11 kHz) is most informative for the observation of geoacoustic noise caused by the crack formation processes.     

Conditions under which a thermal instability arises in friction

We investigate the one-dimensional, stationary problem of the temperature distribution and rate of plastic deformation in a uniform material under the influence of friction on the surface. The temperature distribution in the material is found by numerically solving the nonlinear heat conduction equation taking into account heat released both at the surface and in the sample interior. We modeled the rate of plastic deformation as a power-law function of temperature. We observed a phenomenon in the solution that might be called a thermal instability wherein stable solution exist only for loads lighter than some critical load. The temperature and plastic deformation distribution have a macroscopic character, and cannot be explained by the formation of a thin, highly deformed surface layer that is usually observed experimentally.Institute of Strength and Materials Research Physics, Russian Academy of Sciences, Siberian Branch. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 23–27, February, 1994.     

Scaling and precursor motifs in earthquake networks

A measure of the correlation between two earthquakes is used to link events to their aftershocks, generating a growing network structure. In this framework one can quantify whether an aftershock is close or far, from main shocks of all magnitudes. We find that simple network motifs involving links to far aftershocks appear frequently before the three biggest earthquakes of the last 16 years in Southern California. Hence, networks could be useful to detect symptoms typically preceding major events.     

Shear instability in the subsurface layer of a material in friction

The shear instability in subsurface layers of a material in friction has been investigated. As the friction surface is approached, several characteristic regions can be distinguished in the bulk of the metal: the region of plastic deformation and texturing (I), the region of severe fragmentation (II), the region of turbulent flow (III), and the region of laminar flow (IV). Regions I and II can be referred to as regions of conventional plastic deformation, whereas regions III and IV correspond to regions of the development of shear instability of the Kelvin-Helmholtz type at the shear boundary. The possibility of implementing this phenomenon within the hydrodynamic approach has been evaluated.     

与地震预测预报有关的几个物理问题

文章简要介绍了与地震预测预报有关的几个物理问题,包括地震活动性问题、地球深部物质的物理性质及其变化问题、地球深部的流体问题、地震破裂问题、地球深部的形变和应力问题.这些问题的研究涉及当代物理学的一些前沿领域,唐山大地震后30年来有诸多重要进展.     

Way of detecting an electromagnetic earthquake precursor

A way of detecting an electromagnetic earthquake precursor is suggested. Detection is carried out with a device composed of a vertical electrical antenna and a toroidal magnetic antenna located on the Earth’s surface. It is shown that the detector is the most sensitive to the radiation of an electrical dipole inside the lithosphere that is oriented normally to the Earth’s surface. Such a pattern allows one to detect electromagnetic precursors by the method suggested.     

与地震预测预报有关的几个物理问题

文章简要介绍了与地震预测预报有关的几个物理问题,包括地震活动性问题、地球深部物质的物理性质及其变化问题、地球深部的流体问题、地震破裂问题、地球深部的形变和应力问题.这些问题的研究涉及当代物理学的一前沿领域.唐山大地震后30年来有诸多重要进展.     

Soil gas radon as an earthquake precursor: some considerations on data improvement

A data processing technique based on impulse responses from multivariable time series was applied to radon data. It was found that soil gas radon at 50 cm depth was affected more by meteorological parameters than at 100 cm depth. This fact together with the fact that the radon change at the latter depth was larger when an earthquake occurred, radon measurement at 100 cm depth was tested as an earthquake precursor. The result showed correlation between radon anomalies and earthquake events.     

寂静地震与地震预测的物理问题

寂静地震是指发生了缓慢的位错、但几乎不辐射地震波的“地震” .在目前的地震预测的物理学研究中 ,通常是通过计算历史上曾经发生过的地震所引起的应力变化 ,或者通过研究地震活动的统计性质或“图像动力学” ,来推测一个断层带上发生地震的危险性 .寂静地震的信息的缺失 ,形成了地震预测的物理学研究中的一个很大的“盲区” ,而在相当程度上 ,解决地震预测的物理问题的主要困难和可能的突破的希望 ,也许就在于此 .寂静地震的研究目前还很不深入 .关于寂静地震的性质 ,文章作者提出两个猜想 :(1)寂静地震的频度 ,满足类似于GR定律的幂律分布 ;(2 )最大的寂静地震的地震矩 ,与“可见”的最大地震的地震矩相当 .     

Analysis of friction and instability by the centre manifold theory for a non-linear sprag-slip model

This paper presents the research devoted to the study of instability phenomena in non-linear model with a constant brake friction coefficient. Indeed, the impact of unstable oscillations can be catastrophic. It can cause vehicle control problems and component degradation. Accordingly, complex stability analysis is required. This paper outlines stability analysis and centre manifold approach for studying instability problems. To put it more precisely, one considers brake vibrations and more specifically heavy trucks judder where the dynamic characteristics of the whole front axle assembly is concerned, even if the source of judder is located in the brake system. The modelling introduces the sprag-slip mechanism based on dynamic coupling due to buttressing. The non-linearity is expressed as a polynomial with quadratic and cubic terms. This model does not require the use of brake negative coefficient, in order to predict the instability phenomena. Finally, the centre manifold approach is used to obtain equations for the limit cycle amplitudes. The centre manifold theory allows the reduction of the number of equations of the original system in order to obtain a simplified system, without loosing the dynamics of the original system as well as the contributions of non-linear terms. The goal is the study of the stability analysis and the validation of the centre manifold approach for a complex non-linear model by comparing results obtained by solving the full system and by using the centre manifold approach. The brake friction coefficient is used as an unfolding parameter of the fundamental Hopf bifurcation point.     

Nonlinear friction as a mechanism of directed motion

A simple model (ratchet model) of occurrence of directed motion under the action of a zero-mean fluctuating force is proposed. The motion arises when the symmetry in the velocity space is violated by nonlinear friction. The mechanism of the directed motion is discussed qualitatively. Existence conditions of the motion are derived. The efficiency of conversion of the fluctuating random force to the directed motion is estimated.     

Bi-instability as a precursor to global mixed-mode chaos

Bi-instability, in contrast to bistability, is shown to generate unstable chaotic saddles prior to the onset of chaos. The theory and numerics are applied to a CO2 laser model with modulated losses where unstable pairs of saddles coexist, form heteroclinic connections, and allow mixing between local chaotic attractors to produce global mixed-mode chaos.     

Separation of an isotope as a precursor of a gamma-raylaser medium

The nuclear isomer ¹⁷⁸Hf^m2, expected to be the most promising candidate for the gamma-ray medium, is rather difficult to produce in large quantities. There are a few ways to create this isomer, such as the irradiation of ¹⁷⁹Hf with high-energy neutrons through the (n,2n) reaction, the irradiation of ¹⁷⁶Yb with high-energy α particles through the (α,2n) reaction, the irradiation of ¹⁸¹Ta with protons through the (p,2p2n) reaction. In some of these reaction schemes the isotopically pure target works better than the natural one from the viewpoint of spectroscopic purity, handling of radioactive materials and productivity. However, isotope separation of heavy elements for producing a precursor as a target material is difficult in terms of cost/effectiveness. The atomic vapor laser isotope separation (AVLIS) method is expected as the most efficient way compared with the normal electromagnetic separation method. This revised version was published online in August 2006 with corrections to the Cover Date.     

Evaluation of the Kushida Method of short-term earthquake prediction

Kushida and Kushida found that FM radio waves from stations at distances over-the-horizon are received before earthquakes. Based on this finding, since the mid-1990’s, the Kushidas have been practicing “Earthquake Precursor Detection Experiment”. The performance of the Kushida method during 2000–2003 has been evaluated by checking their predictions against the actual seismicity. During the period, there were 92 Kushida predictions mentioning the possibility of M ≥ 5.5 event, whereas there were 49 M ≥ 5.5 earthquakes in the Japanese region. If the criteria for successful prediction are set as: the errors in date is less than one day, epicentral position is roughly within specified area, and error in M is less than 0.5, the success rate was 20% and the alarm rate was 12%. If we relax the criteria to: the errors in dates within 10 days, epicenter within additional 100 km of specified area and the magnitude error less than 1.0, the success rate was 40% and the alarm rate was 27%. These rates may look insufficient for a practical prediction method. Considering, however, the fact that no other short-term prediction has ever been made in Japan so far it is a significant achievement. Moreover, it was found that in almost all failed predictions, meaningful signals were detected although the interpretations were incorrect. This indicates that the method is promising provided further investigation is carried out. The same evaluation at the M ≥ 6.0 level showed that the general performance was similar to the M ≥ 5.5 level, except that both success rate and alarm rate were lower at the M ≥ 6.0 level. If this unexpected finding is real, it might be inherent to the methodology using scattering of short-wave length radio waves as suggested by M. Hayakawa and may contain important information in understanding the earthquake physics and LAI-coupling. The results of the present study indicate strongly that the earthquake prediction research using anomalous transmission of VHF FM radio waves should be enhanced in parallel with complementary research in other frequency ranges.     

Simulation of the influence of ultrasonic in-plane oscillations on dry friction accounting for stick and creep

We consider a pair of bodies contacting on an elastic substrate; the distance between the bodies oscillates harmonically at a high frequency. If a horizontal force is applied to the bodies, macroscopic movement starts only after achieving some critical value, which we identify with the static friction force of the oscillating system. The dependence of the static friction force on the oscillation amplitude is simulated numerically using the method of reduction of dimensionality. Results of simulation are compared with experimental data.     

Moving average rules as a source of market instability

Despite the pervasiveness of the efficient markets paradigm in the academic finance literature, the use of various moving average (MA) trading rules remains popular with financial market practitioners. This paper proposes a stochastic dynamic financial market model in which demand for traded assets has both a fundamentalist and a chartist component. The chartist demand is governed by the difference between current price and a (long-run) MA. Our simulations show that the MA is a source of market instability, and the interaction of the MA and market noises can lead to the tendency for the market price to take long excursions away from the fundamental. The model reveals various market price phenomena, the coexistence of apparent market efficiency and a large chartist component, price resistance levels, long memory and skewness and kurtosis of returns.     

从非线性与统计物理多重角度探讨数值地震预测

在科技文献中,地震常被比喻为非线性动力学过程或统计物理中的相变过程。文章探讨了如何从非线性力学中的分岔理论以及统计物理内的朗道相变理论出发,从势磊穿越,临界涨落与临界慢化等多个角度来分析和了解地震发生的全过程。文章作者试图在这些非线性力学与统计物理的基础上,综合地震过程中在时间与空间上应出现的前兆,解释如何可能做出具有普适性的数值地震预测。     

从非线性与统计物理多重角度探讨数值地震预测

在科技文献中,地震常被比喻为非线性动力学过程或统计物理中的相变过程.文章探讨了如何从非线性力学中的分岔理论以及统计物理内的朗道相变理论出发,从势磊穿越,临界涨落与临界慢化等多个角度来分析和了解地震发生的全过程.文章作者试图在这些非线性力学与统计物理的基础上,综合地震过程中在时间与空间上应出现的前兆,解释如何可能做出具有普适性的数值地震预测.     

EAST上由垂直不稳定性引发破裂的分析与预测

从EAST 装置2016 年的放电实验中，选取了119 次等离子体破裂放电数据，分析诱发等离子体破裂的原因，发现约60%的破裂是由垂直不稳定性直接引起的，其破裂后将会产生更大的晕电流，从而产生更大的电磁应力损坏装置。对由垂直不稳定性引起的破裂(简称为VID)(72 次放电)进行了研究，建立了分别基于单变量(垂直位移)和两维变量(垂直位移、垂直位移增长率)的预测模型用于对VID 破裂的预测。离线测试表明，基于两维变量的预测模型可以在破裂发生前20ms 给出破裂预警信号，预测成功率达93%。