A thermomagnetoelastic model of the earthquake source mechanism

Summary An explicit expression is derived for the body force, magnetic moment and heat source to be applied in the absence of a dislocation to produce a radiation pattern identical to that of a dislocation. These quantities depend only on the fault mechanism and the material properties of the medium in the immediate vicinity of the fault. The theory is developed for dislocations in an anisotropic inhomogeneous thermo-elastic medium that exhibits pyromagnetic and piezomagnetic properties. The magnetic moment equivalent, that completely describes the magnetical effects of the dislocation, is found to be dependent on the discontinuities of the disllacement prescribed across the fault, through the piezomagnetic coefficients. Discontinuities in the thermal field and its derivatives do not contribute to the magnetic moment equivalent, thus leading to the conclusion that pyromagnetism cannot produce magnetic effects.

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Russsunto Si ottiene l'espressione esplicita della forza di massa del momento magnetico e della sorgente di calore da applicare in assenza di una dislocazione che produca una radiazione identica a quella prodotta dalla dislocazione stessa. Queste grandezze dipendono solo dal meccanismo di faglia e dalle proprietà materiali del mezzo nelle immediate vicinanze della faglia. La teoria è sviluppata per dislocazioni in un mezzo termoelastico anisotropo e non omogeneo che esibisce proprietà piromagnetiche e piezomagnetiche. Si trova che il momento magnetico equivalente che descrive completamente gli effetti magnetici della dislocazione dipende dalla discontinuità dello spostamento prescritta sulla faglia, attraverso i coefficienti piezomagnetici. Le discontinuità nel campo termico e nelle sue derivate non contribuiscono al momento magnetico equivalente, portando così alla conclusione che il piromagnetismo non può produrre effetti magnetici.

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Резюме Выводится точное выражение для объемной силы, магнитного момента и теплового источника. Полученное выражение в отсутствии дислокаций применяется для образования диаграммы излучения, идентичной диаграмме с дислокацией. Эти величины зависят только от механизма повреждения и материальных свойств средЫ в непосредственной окрестности повреждения. Развивается теория дислокаций в анизотропной неоднородной термоупругой среде, которая обнаруживает пиро- и пьезомагнитные свойства. Обнаружено, что эквивалент магнитного момента, которЫй полностью описЫвает магинтнЫе эффектЫ дислокации, зависит от разрывов смещения, заданных на повреждении, через пьезомагнитные козффициенты. Разрывы в температурном поле и его производных не дают вклада в эквивалент магнитного момента, что приводит к утверждению, что пиромагнетизм не может вызывать магнитных эффектов.

     

A mechanism for radon decline prior to the 1978 Izu-Oshima-Kinkai earthquake in Japan

Precursory changes in the radon concentration of groundwater were observed by Wakita et al. (1980) prior to the 1978 Izu-Oshima-Kinkai earthquake of magnitude 7.0. Mechanisms for interpreting the anomalous radon decrease are examined in this paper. The SKE-1 well is situated in a volcanic-rock fractured aquifer of limited recharge. Given these geological conditions, the dilation of brittle rock mass occurred at a rate faster than the recharge of groundwater and gas saturation developed in newly created cracks preceding the earthquake. Radon volatilization into the gas phase can explain the anomalous decrease of radon precursory to the 1978 earthquake. To support the hypothesis, vapor–liquid two-phase radon-partitioning experiments were conducted at formation temperature (14 °C) using formation water from the SKE-1 well. Experimental data indicated that the decrease in radon concentration from 483 ± 3 count/min to 439 ± 7 count/min required a gas saturation of 2.35% developed in rock cracks through the dilatancy process.     

New evidence of earthquake precursory phenomena in the 17 January 1995 Kobe earthquake, Japan

Significant advances, both in the theoretical understanding of rupture processes in heterogeneous media and in the methodology for characterizing critical behavior, allows us to reanalyze the evidence for criticality and especially log-periodicity in the previously reported chemical anomalies that preceded the Kobe earthquake. The ion (Cl^-, K⁺, Mg⁺⁺, NO₃ ^- and SO₄ ^-) concentrations of ground-water issued from deep wells located near the epicenter of the 1995 Kobe earthquake are taken as proxies for the cumulative damage preceding the earthquake. Using both a parametric and non-parametric analysis, the five data sets are compared extensively to synthetic time series. The null-hypothesis that the patterns documented on these times series result from noise decorating a simple power law is rejected with a very high confidence level. Received 21 January 2000     

北京一次小震级地震前异常声-重力波产生机理的研究

观测到北京一次小震级地震(ML=3.0)前的异常声-重力波,并同时记录到异常地表倾斜信号。二者相关系数比较高,在接近震中的地区相关系数达到最大值0.5,相关系数随着远离震中的距离增大而减小。经过研究表明,异常声-重力波的产生与震前的地表缓慢活动引发的山体缓慢晃动导致的气流风速波动变化有关。基于350 m高的气象铁塔观测的风速数据,对两层大气模型传播的声-重力波进行了数值计算,得到的相对山体非平稳气流引起的声-重力波与观测信号在特征周期、幅度和速度三个参数上近似。以地表倾斜为例的模型与观测数据的一致性表明该震前声-重力波与地震存在关联性。     

Study on generation mechanism of anomalous acoustic-gravity waves before the 2011 Beijing earthquake(M_L=3.0)

Observation results of abnormal acoustic-gravity waves before a Beijing earthquake(M_L=3.0) are presented.During this period,abnormalities of earth surface tilt variations were also recorded.The cross-correlations between the both values are high,which reach maximal values of 0.5 in the area close to the epicenter.The correlations decrease with increasing distances from the epicenter.It was proposed that generation of the anomalous waves may be associated with the pressure and wind perturbations in the air flow caused by slowly shaking mountains during slow surface motion preceding the earthquake in Beijing.Based on the wind velocity data taken from a 350 m meteorological tower in Beijing,the propagation of ducted acoustic-gravity waves in a two-layer model of the atmosphere was numerically simulated.It is shown that characteristic periods,amplitudes and velocities of the simulated phases which were assumed from non-stationary air flow relative to mountains are approximate to the observed phases.A consistency between the simulated results and observation data indicates that a slow surface motion may be a possible source of the anomalous acoustic-gravity waves observed prior to the earthquake.     

On the mechanism of rhodamine 6G fluorescence quenching

The fluorescence of the widely used TPF dye rhodamine 6G is quenched by photons of the ruby as well as the Nd-glass laser. Taking into consideration the polarisation of the ground- and excited-state absorptions of rhodamine 6G a simple model of quenching results. The main process is an S₁ absorption with subsequent leave of the ordinary rhodamine 6G singlet system. For Nd-laser photons the cross section of the concerned transition following from our quenching experiments is σS₁→S₂ = 1.2×10^-16 cm².     

北京一次小震级地震前异常声-重力波产生机理的研究

观测到北京一次小震级地震(ML=3.0)前的异常声-重力波,并同时记录到异常地表倾斜信号。二者相关系数比较高,在接近震中的地区相关系数达到最大值0.5,相关系数随着远离震中的距离增大而减小。经过研究表明,异常声-重力波的产生与震前的地表缓慢活动引发的山体缓慢晃动导致的气流风速波动变化有关。基于350 m高的气象铁塔观测的风速数据,对两层大气模型传播的声-重力波进行了数值计算,得到的相对山体非平稳气流引起的声-重力波与观测信号在特征周期、幅度和速度三个参数上近似。以地表倾斜为例的模型与观测数据的一致性表明该震前声-重力波与地震存在关联性。      

Chromium isotopes tracking the resurgence of hexavalent chromium contamination in a past-contaminated area in the Friuli Venezia Giulia Region,northern Italy

The origin of a resurgent hexavalent chromium contamination in groundwater from a phreatic aquifer in the Friuli Venezia Giulia Region plain was investigated by chromium isotopic systematics. The area underwent a severe Cr(VI) contamination by industrial effluents in 1997, when Cr(VI) concentration in groundwater reached 4500?µg/L. In subsequent years the contamination naturally attenuated, totally disappearing in 2003. A renewal of water contamination was observed in 2008, Cr(VI) reaching 1560?µg/L. The δ⁵³Cr value in groundwater and extracts from sediments was measured in 2009–2011, and it ranges between ?3.21 and +0.21‰ and between ?4.71 and +1.26‰, respectively. Due to the lack of geogenic Cr-sources, these data are interpreted as evidence of the subsequent oxidation through Mn-oxides of the Cr(III) hosted in the aquifer and originated by the reduction of the original industrial chromates. Cr(III) is characterized by negative δ⁵³Cr, starting from the δ⁵³Cr value around zero of Cr(VI) in industrial effluents. Oxidation liberates soluble Cr(VI) which is transported by groundwater and permeated soils. The complex Cr-isotopic vs. concentration distribution reflects both the new Cr(VI) reduction and dilution processes in the aquifer system. From an environmental point of view, the data raise concerns regarding the potential impact of past Cr(VI)-contamination.     

On the mechanism of proton conductivity in H3OSbTeO6

Pyrochlore-type H₃OSbTeO₆ is a remarkable proton conductor exhibiting an outstanding electrical conductivity even at ambient temperature. It consists of a three-dimensional interconnected (Sb,Te)O₆ framework, built from randomly distributed corner-shared SbO₆ and TeO₆ octahedra, forming large cages in which the H₃O⁺ ions are located. The dynamics of the caged species has been investigated by temperature-dependent neutron diffraction, quasielastic neutron scattering, and NMR experiments. Three types of motion may be discerned, namely, stochastic rotations of the H₃O group around its 3-fold axis, jumps between four equivalent positions within the cage, and long-range inter-cage translational diffusion. The onset of ionic conductivity is clearly reflected by structural changes. Details of the complex diffusion mechanism are given.     

Deuteron exchange mechanism for the6Li(n, α) reaction at low energies

It is proposed that the major part of the low energy (l/v)⁶Li(n, α)³H cross section may be explained as being due to a direct deuteron exchange mechanism. This proposal is in agreement with recent experimental data on the spin-dependent⁶Li(n, α) cross section; it may be used to extract information on the⁶Li-αd vertex constant. The importance of the assumption of ad-exchange process for the⁶Li(n, α) angular distribution is discussed in the framework ofS-matrix theory.