On the relation of moderate-short term anomaly of earth resistivity to earthquake

1139 moderate-short term anomalies of earth resistivity before 196 earthquakes with magnitude M_s=3.2-7.9 (the Ms≥4.0 event accounting for 94%) are studied in this paper, the results are concluded as following: ①There is a nonlinear function between anomaly time and magnitude of earthquake. For earthquakes Ms≤5.0 or so anomaly time linearly increases quickly with magnitude increasing; for earthquakes 5.0<M_s<6.5 the increasing rate of the time with magnitude increasing gradually become small; for earthquakes M_≥6.5 the rate is quite small.②There is a nonlinear exponential function between anomaly amplitude and magnitude. For earthquakes Ms≤5.0 or so the amplitude increases slowly with the increasing of magnitude, for earthquakes 5.0<M_s<6.5 the increasing of the amplitude is gradually accelerated with magnitude increasing; for earthquakes M_s≥6.5 the increasing is accelerated quickly with magnitude increasing. The two non-linear functions mentioned above are interpreted qualitatively, and the mechanism of this phenomenon is discussed based on the model of rheomorphic medium.

Process of source dynamics of the Jingtai earthquake (M=6. 2 )

In this paper, the process of source dynamics of the Jingtai earthquake (M= 6. 2) is studied on the basis of both earth resistivity changes before the event and the spatial directivity of single-observatory magnitude measurements of the seismic network of China. The following conclusions are obtained: the NW-SE directional tension stress (or the one about in the direction) inside the source region was enhanced during the short period from three to five months before the event, and done still further about in twenty odd days before the event, so that it finally leads the fault in about the EW strike to produce dislocation in NWW-SEE direction. Finally, this dislocation pattern caused the strong ground vibration to be received at the seismic observatories which were located in the NWW and SEE directions of the epicenter, while the weak vibration to be received at the ones in NE and south directions of the epicenter. At last, understandings on the imminent earthquake prediction through earth resistivity method are set forth.

Character of geoelectric intermediate term precursory anomaly and judgment for intermediate term tendency of strong earthquake

Based on systematic processing to long-term geoelectric observation data, we mainly studied the character of earthresistivity tendency anomaly for MS>7.0 strong earthquakes and its relation with seismogenic process. The character of quick descending at early stage and then slow development with steady shape in geoelectricity is a basicfeature ofgeoelectric tendency anomaly for strong earthquake. Usually the ratio of average time between the earlyquick descend stage and the post slow development stage is about if4. In addition, for Tangshan Ms=7.8 andSongpan Ms=7.2 earthquake, we studied the diffusion character of the geoelectric tendency anomaly development.For Tangshan earthquake, we also studied the time-space-strength dynamic evolution character of its geoelectricprecursory information quantity. The results showed that diffusion velocity of geoelectric precursory tendencyanomaly for the two earthquakes is respectively 90 kmja and 100 km/a. The variation character of geoelectric tendency anomaly presents some indexes for judgment of strong earthquake tendency background and intermediateterm prediction.

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

Through systematically summarizing the observational data of earth resistivity during 26 years from nearly a hundred stations in China, the author found that the pattern of the earth resistivity (ρs) tendency variations,based on monthly average data, could be divided into five types, three types of which were defined as anomalous variation, which have different qualitative and quantitative characteristics and different relations with earthquakes as well.The first type of tendency variation called “funnel” is related to strong earthquakes, the Second type called “scoop” has good corresponding relation with moderate earthquakes, and the third type called “tilt” has no relation with earthquakes. Preliminary discussions about the relations between the three types of ρs tendency variation patterns and earthquakes are made in this paper, according to the experimental results of pressed rocks. It is concluded that the different patterns of ρs tendency variation actually reflect the different stress conditions of underground soil-rock layers: the “funnel” type reflects high stress status, the “scoop” type shows moderate stress condition and the “tilt” type is related to stress relief. All of such knowledges mentioned above are very useful in making accurate medium-term earthquake prediction.

3-D rheologic model of earthquake prepa-ration (III): Precursor field

On the basis of the theory of viscoelastic displacement and strain field for the three-dimensional rheologic model of earthquake preparation, this paper mainly studies the theoretical solution of precursor field for the three-dimensional rheologic model of earthquake preparation. We derive the viscoelastic analytical expressions of the ground tilt, underground water level, earth resistivity at an arbitrary point （x, y, z） in the rheologic medium, and analyzed the earth resistivity preliminarily, providing a certain theoretical basis for the precursor analysis of seismogenic process.

The mutation sequence of earth resistivity and earthquakes

Large amount of practically-observed iata were analyzed hased on the principles of fracture mechanics, and it was found that the mutation of earth resistivity was, to a certain extent, corrrelated with the rupture of media. Among the mutation sequences before most strong and moderate earthquakes had generally a relatively obvious maximum mutation. An approximately linear relation was found between the interval from starting of the maximum mutation to the occurrence of an earthquake and the magnitude and the epicentral distance of the earthquake. Furthermore, such a mutation showed a tendency to radiate from the epicenter to the peripheral areas. It is thus thought to be possible to use the mutation sequence to predict earthquakes. Finally, the paper also unfolds discussions on a number of practical problems in the earthquake prediction practice.

Preliminary Study on the Relationship between the M_s8.0 Wenchuan Earthquake of 2008 and the Anomalies of Earth Resistivity Observed at Qingdao Seismic Station

Near-surface earth resistivity and underground water level anomalies were recorded at Qingdao seismic observatory of Shandong Province before and after the MS8.0 Wenchuan Earthquake of May 12,2008.The observed data of earth resistivity at the observatory revealed that the underground water level dropped and the resistivity increased.It is postulated that in the special tectonic setting at Qingdao observatory,the variation of stress and strain caused the change of water level beneath the station,thus,leading to the variation of earth resistivity.The relationship between the variation of stress field and the change of earth resistivity before earthquake is analyzed.

Verification Protocols for the Lightning Protection of a Large Scale Scientific Instrument in Harsh Environments: A Case Study

This paper is devoted to the study of the most suitable protocols needed to verify the lightning protection and ground resistance quality in a large-scale scientific facility located on a site with high risk of lightning strikes. We illustrate this work by reviewing a case study: the largest telescopes of the Northern Hemisphere Cherenkov Telescope Array, CTA-N. This array hosts sensitive and high-speed optoelectronics instrumentation and sits on a clear, free from obstacle terrain at around 2400 m above sea level. The site offers a top-quality sky but also features challenging conditions for a lightning protection system: the terrain is volcanic and has electrical resistivities well above 1 kOhm·m. In addition, the environment often exhibits humidities well below 5%, and strong winds pose challenging conditions. On the other hand, the high complexity of a Cherenkov telescope structure does not allow a straightforward application of lightning protection standards. We describe here how the risk assessment of direct strike impacts was made and how contact voltages and ground system were both tested. Finite Element Simulation (COMSOL Multiphysics) has been used to estimate the current flowing through the parts of the earthing system designed for the telescopes in the case of a direct strike impact. This work is intended to provide assistance to scientists and managers involved in the construction of scientific installations, particularly those in charge of defining verifiable reliability and safety requirements for lightning protection.

Effect of Gum Arabic as Partial Replacement of Cement on the Durability Properties of Compressed Laterite Blocks

Compressed stabilized earth blocks are the innovation of building materials replacing the earth blocks commonly called adobe. Common stabilizers (cement and lime) have been found to be expensive and harmful to the environment. Finding a natural, available, environmentally friendly stabilizer is vital. The objective of this study was therefore to assess the effects of gum Arabic (GA) as binder on the durability properties of laterite blocks. Compressed laterite blocks were stabilized with 2% and 6% respectively as total percentage of binders in the blocks (cement and/or GA). The results showed that GA improved the abrasion and drop resistances of compressed blocks. It has been found that the abrasion resistance of compressed blocks increased with the increase of GA content and the decrease of cement content. For instance, the mass abraded away of blocks stabilized with cement only was reduced up to 95.18% when GA was used to partially replace cement. As for drop test, the higher the content of GA the higher the resistance of blocks to drop.

Discussion on Common Problems in Risk Assessment of Lightning Disaster

The problems in calculating parameters of equivalent collection area,earth resistivity and lightning protection category as well as their effects on lightning disaster risk assessment were analyzed,and practical examples proved the effects of those differences on lightning protection identification,intercept efficiency calculation in evaluating lightning disaster risk. In the meantime,several new concepts,such as the height of buildings for lightning protection were defined,and a fixed radius value was set to the ground flash density for calculation,establishing the ground flash density formula to solve the problems in parameter calculation,which would be beneficial to promote the standardization of lightning disaster risk assessment.

Synthesis and sintering of samarium rich SmS_x and its electrical property

Non-stoichiometric samarium monosulfide（SmS_x, 0.55≤x≤1.2） was synthesized from Sm_2S_3 and SmH_3 at 1273 K for 3 h under vacuum. The influence of reaction ratio of Sm_2S_3 to SmH_3 on the fabrication of SmS_x was investigated. The fabrication of SmS required the molar ratio of Sm_2S_3 to SmH_3 above 1. Lattice parameter of synthetic SmS_x increased firstly and then decreased to saturate following with the addition of SmH_3 content. SmS_x compact was sintered at 1373 K by spark plasma sintering. Density of synthetic SmS_x was about 99% of theory density. Seebeck coefficient of n-type semiconductor Sm Sx decreased as temperature rose. The absolute value was distributed between 170–280 μV/K. The electrical resistivity of SmS_x（0.86≤x≤1.07） decreased with temperature increasing and showed similar temperature dependence. The surplus Sm which randomly distributed in the SmS_x（0.55≤x≤0.75） matrix led to a remarked reduction of electrical resistivity. The optimized power factor for SmS_（0.6） and Sm S_（0.75） could reach 1500 μW/（K^2·m） at 600 K.

Comparison effects of lanthanum stearate and antioxidants in epoxidized natural rubber

This work studied possibilities of using lanthanum stearate（LaS t） as an antioxidant in epoxidized natural rubber containing 25 mol.% expoxidation（ENR25） compounds. For comparison purposes, two commercial antioxidant 4010 NA and MB were also used. The influence of LaS t, antioxidant 4010 NA and MB on cure characteristics, mechanical properties, crosslink density, hot air aging and thermo-oxidative degradation were studied. The results indicated that the incorporation of LaS t and antioxidants could accelerate the vulcanization of ENR. The ENR vulcanizates with antioxidant MB had better mechanical properties than 4010 NA and LaS t. Compared with antioxidant 4010 NA and MB, the ENR25 vulcanizates with the addition of LaS t exhibited the best hot air aging resistance and thermo-oxidative stability.