Coal facies evolution of the main minable coal-bed in the Heidaigou Mine,Jungar Coalfield,Inner Mongolia,northern China

The No. 6 Coal-bed from the Heidaigou Mine, Jungar Coalfield, Inner Mongolia is a super-large Ga deposit. The dominant carrier of Ga is boehmite in coal. The study of coal facies may provide genetic enrichment information of Ga and its carrier (boehmite) in the Ga deposit. On the basis of study on coal petrology and mineralogy, it was found that the No. 6 Coal-bed from the Heidaigou Mine of Jungar was enriched in inertinites and the microlitho-types were dominated by clarodurite. The maceral morphological features and association indicate that the coal-bed was formed in a dry sedimentary environment or in a periodic dry sedimentary environment caused by the alternating variations of groundwater level. The optimum conditions for the enrichment of Ga and its particular carrier (boehmite) were dominated by four transitional conditions: (1) the upper delta plain which was the transitional zone between alluvial and lower delta plains, (2) the transitional zone between the dry and wet forest swamps, being slightly apt to the dry one, (3) the transitional tree density between the thick and loose ones, and (4) the low moor that was the transitional zone between two high moors during peat accumulation.     

Ground motion characterization and seismic hazard assessment in Spain: context,problems and recent developments

This article points out some particular features conditioning seismic hazard assessments (SHA) in Spain, a region with low–moderate seismicity. Although sized earthquakes occurred in the past, as evidenced by historical documents and neotectonic studies, no large events occurred during the last decades. The absence of strong motion records corresponding to earthquakes with magnitude larger than 5.5 is an important obstacle for the development of ground motion models constrained by local data, with the consequent difficulty in SHA studies. In this paper, some recent developments aiming at providing solutions to these difficulties are presented. Specifically, a strong motion databank containing a massive collection of accelerograms and response spectra from different configurations source-path-site corresponding to earthquakes all over the world is introduced, together with software utilities for its management. A first application of this databank is the development of specific ground motion models for Spain and for the Mediterranean region that predict peak ground accelerations as a function of several definitions of magnitude, distance and soil class. The predictive power of these ground motion models is tested by contrasting their estimates with recently recorded ground motions. The comparison between our ground-motion models with others proposed in the literature for other areas reveals a regular overestimation of the expected ground motions at Spanish sites by the non-local models. Consequently, SHA studies based in external models may overestimate the predicted hazard at the Iberian sites. In the last part of the paper a method for checking whether the response spectra proposed in the Spanish Building Code (NCSE-02) are consistent with actual accelerometric data from recent low magnitude earthquakes is applied. The spectral shapes of the Spanish Building Code NCSE-02 are compared with the response spectral shapes deduced from the available accelerograms by normalising the response spectra with the recorded PGA. It is appreciated that the NCSE-02 spectral shapes are exceeded by a large number of actual spectral shapes for short periods (around 0.2 s), a result to be taken into account in further revisions of the NCSE-02 code. The issues tackled in this work constitute not only an improvement for ground-motion characterisation in Spain, but also provide guidelines of general interest for potential applications in other regions with similar seismicity.     

Ocean/ice shelf interaction in the southern Weddell Sea: results of a regional numerical helium/neon simulation

Ocean/ice interaction at the base of deep-drafted Antarctic ice shelves modifies the physical properties of inflowing shelf waters to become Ice Shelf Water (ISW). In contrast to the conditions at the atmosphere/ocean interface, the increased hydrostatic pressure at the glacial base causes gases embedded in the ice to dissolve completely after being released by melting. Helium and neon, with an extremely low solubility, are saturated in glacial meltwater by more than 1000%. At the continental slope in front of the large Antarctic caverns, ISW mixes with ambient waters to form different precursors of Antarctic Bottom Water. A regional ocean circulation model, which uses an explicit formulation of the ocean/ice shelf interaction to describe for the first time the input of noble gases to the Southern Ocean, is presented. The results reveal a long-term variability of the basal mass loss solely controlled by the interaction between waters of the continental shelf and the ice shelf cavern. Modeled helium and neon supersaturations from the Filchner–Ronne Ice Shelf front show a “low-pass” filtering of the inflowing signal due to cavern processes. On circumpolar scales, the simulated helium and neon distributions allow us to quantify the ISW contribution to bottom water, which spreads with the coastal current connecting the major formation sites in Ross and Weddell Seas.

North Pacific sea ice cover, a predictor for the Western North Pacific typhoon frequency?

The relationship between the sea ice cover in the North Pacific and the typhoon frequency has been studied in this paper. It follows that the index for the sea ice cover in the North Pacific (ISA) both in December-January-February (DJF) and in March-April-May (MAM) is negatively correlated with annual typhoon number over the western North Pacific (TNWNP) during 1965―2004, with correlation coeffi-cients of -0.42 and -0.49 respectively (above 99% significant level). Large sea ice cover in the North Pacific tends to decrease TNWNP. Positive ISA (MAM) is associated with the tropical circulation and SST anomalies in the North Pacific, which may lead to unfavorable dynamic and thermal conditions for typhoon genesis over WNP from June to October (JJASO). The variability of the atmospheric circula-tion over the North Pacific, associated with the ISA anomaly in MAM is connected to the tropical at-mospheric circulation variability in MAM via the teleconnection wave train. Besides, as the tropical circulation has strong seasonal persistency from the MAM to JJASO, thus, the ISA in MAM-related variability of the tropical atmospheric circulation as well as the SST can affect the typhoon activity over the western North Pacific.     

Experimental study of surface texture and resonance mechanism of booming sand

The sound-producing mechanism of booming sand has long been a pending problem in the blown sand physics. Based on the earlier researches, the authors collected some silent sand samples from Teng- ger Desert, Australian Desert, Kuwait Desert, beaches of Hainan Island and Japanese coast as well as the soundless booming sand samples from the Mingsha Mountain in Dunhuang to make washing ex- periments. In the meantime the chemical corrosion experiment of glass micro-spheres, surface coating experiment and SEM examination were also conducted. The experimental results show that the sound production of booming sand seems to have nothing to do with the presence of SiO2 gel on the surface of sand grains and unrelated to the surface chemical composition of sand grains but is related to the resonance cavities formed by porous (pit-like) physical structure resulting from a number of factors such as wind erosion, water erosion, chemical corrosion and SiO2 gel deposition, etc. Its resonance mechanism is similar to that of Hemholz resonance cavity. Under the action of external forces, nu- merous spherical and sand grains with smooth surface and porous surface are set in motion and rub with each other to produce extremely weak vibration sound and then become audible sound by human ears through the magnification of surface cavity resonance. However the booming sands may lose their resonance mechanism and become silent sand due to the damping action caused by the invasion of finer particles such as dust and clay into surface holes of sand grains. Therefore, clearing away fine pollutants on the quartz grain surface is an effective way to make silent sand emit audible sound.     

Town of Tornio in November 1898: a rare survey of earthquake damage in Finland

This study investigates the effects of the Fennoscandian earthquake that occurred on 4 November 1898 (GMT) on Tornio in Northern Finland. The extra fire inspection conducted in the town on 21, 22 and 23 November 1898 provided insight into the failures caused by this low-magnitude earthquake. The building stock was of timber with masonry stone components. More than 30 heating units sustained damage. The macroseismic intensity in Tornio is estimated at I = 6 (European Macroseismic Scale).     

Study on inelastic displacement ratio spectra for near-fault pulse-type ground motions

In displacement-based seismic design, inelastic displacement ratio spectra (IDRS) are particularly useful for estimating the maximum lateral inelastic displacement demand of a nonlinear SDOF system from the maximum elastic displacement demand of its counterpart linear elastic SDOF system. In this study, the characteristics of IDRS for near-fault pulse-type ground motions are investigated based on a great number of earthquake ground motions. The in? uence of site conditions, ratio of peak ground velocity (PGV) to peak ground acceleration (PGA), the PGV, and the maximum incremental velocity (MIV) on IDRS are also evaluated. The results indicate that the effect of near-fault ground motions on IDRS are signifi cant only at periods between 0.2 s - 1.5 s, where the amplifi cation can approach 20%. The PGV/PGA ratio has the most signifi cant in? uence on IDRS among the parameters considered. It is also found that site conditions only slightly affect the IDRS.     

Application of <Superscript>137</Superscript>Cs fingerprinting technique to interpreting sediment production records from reservoir deposits in a small catchment of the Hilly Loess Plateau,China

According to variations of 137Cs and clay contents, 44 flood couplets were identified in a profile of reservoir deposit with a vertical length of 28.12 m in the Yuntaishan Gully. Couplet 27 at the middle of the profile had the highest average 137Cs content of 12.65 Bq kg-1, which indicated the 1963s' deposits, then 137Cs content decreased both downward and upward in the profile. The second top and bottom couplets had average 137Cs contents of 2.15 Bq kg-1 and 0.92 Bq kg-1, respectively. By integrated analysis of reservoir construction and management history, variations of 137Cs contents over the profile, sediment yields of flood couplets and rainfall data during the period of 1958-1970, individual storms related to the flood couplets were identified. 44 floods with a total sediment yield of 2.36×104 m3 occurred and flood events in a year varied between 1 and 10 times during the period of 1960-1970. 7-10 flood events occurred during the wet period of 1961-1964 with very wet autumn, while only 1-2 events during the dry period of 1965-1969. Average annual specific sediment yield was 1.29×104 t km-2 a-1 for the Yuntaishan Gully during the period of 1960-1970, which was slightly higher than 1.11 ×104 t km-2 a-1 for the Upper Yanhe River Basin above the Ganguyi Hydrological Station and slightly lower than 1.40 ×104 t km-2 a-1 for the nearby Zhifang Gully during the same period. Annual specific sediment yields for the Yuntaishan Gully were correlated to the wet season's rainfalls well.