In the southern Sichuan Basin, China, the recent increase in the seismic activity has been suspected to be related to hydraulic fracturing stimulation for producing the shale gas. In this study, we used the monitoring data from a local seismic network within the shale gas blocks to study the earthquakes near the shale gas production wells that have detailed injection data. Comparison of the timing of earthquakes and stimulation schedule of the studied well pads indicates an apparent correlation between the seismic activity and hydraulic fracturing. The results of seismic velocity tomography reveal that the reactivation of preexisting faults due to fluid diffusion is the primary cause of the observed earthquakes. Focal mechanism analysis combined with geomechanical modeling indicates that the increased pore pressures resulted from hydraulic fracturing are sufficient to trigger seismic slip on the faults.

We report on the synthesis of the Si∕ZnS and Si∕ZnSe core/shell nanocrystal structures produced via a two-stage thermal evaporation of SiO and ZnS or SiO and ZnSe powder mixtures. These core/shell structures display spherical and elliptical polycrystalline particles. Most of the Si∕ZnS core/shell nanocrystal structures have diameters of ∼90–160nm; the diameters of the cores and the thicknesses of the shells vary in a range of ∼50–100nm. The diameters of the Si∕ZnSe core/shell nanocrystal structures range from ∼150 to ∼200nm; the thicknesses of the shells are rather uniform, ∼30nm, and the diameters of the cores are thus in the range of ∼120–170nm. Room-temperature photoluminescence was also investigated from as-synthesized Si/ZnS and Si/ZnSe core/shell nanocrystal structures, respectively.

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The interconnection of 1-D unsaturated cuprous coordination polymers [Cu2(μ4-L)]n and 1-D [(I−)·2I2·(I3)−]n polyiodide ribbons gives an unprecedented 3-D cuprous polyiodide network.