Coseismic displacement estimate of the 2013 <Emphasis Type="Italic">M</Emphasis><Subscript>S</Subscript>7.0 Lushan,China earthquake based on the simulation of near-fault displacement field

Usually, GPS observation provides direct evidence to estimate coseismic displacement. However, GPS stations are scattered, sparse and cannot provide a detailed distribution of coseismic displacement. Strong ground motion records share the same disadvantages as GPS in estimating coseismic displacement. Estimations from InSAR data can provide displacement distributions; however, the resolution of such methods is limited by the analysis techniques. The paper focuses on estimating the coseismic displacement of the M _S7.0 Lushan earthquake on April 20, 2013 using a simulation of the wave field based on the elastic wave equation instead of a quasi-static equation. First, the media and source models were constructed by comparing the simulated velocity and the record velocity of the ground motion. Then simulated static displacements were compared with GPS records. Their agreement validates our results. Careful analysis of the distribution of simulated coseismic displacements near the fault reveals more details of the ground motion. For example, an uplift appears on the hanging wall of the fault, rotation is associated with the horizontal displacement, the fault strike and earthquake epicenter provide the main control on motion near the faults, and the motion on the hanging wall is stronger than that on the footwall. These results reveal additional characteristics of the ground motion of the Lushan earthquake.     

Colloidal Stability and Toxicity of Gold Nanoparticles and Gold Chloride on <Emphasis Type="Italic">Chlamydomonas reinhardtii</Emphasis>

Here we have examined interactions of gold nanoparticles differing in primary particle size and coating with the green algae Chlamydomonas reinhardtii as function of the colloidal stability of the particles in the experimental media used for toxicity studies. Interactions of dissolved Au³⁺ ions with algae were also examined. Included endpoints were photosynthetic yield and algal growth. Morphological and structural effects were examined microscopically and by flow cytometry. The results indicate no significant toxicity of gold nanoparticles to C. reinhardtii. Analysis of published data suggests toxicity of gold nanoparticles on algal growth to relate rather to particular coatings than to the gold core.     

Is tidal forcing critical to trigger large Sumatra earthquakes?

Complexity in the earthquake mechanism is manifested in different forms such as fractal distribution, clustering of seismicity, etc., and characterized as critical phenomenon. Occurrences of earthquakes generally represent the state of metastable equilibrium. The Andaman–Sumatra subduction zone is one of the most seismically active corridors (possibly in metastable state) in the world. Recently, the region faced three major earthquakes of magnitude more than 8.5 (M ~ 9.1 on December 26, 2004; M ~ 8.6 on March 28, 2005; M ~ 8.6 on April 11, 2012). Researchers have suggested multiple causes of earthquake generation in this region including the one with possible correlation of tidal stresses with earthquake occurrences. The latter issue, however, has been hotly debated in view of the fact that a small stress generated due to tidal forcing cannot cause such a bigger magnitude earthquake. We study here the impact of tidal forcing on critically generated earthquake phenomena. We examined the statistical behavior of recurrence time interval of earthquakes using the available data for period of about 40 years from 1973 to 2013. We constrain the simple empirical toy model using the concept of catastrophe theory to evaluate the impact of small tidal forcing on the critical state of earthquakes occurrences. In addition to the major role of Helmholtz free energy during the plate motion, our analysis suggests that the stability and critical behavior of the earthquake in Sumatra region could be associated with tidal forcing, however, only for triggering of some of the “Catastrophic–Chaotic” earthquake phenomenon.     

Spatiotemporal variation of meteorological droughts based on the daily comprehensive drought index in the Haihe River basin,China

Meteorological droughts can affect large areas and may have serious environmental, social and economic impacts. These impacts depend on the severity, duration, and spatial extent of the precipitation deficit and the socioeconomic vulnerability of the affected regions. This paper examines the spatiotemporal variation of meteorological droughts in the Haihe River basin. Meteorological droughts events were diagnosed using daily meteorological data from 44 stations by calculating a comprehensive drought index (CI) for the period 1961–2011. Based on the daily CI values of each station over the past 50 years, the drought processes at each station were confirmed, and the severity, duration and frequency of each meteorological drought event were computed and analyzed. The results suggest the following conclusions: (1) the use of the CI index can effectively trace the development of drought and can also identify the duration and severity of each drought event; (2) the average drought duration was 57–85 days in each region of the Haihe River basin, and the region with the highest average values of drought duration and drought severity was Bohai Bay; (3) drought occurred more than 48 times over the study period, which is more than 0.95 times per year over the 50 years studied. The average frequencies of non-drought days, severe drought days and extreme drought days over the study period were 51.2, 3.2 and 0.4 %, respectively. Severe drought events mainly occurred in the south branch of the Hai River, and extreme drought events mainly occurred in the Shandong Peninsula and Bohai Bay; (4) the annual precipitation and potential evapotranspiration of the Haihe River basin show decreasing trends over the past 50 years. The frequency of severe drought and extreme drought events has increased in the past 20 years than during the period 1961–1990. The results of this study may serve as a reference point for decision regarding basin water resources management, ecological recovery and drought hazard vulnerability analysis.     

Fish Interactions with a Commercial-Scale Tidal Energy Device in the Natural Environment

Fish are a key part of the marine ecosystem likely to be affected by hydrokinetic tidal turbines, but little is known about their behavior around such obstacles in the natural environment. In September 2010, two DIDSON acoustic cameras were used to observe fish interactions with a commercial-scale turbine in Cobscook Bay, Maine. Twenty-two hours (nearly two tidal cycles) of footage were collected. Behaviors of individual fish and schools were classified (e.g., entering, avoiding, passing, or remaining in the wake of the turbine). We analyzed the effects of turbine motion (rotating or not rotating), diel condition (day or night), and fish size (small, ≤10 cm; large, >10 cm) on individual fish behaviors, and compared behaviors of individual fish to schools of fish. When the turbine was rotating, the probability of fish entering the turbine decreased by over 35 % from when it was not. The probability that fish would enter the turbine was higher at night than during the day, and this difference was greater for small fish than for large fish (probability of small fish entering?=?0.147 day, 0.513 night; large fish?=?0.043 day, 0.333 night). Fish were almost always present in the wake of the turbine. Schools of fish had a 56 % lower probability of entering the turbine than individual fish, and reacted at greater distances from the turbine (median distance of 2.5 m for schools, 1.7 m for individuals). This study indicates that fish behavior in response to tidal turbines appears to be similar to responses to obstacles such as trawls, and highlights the importance of environmental context in determining the effects of a tidal turbine on fish.     

Geochemical characteristics of island-arc volcanic rocks in the Nan-Nam Pat-Phetchabun zone,northern Thailand

Late Permian-Early Triassic (P₂-T₁) volcanic rocks distributed on the eastern side of ocean-ridge and oceanic-island basalts in the Nan-Uttaradit zone were analyzed from aspects of petrographic characteristics, rock assemblage, REE, trace elements, geotectonic setting, etc., indicating that those volcanic rocks possess the characteristic features of island-arc volcanic rocks. The volcanic rock assemblage is basalt-basaltic andesite-andesite. The volcanic rocks are sub-alkaline, dominated by calc-alkaline series, with tholeiite series coming next. The chemical composition of the volcanic rocks is characterized by low TiO₂ and K₂O and high Al₂O₃ and Na₂O. Their REE patterns are of the flat, weak LREE-enrichment right-inclined type. The trace elements are characterized by the enrichment of large cation elements such as K, Rb and Ba, common enrichment of U and Th, and depletion of Nb, Ta, Zr and Hf. The petrochemical plot falls within the field of volcanic rocks, in consistency with the plot of island-arc volcanic rocks in the Jinsha River zone of China. This island-arc volcanic zone, together with the ocean-ridge/oceanic island type volcanic rocks in the Nan-Uttaradit zone, constitutes the ocean-ridge volcanic rock-island-arc magmatic rock zones which are distributed in pairs, indicating that the oceanic crust of the Nan-Uttaradit zone once was of eastward subduction. This work is of great significance in exploring the evolution of paleo-Tethys in the Nan-Uttaradit zone.     

Physical and chemical changes of water in the deep interior of the Earth—Decrepitation-style mud-volcano-earthquake—A bright lamp to shed light on the mysteries of the deep interior of the Earth

The 2008-05-12 Wenchuan mud-volcano-earthquake was accompanied with eruption of a huge volume of gas and stone, revealing that earthquakes generally result from instant reverse phase explosion of supercritical water (SCW) at the supercritical point. In the deep parts of the crust and mantle there still exists a large amount of supercritical water equivalent in order of magnitude to that of the Earth’s hydrosphere. Soft fluids which exist in the MOHO at the top of the upper mantle are the so-called deep supercritical fluids (SCWD). Supercritical water (SCW) has n×10³ times strong capability to dissolve gas. Its viscosity is extremely low and its diffusivity is extremely strong. Therefore, it can naturally migrate toward a region with relatively negative pressure. In the steep break zone of the MOHO at the 57–65 km depth beneath the earthquake belt, due to mutation of overburden pressure, SCWD can automatically separate out CaSiO₃ and other inorganic salts, evolving into the SCW (H₂O-CO₂-CH₄O system. In going upwards to the 10–20-km depth of the crust SCW will be accumulated as an earthquake-pregnant reservoir in the broken terrain. The phase-transition heat of SCW is estimated at 606.62 kJ/kg and the reverse phasing kinetic energy is 2350.8 kJ/kg. When automatic exhaust at the time of decompression reaches the critical pressure (Pc), the instant explosion reverse phase will be normal-state air water. It will release a huge volume of energy and high-kinetic-energy gas which has been expanded by a factor of 1000, leading to the breaking of the country rocks overlying the earthquake-pregnant reservoir, thus giving rise to a Ms 8.0 earthquake. As a result, there were formed eruptive and air-driven (pneumatic) debris flows whose volumatric flow rate reaches n×10¹⁴ m³/s, and their force greatly exceeds the power of INT explosive of the same equivalent value.     

Evolution of isotopic compositions in groundwater of the area between the Gulf of Oman and the Arabian Gulf

The stable isotopes of oxygen and hydrogen have been implemented to assess the recharge mechanisms in an area in the UAE bounded to the northwestern part of the Gulf of Oman and the southeastern part of the Arabian Gulf. The conversion of stable isotopes to deuterium excess was utilized as a supportive tool to understand the process of groundwater recharge. The concluding results of this study showed that the origin of moisture is the Mediterranean Sea. The precipitation is the main source of recharge, in which the precipitation having undergone evaporation before recharge occurs. The comparison between regression line for data collected in 1996 and regression line for samples collected in 2006 suggests that the precipitation water which recharged the groundwater, was diluted with groundwater and this dilution is observed from decreasing of the deuterium excess of collected groundwater samples with increasing isotopes of oxygen. The dilution of groundwater with the recharge water suggests modern-day recharge as it is seen from high deuterium excess that exceeded the deuterium excess of LMWL and was close to MMWL.     

Source apportionment and distribution of atmospheric mercury in urban Beijing,China

The concentration of gaseous elemental mercury (GEM) in the atmosphere of urban Beijing was measured from October 2003 to September 2004 to investigate the origins and spatial-temporal variations of atmospheric Hg. The mean value of Hg concentration is 17.1 ng·m-3 (n=653). The atmospheric Hg data showed spatial-temporal variations throughout the duration of our observation. The maximum GEM concentration (53.7 ng·m-3) was observed at Gucheng in the western area of urban Beijing. The GEM concentrations increased from the north to the south of the studied area, and were higher in winter than in summer. The highest and lowest monthly averages of GEM concentrations were measured to be 23.3 and 4.1 ng·m-3 in January and July, respectively. In addition, GEM concentrations are higher in the daytime than at night in Autumn and from 14 March to 15 April, but daily GEM variation showed an inverse pattern from 22 April to 22 May. In winter, two peak values of GEM concentrations occurred at 13:30 and 21:30. Daily variation of GEM concentrations in summer was the lowest in the four seasons. Mercury from coal combustion was estimated to be the main source of anthropogenic emissions in Beijing from October 2003 to September 2004. Additionally, Hg emission from natural gas burning was estimated to be another dominant source of atmospheric Hg in Beijing.     

Active spreading and hydrothermalism in North Fiji Basin (SW Pacific). Results of Japanese French Cruise Kaiyo 87

The aim of the Japanese-French Kaiyo 87 cruise was the study of the spreading axis in the North Fiji Basin (SW Pacific). A Seabeam and geophysical survey allowed us to define the detailed structure of the active NS spreading axis between 16° and 22° S and its relationships with the left lateral motion of the North Fiji Fracture Zone. Between 21° S and 18°10′ S, the spreading axis trends NS. From 18°10 S to 16°40 S the orientation of the spreading axis changes from NS to 015°. North of 16°40′ S the spreading axis trends 160°. These two 015° and 160° branches converge with the left lateral North Fiji fracture zone around 16°40′ S to define an RRFZ triple junction. Water sampling, dredging and photo TV deep towing give new information concerning the hydrothermal activity along the spreading axis. The discovery of hydrothermal deposits associated with living communities confirms this activity.