Air-sea exchange of mercury in Tokyo Bay

In Tokyo Bay the concentrations of dissolved gaseous mercury (DGM) in the surface seawater and total gaseous mercury (TGM) over the sea were measured during December 2003, October 2004 and January 2005. Based on these data, the evasional fluxes of mercury from the sea surface were estimated using a gas exchange model. In addition, an automatic wet and dry deposition sampler was used to measure the wet and dry depositional fluxes of mercury from December 2003 to November 2004 at three locations in and near Tokyo Bay. The results indicate that the average DGM and TGM levels of seven locations are 52 ± 26 ng m⁻³ and 1.9 ± 0.6 ng m⁻³, respectively, which shows that the surface seawater in Tokyo Bay is supersaturated with gaseous mercury, leading to an average mercury evasional flux of 140 ± 120 ng m⁻²d⁻¹. On the other hand, the annual average wet and dry depositional fluxes of mercury at three locations were 19 ± 3 μg m⁻²yr⁻¹ and 20 ± 9 μg m⁻²yr⁻¹, respectively. These depositional fluxes correspond to the daily average total depositional flux of 110 ± 20 ng m⁻²d⁻¹. Thus, it is suggested that in Tokyo Bay, the evasional fluxes of mercury are comparable to the depositional fluxes.     

Regional characteristics of stress field in the southern part of the north－south seismic belt in China and its relation with plate movement

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Concentration level of dissolved cadmium and its variation in surface seawater of Urasoko Bay,Ishigaki Island

From April 2005 to March 2006, the concentration of dissolved cadmium (Cd) was monitored in the surface seawater of Urasoko Bay, which is in a subtropical area of the North Pacific Ocean and is surrounded by a well-developed fringing reef. During this period, the observed salinity and Cd concentrations varied in a range of approximately 16–34.5 and 4.8–77.8 pM, respectively. The concentration range of Cd obtained in this study was considered to be too low to damage the coral species, and its variation throughout the year did not show any seasonality and was not connected with climate data. The Cd-salinity plot for all the data in the salinity range over 26 showed apparent non-conservative behavior, which suggests a possible irregular input of Cd from a solid phase through streams and groundwater, release from bottom sediments, and atmospheric deposition into the bay.     

Pi-SAR极化数据与K分布指数估算森林生物量与实验验证

用2002年和2003年日本Pi-SAR全极化数据,研究日本北海道苫小牧森林地区的森林生物量.雷达后向散射系数随森林生物量的增大而增大并迅速达到饱和,L波段雷达数据饱和点约为40t/hm2,X波段仅约为20t/hm2.在SAR数据统计分布中,K分布的指数参数在饱和点以上仍随生物量的增大而增大,并且HV极化方式时相关性最高.根据交叉极化数据K分布的指数参数与森林生物量的关系,本文估算了23个观测点的森林生物量,结果表明平均准确率为85%.因此该算法可以作为一种新的估算森林生物量的手段.     

Multi‐scale Decomposition of Co‐seismic Deformation from High Resolution DEMs: a Case Study of the 2004 Mid‐Niigata Earthquake

Decomposing co-seismic deformation is an immediate need for researchers who are interested in earthquake inversion analysis and geo-hazard mapping. However, conventional InSAR or digital elevation models (DEMs) imagery analyses only provide the displacement in the Line-of-Sight (LOS) direction or elevation changes. The 2004 Mid-Niigata earthquake in Japan provides lessons on how to decompose co-seismic deformation from two sets of DEMs. If three adjacent points undergo a rigid-body-translation movement, their co-seismic deformation can be decomposed by solving simultaneous equations. Although this method has been successfully used to discuss tectonic deformations, the algorithm needed improvement and a more rigorous algorithm, including a new definition of nominal plane, DEMs comparability improvement and matrix condition check is provided. Even with these procedures, the obtained decomposed displacement often showed remarkable scatter prompting the use of the moving average method, which was used to determine both tectonic and localized displacement characteristics. A cut-off window and a pair of band-pass windows were selected according to the regional geology and construction activities to ease the tectonic and localized displacement calculations, respectively. The displacement field of the tectonic scale shows two major clusters of large lateral components, and coincidently major visible landslides were found mostly within them. The localized displacement helps to reveal hidden landslides in the target area. As far as the Kizawa hamlet is concerned, the obtained vectors show down-slope movements, which are consistent with the observed traces of dislocations that were found in the Kizawa tunnel and irrigation wells. The method proposed has great potential to be applied to understanding post-earthquake rehabilitation in other areas.     

Assessment of the Stability of Rock Slopes by the Slope Stability Rating Classification System

Given the lack of suitable systems in the characterization of slope stability of heavily jointed rock masses, a new rock mass classification system called Slope Stability Rating (SSR) is proposed. In addition to the so-called modified Geological Strength Index, the proposed system considers five additional parameters whose relative effects on the stability of fractured rock slopes were precisely examined based on data retrieved from eight different rock slope sites in Iran. An overall rating for the rock mass is obtained from the summation of the individual ratings of each parameter. A number of design charts are provided as illustration. The new system was then validated based on 46 slope case histories from Iran and Australia. For this, by means of the design charts previously mentioned, a recommended stable angle for each slope was given and compared with the current slope conditions. As a result, SSR design charts for maximum excavation angle (FS = 1.0) and also for other more conservative excavation angles (FS = 1.2, 1.3, 1.5) were presented.     

Experimental frictional heating of coal gouge at seismic slip rates: Evidence for devolatilization and thermal pressurization of gouge fluids

High velocity (1 m/s) friction experiments on bituminous coal gouge display several earthquake-related phenomena, including devolatilization by frictional heating, gas pressurization, and slip weakening. Stage I is characterized by sample shortening and reduction in the coefficient of friction (μ) from  1 to 0.6. Stage II is characterized by high frequency ( 5 Hz) oscillations in stress and strain records and by gas emissions. Stage III is marked by rapid weakening (μ  0.1 to 0.35) and sample shortening, together with continued gas emissions. Stage IV produces stable stress records and continued weakness (μ  0.2), but without gas emission. Stage I shortening is due to compaction of the gouge and the weakening is attributed to mechanical or thermal effects. Stage II behavior is interpreted as due to coal gasification and fluctuations in fluid pressure, resulting in high frequency stick-slip type behavior. Dramatic reduction in shear stress in stage III is attributed to gas pressurization by pore collapse and corresponds to a frictional instability, analogous to nucleation of an earthquake. Microstructural observations indicate the deformation was brittle during stages I and II but ductile during stages III and IV. Time dependent finite element frictional heat models indicate the center of the samples became hot ( 900 °C) during stage II, whereas the edge of samples remained relatively cold (< 300 °C). Vitrinite reflectance of coal samples shows an increase in reflectance from  0.5 to  0.8% over the displacement interval 20–40 m (20–40 s), indicating that the reflectance responds to frictional heating on a short time scale. The energy expended per unit area in these low stress, large displacement experiments is similar to that of higher stress ( 50 MPa), short displacement ( 1 m) earthquakes ( 10⁷ J/m²).     

Measurement of debris mass changes and assessment of the dam-break flood potential of earthquake-triggered Hattian landslide dam

The Hattian landslide, which was triggered by the 2005 Kashmir earthquake, formed one of largest landslide dams in the world and it has posed a serious threat of flooding to people living in the lower reach of the Jhelum River. In order to understand deformation occurring in the body of the dam, physical measurements using a Differential Global Positioning System (DGPS) were conducted. Gradual deformation and slowly developing backward erosion initially were observed, leading eventually to a sudden creation of a deep hollow on the downstream slope of the landslide dam. The dimensions of this eroded gully were determined by laser scanning, and the results showed a significant loss of soil volume and a large change in the body of the dam. A breach formation model was used to predict the outflow hydrograph generated by constant downcutting of dam during a breaching event. A run-off analysis of the outflow hydrograph was conducted to evaluate inundation levels of flood waves in case the dam is breached. Hazardous downstream locations were identified near the junction of the Karli and Jhelum Rivers, suggesting a need for early warning system in order to avoid loss of lives.