Crustal Structure of the Southern Korean Peninsula from Seismic Waves Generated by Large Explosions in 2002 and 2004

In order to investigate the velocity structure of the southern part of the Korean peninsula, seismic refraction profiles were obtained along a 294-km WNW-ESE line and a 335-km NNW-SSE line in 2002 and 2004, respectively. Seismic waves were generated by detonating 500–1000 kg explosives in drill holes at depths of 80–150 m. The seismic signals were recorded by portable seismometers at nominal intervals of 1.5–1.7 km. Separate velocity tomograms were derived from first arrival times using a series expansion method of travel-time inversion. The raypaths indicate several mid-crust interfaces including those at approximate depths of 2–3, 15–17, and 22 km. The Moho discontinuity with refraction velocity of 7.8 to 8.4 km/s has a maximum depth of 37–39 km under the southern central portion of the peninsula. The Moho becomes shallower as the Yellow Sea and the East Sea are approached on the west and east coasts of the peninsula, respectively. The depth of the 7.6 km/s velocity contour varies from 29.4 km to 36.5 km. The discrepancy in depth between the seismological Moho and the interpreted critically refracting interface may result from the presence of a gradual transition between the crust and mantle. The velocity tomograms show particular crustal structures including (1) the existence of an over 70-km wide low-velocity zone centered at 6–7 km depth under the Okchon fold belt and Ryeongnam massif, (2) existence of high-velocity materials under the Gyeongsang basin, and (3) the downward extension of the Yeongdong fault to depths greater than 10 km.     

由多震相走时和波形作三维地震成像

本项成果包括：提出天然地震走时反演层析成像技术,采用下列方法使得处理结果得以改善：１）利用３２个地震,４０４条射线的Ｐｇ,Ｓｇ,Ｐｍ,Ｓｍ,Ｐｎ,Ｓｎ等震相增加约束条件：２）用已有精度较高的人工地震测深化结果作速度约束;３）用波形反演来修改模型,把波源,介质吸收,散射等物理特征集中反映在记录中,把诸多物理量开发出来互为约束,以修改后的模型再作反演,使解的稳定性大大提高;４）采用最优化过程,选择遗传     

Relationship between value of open space and distance from housing locations within a community

This research uses a sequence of hedonic spatial regressions for a metropolitan housing market in the Southeastern United States to explore a new procedure that establishes the relationship between the value attributable to open space and distance from housing locations (a “distance-decay function”) within a given community. A distance-decay function allows identification of the range of distance over which open space affects housing values and the estimation of a proxy for the value added to nearby houses resulting from hypothetical open space preservation. Ex post analyses of the open-space regression coefficients suggest marginal implicit price functions for three types of open space that decay as open space area increases with respect to house location. After controlling for other factors in the spatial hedonic model, simple distance-decay functional relationships were established between the implicit prices of developed open space, forest-land open space, and agriculture-wetland open space and the buffer radius of the open-space areas surrounding a given housing location. The proposed method may be useful for identifying the range over which preferences for different types of open space are exhibited.     

Vision 2020: Towards an environmentally sound and sustainable development of freshwater resources in Malaysia

Malaysia has a climate of high humidity, high temperature and abundant rainfall. Rivers supply about 97% of the country's total water needs while ground water accounts for the rest. About 40% of the treated water is lost through man-caused leakages. With a population of 18.3 million people, the total annual domestic, industrial and irrigation water demand is about 11.6 x 106 MI. This figure is projected to rise to 15.2 x 106 MI by year 2000. At present, the total daily water demand is about 4,979 MI and the production capacity is 6,513 MI. Water use and misuse now strain the nation's fragile aquatic environment and natural ecosystems. Current water resource management priorities include water quality improvement, river rehabilitation to restore over-channalized or polluted rivers and development of the inland fisheries potential especially in large man-made reservoirs. A River Basin Information System has been developed to provide integrated information on catchment characteristics, landuse, population and socio-economic profile, river flow, pollution sources, water quality classification, and aquatic biota. Vision 2020 challenges call for a long-term perspective in inland water resource management. Critical post-audits of largescale development and strategic research aimed at alternative and interacting patterns of landwater use are urgently needed.     

一个重力仪零点校正的方法

引言一切重力儀的零點都不斷地發生或多或少的變化。為消除這種變化所引起的錯誤,在重力探勘中,大多用反覆测定的方法;但在整理測定的結果時,通常所用的方法,大多只有當零點變化和時間成正比時,才比較確定。若零點的變化不和時     

波谱分析仪

在地球物理學中,我們常常遇到這樣的問題:如何從在一定的觀測時間內所觀测得到的數據中,找出在所觀測的對象中潛伏着的週期性。众所周知,我們可以利用諧波分析及自相關方法（autocorrelation method）的數字計算以達到這個目的。但是,這樣做是頗為繁冗的。這里我們將要介紹一種波譜分析儀,用電子學     

Application of a second-order paraxial boundary condition to problems of dynamics of circular foundations on a porous layered half-space

A half-space finite element and a consistent transmitting boundary in a cylindrical coordinate system are developed for analysis of rigid circular (or cylindrical) foundations in a water-saturated porous layered half-space. By means of second-order paraxial approximations of the exact dynamic stiffness for a half-space in plane-strain and antiplane-shear conditions, the corresponding approximation for general three-dimensional wave motion in a Cartesian coordinate system is obtained and transformed in terms of cylindrical coordinates. Using the paraxial approximations, the half-space finite element and consistent transmitting boundary are formulated in a cylindrical coordinate system. The development is verified by comparison of dynamic compliances of rigid circular foundations with available published results. Examination of the advantage of the paraxial condition vis-á-vis the fixed condition shows that the former achieves substantial gain in computational effort. The developed half-space finite element and transmitting boundary can be employed for accurate and effective analysis of foundation dynamics and soil–structure interaction in a porous layered half-space.     

Hazard area and recurrence rate time series for determining the probability of volcanic disruption of the proposed high-level radioactive waste repository at Yucca Mountain, Nevada, USA

The post-12-Ma volcanism at Yucca Mountain (YM), Nevada, a potential site for an underground geologic repository of high-level radioactive waste in the USA, is assumed to follow a Poisson process and is characterized by a sequence of empirical recurrence rate time series. The last ten time series are used as a prediction set to check the predictive ability of the candidate model produced by a training sample using autoregressive integrated moving average modeling techniques. The model is used to forecast future recurrence rates that, in turn, are used to develop a continuous mean function of the volcanic process, which is not only required to evaluate the probability of site disruption by volcanic activity but accommodates a long period of compliance. At the model validation stage, our candidate model forecasts a mean number of 6.196 eruptions for the prediction set which accounts for seven volcanic events of the 33 post-12-Ma eruptions at the YM site. For a full-scaled forecasting, our fitted model predicts a waning volcanism producing only 3.296 new eruptions in the next million years. We then present the site disruption probability as the chance that a new eruption will occur in the “hazard area” based on a model developed for licensing commercial space launch and reentry operations in the space transportation industry. The results of the site disruption probability and sensitivity analysis are summarized with a numerical table generated from a simple equation sufficient for practical use. We also produce three-dimensional plots to visualize the nonlinearity of the intensity function associated with the underlying model of a nonhomogeneous Poisson process and emphasize that the interpretation of site disruption probability should always be accompanied by a compliance period.     

Simulation of the 1953 storm surge in the North Sea

The 1953 North Sea floods, the Big Flood, was one of the worst natural disasters in Europe in modern times and is probably one of the most studied severe coastal floods. Several factors led to the devastating storm surge along the southern North Sea coast in combination of strong and sustained northerly winds, invert barometric effect, high spring tide, and an accumulation of the large surge in the Strait of Dover. However, the storm waves and their roles during the 1953 North Sea storm surge are not well investigated. Therefore, the effect of wave setup due to breaking waves in the storm surge processes is investigated through numerical experiments. A coupled process-based tide-wave-surge model was used to investigate and simulate the storm surge in the North Sea during January 31–February 1, 1953 and validated by comparing with historical water level records at tide gauges and wave observations at light vessels in the North Sea. Meteorological forcing inputs for the period, January 27–February 3, 1953 are reproduced from ERA-20C reanalysis data with a constant correction factor for winds. From the simulation results, it is found that, in addition to the high water due to wind setup, wave setup due to breaking waves nearshore play a role of approximately 10% of the storm surge peaks with approximately 0.2 m. The resulting modeling system can be used extensively for the preparedness of the storm surge and wave of extreme condition, and usual barotropic forecast.