美国和加拿大的非联邦自动气象站（网）

1 引言 80年代美国和加拿大的非联邦自动气象站(AWS)和自动气象站网的数量,出现了惊人的增加。加利福尼亚、明尼苏达、内布拉斯加、北卡罗来纳和俄亥俄等州,都是70年代末80年代初首先建立非联邦AWS网的州。到1983年底,科罗拉多、佛罗里达、爱达荷、路易斯安娜、新墨西哥、纽约、     

由 CDSN 记录计算出的谱震级和地震辐射能

用10个数字化台的宽频带数字记录,计算了1986至1989年间发生在欧亚地震带上的18次 Ms6地震的谱震级和地震辐射能.10个数字化台中有9个属于中国数字化地震台网(CDSN),1个属于德国格拉芬堡台阵.计算得到的不同周期的谱震级,有的稳定性较好,有的稳定性较差.最大谱震级 mf和地震辐射能 E 稳定性较好,各台之间差异很小.特别是对于震中距较大,射线主要通过下地幔的台站,稳定性更好.而拐角周期的稳定性一般较差.辐射能与矩震级的关系满足lgE=1.5Mw+C,C 为常数.最大谱震级 mf=Mw+0.1,与理论预测值一致.      

Monitoring the sea change: preliminary assessment of the conservation value of nearshore reefs, and existing impacts, in a high-growth, coastal region of subtropical eastern Australia

In northern NSW, Australia, coastal populations are forecast to increase dramatically over the next 25 years (the "sea change"). However, management of the effects of development on marine communities is hampered by the lack of data on key habitats. Consequently, we developed a protocol to assess the biodiversity and current human impacts on nearshore reefs, habitats that will be readily affected by coastal development. We assessed four reefs adjacent to each of three population centres targeting fish, mollusc and sessile benthic communities, and debris loads. Community structure was highly variable over all spatial scales indicating that reefs should not be considered equivalent within the planning framework. While, debris loads were relatively low on most reefs, those with highest conservation value also had the highest debris loads suggesting potential conflict between human use and long-term sustainability of reefal communities. Without intervention, this situation will be exacerbated in the future.     

Comparison of approaches for predicting solute transport: sandbox experiments

The main purpose of this paper was to compare three approaches for predicting solute transport. The approaches include: (1) an effective parameter/macrodispersion approach (Gelhar and Axness 1983); (2) a heterogeneous approach using ordinary kriging based on core samples; and (3) a heterogeneous approach based on hydraulic tomography. We conducted our comparison in a heterogeneous sandbox aquifer. The aquifer was first characterized by taking 48 core samples to obtain local-scale hydraulic conductivity (K). The spatial statistics of these K values were then used to calculate the effective parameters. These K values and their statistics were also used for kriging to obtain a heterogeneous K field. In parallel, we performed a hydraulic tomography survey using hydraulic tests conducted in a dipole fashion with the drawdown data analyzed using the sequential successive linear estimator code (Yeh and Liu 2000) to obtain a K distribution (or K tomogram). The effective parameters and the heterogeneous K fields from kriging and hydraulic tomography were used in forward simulations of a dipole conservative tracer test. The simulated and observed breakthrough curves and their temporal moments were compared. Results show an improvement in predictions of drawdown behavior and tracer transport when the K tomogram from hydraulic tomography was used. This suggests that the high-resolution prediction of solute transport is possible without collecting a large number of small-scale samples to estimate flow and transport properties that are costly to obtain at the field scale.     

Topographic monitoring of a middle estuary mudflat, Humber estuary, UK--anthropogenic impacts and natural variation

Annual topographic surveys were carried out at the Saltend mudflat (Humber estuary, UK) between 1998 and 2006. These surveys formed part of an ongoing monitoring programme to examine the potential effects on the mudflat topography of the construction and operation of a waste water treatment works (WwTW) development by Yorkshire Water. Of particular concern was the potential disruption to the sedimentological regime within the special protection area (SPA) and candidate special area of conservation (cSAC) which could affect the invertebrate communities and ornithological functioning of the site. In addition to the development of the WwTW located to the extreme north-west of the site, a port extension removing 10ha of the Saltend intertidal mudflat (outside the SPA but immediately south east of the WwTW) also occurred between 1999 and 2006. Minimal change was noted across the site following the construction and operation of the WwTW between 1998 and 2000. However, the construction of the bund in closer proximity to the SPA and cSAC masked any potential impact the WwTW could have had across the site after 2000. Profiles and contour mapping indicate that significant mudflat accretion occurred in the immediate area of the bund, with a general increase recorded across the western section of the site since 2000. In contrast the alternations to channel planform and subsequent rapid accretion of the mudflat to the east of the jetty, being a significant distance from the developments, are attributed to natural cyclical changes.     

Field study of hydrogeologic characterization methods in a heterogeneous aquifer

Hydraulic conductivity (K) and specific storage (S(s)) are required parameters when designing transient groundwater flow models. The purpose of this study was to evaluate the ability of commonly used hydrogeologic characterization approaches to accurately delineate the distribution of hydraulic properties in a highly heterogeneous glaciofluvial deposit. The metric used to compare the various approaches was the prediction of drawdown responses from three separate pumping tests. The study was conducted at a field site, where a 15 m × 15 m area was instrumented with four 18-m deep Continuous Multichannel Tubing (CMT) wells. Each CMT well contained seven 17 cm × 1.9 cm monitoring ports equally spaced every 2 m down each CMT system. An 18-m deep pumping well with eight separate 1-m long screens spaced every 2 m was also placed in the center of the square pattern. In each of these boreholes, cores were collected and characterized using the Unified Soil Classification System, grain size analysis, and permeameter tests. To date, 471 K estimates have been obtained through permeameter analyses and 270 K estimates from empirical relationships. Geostatistical analysis of the small-scale K data yielded strongly heterogeneous K fields in three-dimensions. Additional K estimates were obtained through slug tests in 28 ports of the four CMT wells. Several pumping tests were conducted using the multiscreen and CMT wells to obtain larger scale estimates of both K and S(s). The various K and S(s) estimates were then quantitatively evaluated by simulating transient drawdown data from three pumping tests using a 3D forward numerical model constructed using HydroGeoSphere (Therrien et al. 2005). Results showed that, while drawdown predictions generally improved as more complexity was introduced into the model, the ability to make accurate drawdown predictions at all CMT ports was inconsistent.     

峰值速度和加速度对环境剪应力的依赖性

从导出的地震定标律和地震破裂过程的断裂力学模式出发,得到了震源平均位移、速度和加速度谱的表达式,进而又推导出震源的峰值位移d_m,速度v_m和加速度a_m的表达式:d_m=k_dM_0~2/~3τ_0~(2/3),v=k_vM_0~(1/3)τ_0~(4/3),a_m=k_aτ_0~2式中M_0是地震矩,τ_0是环境剪应力值,k_d,k_v,k_a为适当的常数.我们选用了66个地震的观测资料,这些地震的矩震级范围包括了从1级左右的极微震,3-5级的小震,直到6-7级的大震;地震矩从10~9-10~(20)Nm,跨越了10个数量级,并用这些地震检验了上述公式. 令所有地震的平均应力为5MPa,定出常数k_d,k_v,k_a,进而由速度和加速度观测资料求得66个地震的环境剪应力τ_0值,这些数值相当稳定.多数极微震的τ_0值在2-4MPa之间;小震的τ_0值多数在4-8MPa左右;大震的τ_0值为10MPa左右。τ_0值对震源深度和断层类型有明显的依赖性.一般深度很浅的小震和极微震,τ_0值很低;正断层地震的τ_0值相对较低;逆断层地震的τ_0值较高;走滑断层地震的τ_0值则居中.     

一种类似大洋中脊的斜长岩的成因

块状斜长岩成因模是同它在中-晚元古代非造山形成的横贯大陆带环境分不开的。然而,对产生富铝斜长石过饱和基性母液体的机理,仍难以理解,但它又是产生块状斜长岩的一个关键问题。通常斜长岩-苏长岩-橄长岩组合,反映了地幔同位素特征,并常与壳内花岗岩伴生。该特征与早期岩石圈扩张情况下,地幔和地壳内大量绝热熔融作用(Emslie,1980)相适应。岩浆的多期侵入、混合和系统的补充也很明显(Berg,1980),而且可以进一步表现元古代斜长岩-苏长岩-橄长岩系统的特征。它们与现代洋中脊的这类岩石相似(O′Hara和Mathews,1981)。虽然,没有人解释斜长岩的岩石性质和规模,但是,洋中脊玄武岩中斜