Relationship between the seismicity and geologic structure of the Blanco Transform Fault Zone

Morphologic studies of an oceanic transform, the Blanco Transform Fault Zone (BTFZ), have shown it to consist of a series of extensional basins that offset the major strike-slip faults. The largest of the extensional basins, the Cascadia Depression, effectively divides the transform into a northwest segment, composed of several relatively short strike-slip faults, and a southeast segment dominated by fewer, longer faults. The regional seismicity distribution (m _b 4.0) and frequency-magnitude relationships (b-values) of the BTFZ show that the largest magnitude events are located on the southeast segment. Furthermore, estimates of the cumulative seismic moment release and seismic moment release rate along the southeast segment are significantly greater than that of the northwest segment. These observations suggest that slip along the southeast segment is accommodated by a greater number of large magnitude earthquakes. Comparison of the seismic moment rate, derived from empirical estimates, with the seismic moment rate determined from plate motion constraints suggests a difference in the seismic coupling strength between the segments. This difference in coupling may partially explain the disparity in earthquake size distribution. However, the results appear to confirm the relation between earthquake size and fault length, observed along continental strike-slip faults, for this oceanic transform.     

Thermohaline Anomalies in the Spring and Early Summer of 2000 in the Gulf of Trieste

Abstract. In the framework of the Interreg II Project (July 1998 - June 2001), hydro-logical, chemical and biological data were collected in the Gulf of Trieste.
During spring and summer 2000, some particular thermohaline anomalies were observed in the Gulf of Trieste. Especially in May and June the water body showed: a very strong thermohaline stratification, an increase of advective salt water coming from the south and the presence of sharp pycnoclines. In July the temperature was higher than usual in the whole water column. Moreover, in late May and in June, massive mucilaginous aggregates were observed along the water column and at the surface.
In order to highlight these particular thermohaline features the hydrological data of 16 stations were analysed (Fig. 1). Two stations, in particular, were considered: one offshore (St. AA1, average depth 20 m) and one close to the coast (St. C1, average depth 17 m). For these two stations a best-fit analysis, computed over 11 and 7 years, respectively, was performed on temperature, salinity and density excess data.
Moreover, the hydrological features were compared with the rainfall, air temperature, wind speed data (Istituto Sperimentale Talassografico di Trieste - ISTT) and the Isonzo River's flow rate (Direzione Regionale dell'Ambiente - Regione F. V. G.) collected from January 1998 to December 2000.     

Optical properties of low molecular weight and colloidal organic matter: Application of the ultrafiltration permeation model to DOM absorption and fluorescence

Cross-flow ultrafiltration (CFF) is often used to obtain separation and concentration of colloids from bulk natural water samples. Application of the ultrafiltration permeation model allows the quantitative determination of the low molecular weight material (LMW, < 1 kDa) and colloids in bulk dissolved organic matter (DOM) from measurements of time series permeate samples obtained from CFF. Detailed analysis of a Yukon River water sample shows that DOM absorption coefficient and fluorescence follow the permeation model and that the complex spectral optical properties of LMW DOM can be reconstructed from CFF data. A combination of measured and modeled data indicates that the LMW contribution to bulk DOM optical properties obtained from CFF can be grossly underestimated by the use of a low concentration factor (CF, the ratio of initial sample volume to retentate volume). Even at a relatively high CF of 19, optical properties of LMW DOM calculated from measurements of the retentate or integrated permeate would underestimate true values by 5–36%. In the Yukon River sample, LMW dissolved organic carbon represented 26% of the bulk concentration, but only 3–14% of the colored DOM was in the LMW fraction while 31–33% of bulk DOM florescence was due to LMW DOM. The contrasting optical properties of LMW and colloidal DOM support the concept that analysis of bulk DOM absorption and fluorescence properties reveals information about DOM molecular weight.     

Tectonic Significance of the Taitung Canyon, Huatung Basin, East of Taiwan

Since the beginning of formation of Proto-Taiwan, the subducting Philippine (PH) Sea plate has moved continuously through time in the N307° direction with respect to Eurasia (EU), tearing the EU plate. The subducting EU plate includes a continental part in the north and an oceanic part in the south. The boundary B between these two domains corresponds to the eastern prolongation of the northeastern South China Sea ocean-continent transition zone. In the Huatung Basin (east of Taiwan), the Taitung Canyon is N065° oriented and is close and parallel to B. Seismic profiles show that the southern flank of the canyon corresponds to a fault with a normal component of a few tens of meters in the sediments and possible dextral shearing. Several crustal earthquakes of magnitude >%6 are located beneath the trend of the Taitung Canyon and focal mechanisms suggest that the motion is right-lateral. Thus, faulting within the sedimentary sequence beneath the Taitung Canyon is a consequence of underlying dextral strike-slip crustal motions. As the continental part of the EU slab located north of B has been recently detached, some subsequent dextral strike-slip motion might be expected within the EU slab, along the ocean-continent transition zone, which is a potential zone of weakness. We suggest that the dextral strike-slip motion along the ocean-continent boundary of the EU slab might trigger the observed dextral strike-slip motion within the overlying PH Sea crust and the associated faulting within the sediments of the Huatung Basin, beneath the Taitung Canyon. An erratum to this article is available at .     

九龙江流域水葫芦打捞去除水体营养盐模型研究

水葫芦被收获时,水体中的营养盐也将包含在植物组织中而被去除.本研究首先通过野外实验和参考国内外有关文献,建立了九龙江流域水葫芦生长数学模型和持续生产模型,确定了模型的各有关参数:水葫芦生长容量K值为25.6 kg/m2、最大生长速率rmax为0.12d-1;水体中氮和磷的半饱和系数hN和hP值分别为0.2和0.03;水葫芦最低生长温度(mθin)为7℃,最适水温(oθpt)为30℃,最高生长温度(θmax)为40℃.随后采用所建立的模型计算了研究区水葫芦打捞的营养盐去除效果,研究区面积6 000m2的水体实施水葫芦打捞策略后,1a所能收获的水葫芦最大产量为9.18×105kg,去除的TP为214.4kg,TN为966.6kg.     

Particulate and dissolved amino acids in the lower Mississippi and Pearl Rivers (USA)

In this study, we present seasonal changes (monthly samples from September 2001 to August 2003) in the abundance and composition of dissolved and particulate amino acids, at one station in the lower Mississippi and Pearl Rivers (LA, MS: USA). Spatial changes over a 4-day transmit from river km 390 to river mouth (Head of Passes, LA) in the Mississippi River, and a two-day downstream sampling from Jackson (MS) to Stennis Space Center (MS) were also determined. Temporal data in the lower Mississippi River showed significantly lower concentrations of dissolved combined amino acids (DCAA, 0.8 to 2.2 μM) and dissolved amino acids in high molecular weight fraction (HMW DAA, 0.2–0.4 μM) than in the Pearl River (DCAA, 1.4–4.3 μM; HMW DAA, 0.4–1.4 μM). Dissolved free amino acids (DFAA) were significantly lower than DCAA in both rivers, and displayed minimal seasonal variability. DCAA, HMW DAA, and particulate amino acids (PAA) were generally higher during high-flow periods, which may have suggested dominance in terrestrial sources. Carbon-normalized yield of PAA (%C-PAA) was generally higher during low-flow conditions and positively correlated with chlorophyll-a (chl-a), reflective of in situ sources. Downstream variability in the lower Mississippi River showed stable DCAA concentrations, a decline in PAA (from 1.06 to 0.43 μM), and a gradual increase in mole percent of non-protein amino acids (%NPAA). This likely reflected bacterial degradation of phytoplankton biomass during falling discharge. Nitrogen-normalized yield of PAA (%N-PAA) was inversely correlated with PAA (R = − 0.7, n = 48), indicative of short-term sedimentation and resuspension events. Conversely, downstream decreases in DCAA and middle-reach peaks of PAA and %N-PAA in the Pearl River, likely resulted from photochemical degradation of DOM as well as algal production during base-flow conditions. The comparisons in abundance and composition of DAA and PAA in these different river systems provides important information on in situ nitrogen and carbon cycling as related to riverine inputs of organic matter to coastal ocean.     

Shoreline variability via empirical orthogonal function analysis: Part I temporal and spatial characteristics

Empirical orthogonal functions (EOFs) or principal components were used to extract the significant modes of shoreline variability from several data sets collected at three very different locations. Although EOFs have proven to be a valuable tool in the analysis of nearshore data, most applications have focused on the ability of the technique to describe cross-shore or profile variability. Here however, EOFs were used to help identify the dominant modes of longshore shoreline variability at Duck, North Carolina, the Gold Coast, Australia, and at several locations within the Columbia River Littoral Cell in the U.S. Pacific Northwest. In part one of this analysis, characteristic patterns of shoreline variability identified by the EOF analysis are described in detail. At each site, the dominant modes consisting of the first four eigenfunctions were found to describe nearly 95% of the total shoreline variability. At both Duck and the Gold Coast, several interesting longshore periodic features suggestive of sand waves were identified, while boundary effects related to natural headlands and navigational structures/entrances dominated the Pacific Northwest data sets.     

等高线自动绘制中断层处理的新方法

提出了一种断层处理新方法——分块法与断层恢复法合成算法，这种方法兼有分块法与断层恢复法的优点同时又克服了其不足，较好地解决了含逆断层时煤层底板等高线自动绘制及任意边界的构网问题，使绘出的等值线图误差较小，更加符合实际。     

软土海岸地区测量控制点标志的设立

分析了软土、湿地、滩涂地区特殊地理环境对测量控制点的影响;主要探讨了此类地区控制点标志的设计、施工。借助于建筑桩基技术和道桥施工方法,首次成功实现了某三角洲湿地滩涂地区统一布网。几年来,结合滩涂湿地测量、海岸防护和滩涂开发工程对部分控制点进行了初步检测,给出了部分检测数据。应用和检测均表明:桩基标石可较好地解决软土、湿地、滩涂地区控制点布设难题,显著提高软土海岸地区测量控制点标志的稳固性,从而延长控制网的可使用期。     

黄河尾闾河道1996年改道的意义及黄河三角洲演化趋势

现代黄河三角洲由几个亚三角洲组成。 1 85 5 -1 93 4年 ,形成了以宁海为顶点的第一亚三角洲 ;1 93 4-1 996年 ,三角洲冲积扇顶点进一步下移 ,形成了以渔洼为顶点的第二亚三角洲。最近的一次改道是在 1 996年 6月 ,改道后的河流沿清水沟流路的清 8剖面附近东流入海。这次改道可能是第三亚三角洲形成的开始。以后数十年内的黄河尾闾摆动将在清 8剖面附近进行。虽然人类活动将对三角洲的发展演化产生越来越明显的影响 ,但这些亚三角洲的发育演化仍有明显的规律性