南极洲普里兹湾岩石圈各向异性:海底地震仪观测

为了研究南极普里兹湾岩石圈深部应力场及其动力学,采用S波分裂旋转相关法,对中国第31次南极科学考察成功回收的3个站位海底地震仪数据(5个远震记录)进行了反演,获得了普里兹湾洋陆过渡带岩石圈各向异性特征.结果表明,台站所在区域各向异性显著,在较小的范围内存在明显的空间差异,快S波偏振方向变化范围是N40°E ~ N60°E,快慢波时间延迟变化范围为0.2~1.3 s.洋盆的各向异性主要取决于海底扩张地幔流作用,大陆及附近的各向异性主要受上地幔顶部残留构造的影响,而中间过渡带各向异性层厚度较小集中在地壳内,它可能受海底扩张地幔流和残留构造共同作用.      

南海海底地震仪三维深地震探测的进展及挑战

获取深部速度结构是认识南海形成演化模式的基础.海底地震仪（OBS）二维与三维深地震探测技术是获取深部速度结构最成功的方法之一.OBS三维探测结果揭示:西南次海盆横跨残留扩张脊两侧洋壳不对称增生的速度结构特征;东部次海盆具有4种不同洋壳类型的速度结构;珍贝-黄岩海山链是在海盆停止扩张后6~10 Ma岩浆活动形成的;东沙隆起区显示了张裂期后的岩浆活动及其上涌通道;南海东北部马尼拉俯冲带前缘是受到张裂期后岩浆活动影响的减薄陆壳.IODP367-368钻探区实施的OBS三维探测将以建立南海洋陆转换带（COT）张裂-破裂机制模型为科学目标.OBS三维探测方法在南海各向异性、岩浆活动、形成演化等方面将继续发挥着不可替代的作用.      

渤海海底地震仪探测试验及初步成果

利用大容量气枪枪阵震源和海底地震仪在渤海首次开展人工地震深部地球物理探测试验。本次试验布设一条NWW-SEE向垂直构造走向的勘测线,共投放海底地震仪51台,回收成功50台。试验结果和数据分析表明,所使用的枪阵有足够的能量输出,海底地震仪记录震相丰富,可识别到Ps,Pg,PmP,Pn等多种震相。初至波层析成像结果表明,9 km以上地层速度结构存在明显的横向不均匀性,渤中地区新生代沉积基底埋深5～6 km,结晶基底埋深约9 km,郯庐断裂带内存在"U"型下凹的相对低速体并有向下切割的趋势。此次试验是我国在渤海深部探测中的成功示范,有效填补了渤海海域深地震测深数据的空白,为渤海深部地壳结构研究及含油气盆地形成演化研究提供了重要的基础资料。     

Accurate Ocean Bottom Seismometer Positioning Method Inspired by Multilateration Technique

The positioning of ocean bottom seismometers (OBS) is a key step in the processing flow of OBS data, especially in the case of self popup types of OBS instruments. The use of first arrivals from airgun shots, rather than relying on the acoustic transponders mounted in the OBS, is becoming a trend and generally leads to more accurate positioning due to the statistics from a large number of shots. In this paper, a linearization of the OBS positioning problem via the multilateration technique is discussed. The discussed linear solution solves jointly for the average water layer velocity and the OBS position using only shot locations and first arrival times as input data.     

海底地震仪(OBS)主动源转换横波的应用

横波（S波）为偏振波,具有不同于纵波（P波）的特性,对于地震探测具有特殊的意义.在被动源地震探测中已得到广泛的应用,如接收函数、S波分裂等.在主动源（气枪）海底地震（OBS）探测中,震源在水中,S波为地层转换波,其应用还不多.本文在介绍转换S波的产生、模式、处理和识别的基础上,以实例为切入点简述其具体应用.这些应用主要是基于1D/2D转换S波,用于揭示海底岩石类型、推断地壳性质、共轭陆缘问题、判定地幔蛇纹石化、估算天然气水合物的饱和度和预测流体等.目前在南海已获得了大量的2D和3D的OBS转换S波数据,可将转换S波的研究逐步从2D发展到3D研究,同时结合其他地球物理资料进行共同分析.利用转换S波的研究,有利于揭示南海扩张停止后形成的海山下不同地层的岩性和判定上地幔低速的性质等.      

New Data on Seismotectonics of the Laptev Sea from Observations by Ocean Bottom Seismographs

Doklady Earth Sciences - The results of new local seismic observations in the Laptev Sea obtained using ocean bottom seismographs were compared with actual data from global and regional earthquake...     

Gas-Geochemical Parameters of Bottom Sediments in the Northern Part of the East Siberian Sea and Podvodnikov Basin of the Arctic Ocean

Doklady Earth Sciences - New data on the gas and chemical composition of bottom sediments of the marginal-shelf part of the East Siberian Sea, continental slope, and Podvodnikov Basin of the Arctic...     

Mineral Grains of Base and Precious Metals in the Surface Layer of Bottom Sediments in the Chukchi Sea

Data on electron microprobe X-ray analysis of mineral grains of base (Cu, Zn, Sn, Pb, Ni, Bi, and Mo) and precious metals (Ag, Au, Pd, and Pt) detected for the first time in the sediments of the Chukchi Sea are presented. The peculiarities of the morphology and chemical composition of the grains are considered along with their sources and distribution in the sediments.     

Three-Dimensional Simulation of Water Circulation in the Java Sea: Influence of Wind Waves on Surface and Bottom Stresses

A one-year simulation of tide- andwind-driven circulation in the Java Sea, which is one ofthe Indonesian seas located in a tropical area, hasbeen carried out using a three-dimensionalhydrodynamic model incorporating the influence of thewind waves generated at the sea surface. This area isinfluenced by the monsoon climate (east- andwest-monsoon). Six hourly-wind fields at 10 m abovethe sea surface were used as a representative windfield. In other respects, the effect of waves on thethree-dimensional hydrodynamic model has beenrepresented by the surface and bottom stresses. Athird-generation wave model called WAM (WAMDI, 1988)was used to calculate the wave parameters and thewave dependence of the drag coefficient. Thetrajectory of water particles induced by thecalculated velocity fields in the Java Sea was then simulated.In dealing with hazardous phenomena, this modelwill be extended to predict suspended sediment fluxes,particularly those relating to catastrophic changes in seabottom topography and beach erosion. It is also animportant tool for the prediction of storm surge events.     

On the diurnal ranges of Sea Surface Temperature (SST) in the north Indian Ocean

This paper describes the variability in the diurnal range of SST in the north Indian Ocean using in situ measurements and tests the suitability of simple regression models in estimating the diurnal range. SST measurements obtained from 1556 drifting and 25 moored buoys were used to determine the diurnal range of SSTs. The magnitude of diurnal range of SST was highest in spring and lowest in summer monsoon. Except in spring, nearly 75–80% of the observations reported diurnal range below 0.5°C. The distributions of the magnitudes of diurnal warming across the three basins of north Indian Ocean (Arabian Sea, Bay of Bengal and Equatorial Indian Ocean) were similar except for the differences between the Arabian Sea and the other two basins during November–February (winter monsoon) and May. The magnitude of diurnal warming that depended on the location of temperature sensor below the water level varied with seasons. In spring, the magnitude of diurnal warming diminished drastically with the increase in the depth of temperature sensor. The diurnal range estimated using the drifting buoy data was higher than the diurnal range estimated using moored buoys fitted with temperature sensors at greater depths. A simple regression model based on the peak solar radiation and average wind speed was good enough to estimate the diurnal range of SST at ∼1.0 m in the north Indian Ocean during most of the seasons except under low wind-high solar radiation conditions that occur mostly during spring. The additional information on the rate of precipitation is found to be redundant for the estimation of the magnitude of diurnal warming at those depths.