Phytoplankton and chlorophyll a relationships with ENSO in Prydz Bay,East Antarctica

The historical data of phytoplankton and chlorophyll a(Chl a)(1990–2002)obtained during the Chinese National Antarctic Research Expedition(CHINARE)in the Prydz Bay have been integrated.The results showed that the temperature,salinity,nutrients,and oxygen of seawater changed when El Nino/La Nina occurred.The variation of biological communities reflected the response of ecosystem to environmental changes.During El Ni?o period,Chl a concentration and phytoplankton community structure changed significantly,and the relative proportion of diatoms increased while dinoflagellates decreased.During La Ni?a period,the proportion of diatoms decreased,but the golden-brown algae and blue-green algae increased significantly.The variation of phytoplankton population directly affected the biodiversity of the bay,which were also quite sensitive to the marine environment changes.Meanwhile,the satellite remote sensing data of 2002–2011(December–March)have been used to study the temporal connection change of Chl a and phytoplankton in the Prydz Bay.We found that there were significant differences in the monthly variation characteristics of satellite remote sensing Chl a and sea surface temperature(SST),which had some links with sea ice melting and El Ni?o/La Ni?a events.We found that the start time of bloom advanced,lagged or synchronized with the changes of the SST,and we also found the occurrence time of phytoplankton bloom corresponded with the sea ice melting inner bay.To some extent,this study will help us understand the relationships between ENSO events and the phytoplankton bloom in the Southern Ocean.     

The variation of temperature with time and hydrocarbon maturation in sedimentary basins formed by extension

When a sedimentary basin is formed by extension both the subsidence history and the temperature gradient can be calculated. Hence the time-temperature history of any stratum can be obtained. Three types of behaviour occur. The temperature of material which never reaches depths greater than about 4 km increases at all times. The time-temperature history of material which finally sinks to greater depths reaches a maximum during the subsidence history. The time at which this maximum occurs decreases as the depth increases. At greater depths the maximum temperature occurs at the time the basin is formed. The time-temperature history is then used to calculate Lopatin's maturation index for each stratum as a function of time, and the index plotted as a function of depth and time for different amounts of extension. The maximum temperature at a given depth, and hence Lopatin's index, is almost independent of the amount of extension when the age of the basin is greater than about 150 Ma. Similar calculations taking account of sediment compaction show the same behaviour, though the maturity of the material at a given depth is increased. Because both Lopatin's index and its calibration are empirical it is important to develop new maturation indices based on individual molecular reactions whose activation energies can be determined in the laboratory.     

Reverse time migration of CMP-gathers an effective tool for the determination of interval velocities

One of the most important steps in the conventional processing of reflection seismic data is common midpoint (CMP) stacking. However, this step has considerable deficiencies. For instance the reflection or diffraction time curves used for normal moveout corrections must be hyperbolae. Furthermore, undesirable frequency changes by stretching are produced on account of the dependence of the normal moveout corrections on reflection times. Still other drawbacks of conventional CMP stacking could be listed.One possibility to avoid these disadvantages is to replace conventional CMP stacking by a process of migration to be discussed in this paper. For this purpose the Sherwood-Loewenthal model of the exploding reflector has to be extended to an exploding point model with symmetry to the lineP _EX M whereP _EX is the exploding point, alias common reflection point, andM the common midpoint of receiver and source pairs.Kirchhoff summation is that kind of migration which is practically identical with conventional CMP stacking with the exception that Kirchhoff summation provides more than one resulting trace.In this paper reverse time migration (RTM) was adopted as a tool to replace conventional CMP stacking. This method has the merit that it uses the full wave equation and that a direct depth migration is obtained, the velocityv can be any function of the local coordinatesx, y, z. Since the quality of the reverse time migration is highly dependent on the correct choice of interval velocities such interval velocities can be determined stepwise from layer to layer, and there is no need to compute interval velocities from normal moveout velocities by sophisticated mathematics or time consuming modelling. It will be shown that curve velocity interfaces do not impair the correct determination of interval velocities and that more precise velocity values are obtained by avoiding or restricting muting due to non-hyperbolic normal moveout curves.Finally it is discussed how in the case of complicated structures the reverse time migration of CMP gathers can be modified in such a manner that the combination of all reverse time migrated CMP gathers yields a correct depth migrated section. This presupposes, however, a preliminary data processing and interpretation.     

On the automatic interpretation of direct current resistivity soundings

A method for the automatic inversion of resistivity soundings is presented. The procedure consists of two main stages. First, application of linear filters which transforms the apparent resistivity curve into the kernel function, and vice versa. In the second stage the first and second derivatives of the kernel function are calculated and used in a second-order modified Newton-Raphson iterative fitting procedure. The model obtained is optimal in the least squares sense. The method has been tried on some field examples and produced resistivity models which show a good agreement with the geological well logs.     

The orientation of the stress axes within sinking slabs

In principle it should be possible to obtain information about the orientation of the stress axes within a sinking slab from the first motions observed at a single suitably placed seismic station. This idea is tested on the Tonga-Fiji-Kermadec Arc, using the short-period vertical seismograms from Port Moresby, and the orientations so obtained agree with those derived from fault plane solutions.     

Vertical concentration profile of nonuniform sediment

A new formula for the concentration profile of nonuniform sediment is derived using the diffusion differential equation with equilibrium bed concentration.The interaction coefficient for nonuniform sediment particles as a function of both relative diameter and geometric standard deviation of nonuniform sediment is taken into account in the settling velocity.The diffusion coefficient is obtained from the logarithmic velocity profile.This new formula possesses several advantages as follows:(1)avoids theoretical defect of the Rouse formula,which states that the sediment concentration is infinite at the bottom and zero at the water surface.(2)suitable for an arbitrary fraction of nonuniform sediment,and(3)easy to apply with a simple form.The formula yields less difference among concentration profiles for various particles than that for uniform sediment and reveals the lawfor fractional concentration distribution of nonuniform sediment.The calculated concentration agrees well with the measured data from the Yangtze River.     

陕西地震应急通信指挥车改造和系统集成的关键技术研究

针对"十五"地震现场卫星集成箱系统的诸多缺点,陕西省地震局进行了应急通信指挥车的车辆改造,将地震现场通信设备安装于应急车内,并对各业务系统进行了设计集成,提升了地震现场通信保障和应急指挥能力。本文介绍了地震应急通信指挥车改造和系统集成的关键技术及实际应用情况,分析了应急通信指挥车的优势,总结了实际应用中出现的问题并提出了解决方案。     

分析云南地震资料给出的近震震级ML和面波震级Ms

云南省区域数字地震遥测台网自1999年建成以来,记录了大量地震波形资料,从2000年1月至2006年2月,云南省及邻区共发生ML≥4.0地震168次,对这些地震的震级重新进行了测定,结果表明,对于云南省的区域地震,近震的体波震级ML和面波震级MS之间不满足昆明地震台网多年使用的MS=1.13ML-1.08这一换算公式,且发现ML也不一定大于MS。     

低频检波器频谱补偿算法建模及仿真

采用数值仿真的方法建立了动圈式检波器的仿真模型,推导检波器传递函数,通过对实际动圈式检波器频率特性的测试,验证了动圈式检波器数值仿真模型的正确性,分析动圈检波器频率响应特性,分别对动圈式检波器的自然频率、灵敏度、阻尼比进行仿真,对不同自然频率、灵敏度、阻尼比对检波器输出频率特性的影响进行了分析,使用二阶二次型反馈补偿方法,设计检波器低频补偿结构,结果表明：数值仿真模型与实际检波器的频率响应一致,补偿结构使检波器自然频率由2 Hz降低至0.2 Hz.