星载电场数据处理方法研究

给出一种新的非线性、非平稳信号的处理方法——HHT方法,并把该方法首次应用于星载电场数据处理中.以2004年9月15日菲律宾6.0级地震前两天(13日)DEMETER卫星经过震中区域上空所记录到的数据为例,对ULF频段的电场数据进行了处理,得到了相应的HHT时频图谱.另外,还利用DEMETER卫星中心网站提供的SWAN软件计算得到了相应的小波变换时频图谱,通过比较发现,虽然两种方法对异常信号出现的位置时刻的描述有相同的能力,但HHT方法在异常信号的细节描述上更为清晰,从而为今后进一步的研究工作奠定了基础.     

地震电磁卫星交变电磁场的数据处理

地震电磁卫星的迅速发展也带来了一些相关的研究课题,本文根据地面地震电磁观测中成熟的监测手段和参数,来分析如何根据地震电磁卫星记录的电、磁场分量提取可能与地震电磁异常现象有关的信息.介绍了电磁场时间序列的幅值统计;电磁波谱尤其是自功率谱对噪音干扰敏感,介绍了自功率谱的计算方法;正交电磁场相关度的变化分析方法;空间电磁波平面特征指标求取;以及在简单平面波特征下,提出空间阻抗张量的计算方法.     

Magma discharge variations during the 2011 eruptions of Shinmoe-dake volcano, Japan, revealed by geodetic and satellite observations

We present precise geodetic and satellite observation-based estimations of the erupted volume and discharge rate of magma during the 2011 eruptions of Kirishima-Shinmoe-dake volcano, Japan. During these events, the type and intensity of eruption drastically changed within a week, with three major sub-Plinian eruptions on January 26 and 27, and a continuous lava extrusion from January 29 to 31. In response to each eruptive event, borehole-type tiltmeters detected deflation of a magma chamber caused by migration of magma to the surface. These measurements enabled us to estimate the geodetic volume change in the magma chamber caused by each eruptive event. Erupted volumes and discharge rates were constrained during lava extrusion using synthetic aperture radar satellite imaging of lava accumulation inside the summit crater. Combining the geodetic volume change and the volume of lava extrusion enabled the determination of the erupted volume and discharge rate during each sub-Plinian event. These precise estimates provide important information about magma storage conditions in magma chambers and eruption column dynamics, and indicate that the Shinmoe-dake eruptions occurred in a critical state between explosive and effusive eruption.     

Processing of aerogeophysical data by PERICOLOR image processing system

The results of the last stage of an aerogeophysical survey are available on computer compatible tapes in Czechoslovakia. For the processing and interpretation, the image processing system PERICOLOR is used. In the case of aeromagnetic data, the best results are obtained by means of directional first-derivative filtering. On the other hand, with aerospectrometric data, the plotting in the form of colour composite images and ternary maps is the best way. Simultaneous presentation of different data is possible using the HSI transform. Multiple data sets (including topography and gravity) are prepared for integral processing and interpretation in some parts of Czechoslovakia.     

数字化体应变仪观测值突跳的分析

山东长清台数字化体应变仪观测曲线自1999年以来出现几次形态类似的大幅度突跳,为正确认识这类现象,在长清台做了交直流切换对观测值影响试验,并对水位、气压资料进行综合分析。研究结果表明,水位、气压、电源切换等因素不会引起体应变仪观测曲线的突跳。对比其他类似观测分析推测,这类突跳可能与“慢地震”事件或“岩孔崩落”现象有关。     

兰州观象台FSQ和SSY-Ⅱ数字资料与模拟资料的对比

2002年对兰州观象台FSQ与SSY-Ⅱ两套仪器同时进行模拟与数字记录发现,模拟记录与数字记录有着较为明显的差异。为了对比模拟记录与数字记录的优劣,对FSQ的两套观测资料进行了年趋势变化、调和分析、日均值的相对噪声水平等的对比分析,对SSY-Ⅱ的资料进行了年趋势变化、调和分析、Nakai检验等的对比分析。通过对比发现模拟记录与数字记录的差异,是由于对这两种资料的处理不一致造成的。     

Kinematics of active earthflows revealed by digital image correlation and DEM subtraction techniques applied to multi‐temporal LiDAR data

Earthflow‐type landslides are persistent natural hazards having deep socio‐economic and environmental consequences. They have significantly contributed to the geomorphic evolution of mountainous slopes in Europe since the Late Glacial. An understanding of their complex kinematics is crucial to better constrain the processes governing their occurrence and mobility. In this work we explored the possibility to quantify displacement vectors on a spatially distributed basis and to quantify volumetric transfer at the slope scale with regard to a large flow‐type landslide located in the northern Apennines of Italy. For this purpose we applied digital image correlation (DIC) and digital elevation model differencing (DEMoD) techniques to multi‐temporal airborne LiDAR surveys of 2006, 2007 and 2009. The DIC was applied to greyscale slope gradient maps retrieved after precise co‐registration of LiDAR surveys. Thereby, movement patterns over various sectors of the landslide were reconstructed and quantified, most notably up to 20 m in the head zone, up to 51 m in the lower main track, and up to about 27 m at the landslide toe. The DEMoD analysis revealed significant mass transfer from the source to the tracks and toe zone, with the upper flow tracks acting as temporal storage of large amounts of material. The mass balance indicated that significant amounts of advancing landslide debris were eroded by a local stream. An integrated analysis of DEMoD and DIC results allowed for a discussion of governing processes, such as the transition from slide to flow, the influence of underlying topography on earthflow mobility, and the role of undrained loading as a mechanism of toe zone reactivation. In conclusion, the successful application of DIC and DEMoD to the case study underlines the added value of high‐resolution DEMs in the analysis of earthflow kinematics toward a better understanding of their role in the geomorphic evolution of slopes. Copyright © 2012 John Wiley & Sons, Ltd.     

Ocean eddy momentum fluxes at the latitudes of the Gulf Stream and the Kuroshio extensions as revealed by satellite data

Eddy momentum fluxes, i.e. Reynold stresses, are computed for the latitude bands of the Gulf Stream and Kuroshio extensions using 13 years of data from the merged satellite altimeter product of Le Traon et al. The spatial pattern and amplitude of the fluxes is remarkably similar to that found by Ducet and Le Traon using the 5 years of data that were available to them. In addition to updating the work of Ducet and Le Traon, we provide new insight into the role played by the underlying variable bottom topography, both for determining the structure of the eddy momentum fluxes seen in the satellite data and for influencing the way these fluxes feedback on the mean flow. While there is no clear evidence that eddies locally flux momentum into the eastward jets of the Gulf Stream and Kuroshio extensions, a clearer picture emerges after zonally integrating across each of the North Atlantic and North Pacific basins. We argue that the eddy momentum fluxes do indeed drive significant transport, a conclusion supported by preliminary results from a 3-D model calculation. We also present evidence that in the North Pacific, the Reynolds stresses are important for driving the recirculation gyres associated with the Kuroshio extension, taking advantage of new data from both observations and high-resolution model simulations.