2020年7月12日唐山MS5.1地震预警处理能力分析     

王莉婵  毛国良  李小军  王宁  王亚玲 《中国地震》2020,36(3):394-406

2020年7月12日，河北唐山发生M_S5.1地震，河北省地震预警系统成功地处理并产出了这次地震预警各种结果数据，本文借助此次地震对河北地震预警网内震中距200km范围内台站产出质量以及地震预警前5次处理结果进行详细分析。此次地震发生在河北地震预警网内，平均台间距为10km，首台触发后3s、震后6s发布首次处理结果，与编目结果相比，震级偏差为-1.3，震中位置偏差为2.6km，盲区半径为18km。随着参与定位台站数量增多，震级与位置偏差越来越小，但震级仍整体偏小。河北地震预警网台站产出质量整体较高，其中烈度台作为地震预警最重要的组成部分，是决定预警效果的关键因素。本次地震震中距200km范围内，烈度台平均信噪比为48，震中距50km范围内平均信噪比为112，符合预警系统对信噪比的要求。本次地震预警结果表明，河北地震预警网内台站布局基本合理，波形质量较高，地震预警系统处理软件在本次地震中预警产出效果较好，已经具备了一定的地震预警能力。  相似文献   

An Automatic Method for Detecting Transients and Variable Sources in AST3 Survey Based on Image Subtraction and Random Forest     

《Chinese Astronomy and Astrophysics》2020,44(1):41-60

AST3-2 (the second Antarctic Survey Telescope) is located in Antarctic Dome A, the loftiest ice dome on the Antarctic Plateau. It produces a huge amount of observational data which require a more efficient data reduction program to be developed. Also the data transmission in Antarctica is much difficult, thus it is necessary to perform data reduction and detect variable and transient sources remotely and automatically in Antarctica, but this attempt is restricted by the unsatisfactory performance of the low power consumption computer in Antarctica. For realizing this purpose, to develop a new method based on the existing image subtraction method and random forest algorithm, taking the AST3-2 2016 dataset as the test sample, becomes an alternative choice. This method performs image subtraction on the dataset, then applies the principle component analysis to extract the features of residual images. Random forest is used as a machine learning classifier, and in the test a recall rate of 97% is resulted for the positive sample. Our work has verified the feasibility and accuracy of this method, and finally found out a batch of candidates for variable stars in the AST3-2 2016 dataset.  相似文献   

A high accurate automated first-break picking method for seismic records from high-density acquisition in areas with a complex surface     

Yinpo Xu  Cheng Yin  Xuefeng Zou  Yudong Ni  Yingjie Pan  Liangjun Xu 《Geophysical Prospecting》2020,68(4):1228-1252

As the application of high-density high-efficiency acquisition technology becomes more and more wide, the areas with complex surface conditions gradually become target exploration areas, and the first-break picking work of massive low signal-to-noise ratio data is a big challenge. The traditional method spends a lot of manpower and time to interactively pick first breaks, a large amount of interactive work affects the accuracy and efficiency of picking. In order to overcome the shortcoming that traditional methods have weak anti-noise to low signal-to-noise ratio primary wave, this paper proposes a high accurate automated first-break picking method for low signal-to-noise ratio primary wave from high-density acquisition in areas with a complex surface. Firstly, this method determines first-break time window using multi-azimuth spatial interpolation technology; then it uses the improved clustering algorithm to initially pick first breaks and then perform multi-angle comprehensive quality evaluation to first breaks according to the following sequence: ‘single trace → spread → single shot → multiple shots’ to identify the abnormal first breaks; finally it determines the optimal path through the constructed evaluation function and using the ant colony algorithm to correct abnormal first breaks. Multi-azimuth time window spatial interpolation technology provides the base for accurately picking first-break time; the clustering algorithm can effectively improve the picking accuracy rate of low signal-to-noise ratio primary waves; the multi-angle comprehensive quality evaluation can accurately and effectively eliminate abnormal first breaks; the ant colony algorithm can effectively improve the correction quality of low signal-to-noise ratio abnormal first breaks. By example analysis and comparing with the commonly used Akaike Information Criterion method, the automated first-break picking theory and technology studied in this paper has high picking accuracy and the ability to stably process low signal-to-noise ratio seismic data, has a significant effect on seismic records from high-density acquisition in areas with a complex surface and can meet the requirements of accuracy and efficiency for massive data near-surface modelling and statics calculation.  相似文献   

Three-parameter Radon transform in layered transversely isotropic media     

Mohammad Mahdi Abedi  Mohammad Ali Riahi  Alexey Stovas 《Geophysical Prospecting》2019,67(2):395-407

Radon transform is a powerful tool with many applications in different stages of seismic data processing, because of its capability to focus seismic events in the transform domain. Three-parameter Radon transform can optimally focus and separate different seismic events, if its basis functions accurately match the events. In anisotropic media, the conventional hyperbolic or shifted hyperbolic basis functions lose their accuracy and cannot preserve data fidelity, especially at large offsets. To address this issue, we propose an accurate traveltime approximation for transversely isotropic media with vertical symmetry axis, and derive two versions of Radon basis functions, time-variant and time-invariant. A time-variant basis function can be used in time domain Radon transform algorithms while a time-invariant version can be used in, generally more efficient, frequency domain algorithms. Comparing the time-variant and time-invariant Radon transform by the proposed basis functions, the time-invariant version can better focus different seismic events; it is also more accurate, especially in presence of vertical heterogeneity. However, the proposed time-invariant basis functions are suitable for a specific type of layered anisotropic media, known as factorized media. We test the proposed methods and illustrate successful applications of them for trace interpolation and coherent noise attenuation.  相似文献   

Seismic receiver coupling to the seafloor     

Marcus Landschulze 《Geophysical Prospecting》2019,67(6):1571-1581

The presence of geophysical receivers on the seafloor changes the local wave field due to the receiver seafloor interaction. The resulting PP- and PS-wave distortion of the wave field is often referred to as receiver coupling to the seafloor and can make data processing challenging and sometimes impossible. This paper provides an overview of the mathematical approaches to describe receiver coupling, how to estimate receiver coupling and what the difficulties and possible solutions are. The first section shows how the mathematical approach developed from a simple model considering only the vertical receiver component to include all three receiver components and their interactions with the seafloor. In the second section, I show how receiver coupling can be measured and how it can be improved using mathematical and data-driven approaches.  相似文献   

Mitigating the effects of sand dunes on seismic data from the Rub al Khali basin,Saudi Arabia     

Mustafa Al-Marzooq  Mamadou S. Diallo  Vincent Etienne  Thierry Tonellot  SanLinn I. Kaka 《Geophysical Prospecting》2019,67(7):1825-1837

The Rub Al Khali region in Saudi Arabia is characterized by the presence of sand dunes separated by salt flats, also called Sabkhas. In general, the elevation of dunes in this region varies between 90 and 250 m above sea level. The presence of these sand dunes, along with the rapidly changing surface topography poses challenges for seismic data acquisition and processing. The high contrast in acoustic impedance between the dune base and the underlying formation often results in amplification of seismic waves that are recorded at stations located on the surface of sand dunes. Attempts to address the issue using conventional surface-consistent amplitude scaling methods without reducing these amplification effects generally fail, thus compromising the suitability of the processed data for amplitude versus offset analysis. In this study, we propose a new reference site technique to reduce the effects of sand dune amplification, enabling the production of data sets that are suitable for amplitude versus offset processing. The proposed technique uses a deterministic approach to derive surface-consistent, frequency-dependent de-amplification functions for shots and stations located on the dunes only. Two-dimensional synthetic and field data examples show that the technique significantly reduces the effects of sand dune amplification.  相似文献   

Prediction of signatures of airgun arrays using dual near-field hydrophones     

Maksym Kryvohuz  Xander Campman 《Geophysical Prospecting》2019,67(6):1522-1546

Successful estimation of airgun-array signatures from near-field measurements depends on the accuracy of poorly controlled model parameters such as the effective sea surface reflection coefficient and source depth. We propose a method for prediction of robust source signatures, which are insensitive to fluctuations of the latter parameters. The method uses vertical pairs of near-field hydrophones to measure near-field pressure and its vertical gradient, combination of which eliminates sea surface reflections from the near-field data. This excludes the uncertainty related to the fluctuating sea state and source depth from the process of inversion of the near-field data for source signature. The method explicitly separates the recorded near-field pressure into its up and down going components, which allows one to measure the effective frequency- and angle-dependent sea surface reflection coefficient right at the source, as well as to estimate the actual source depth. Tests on synthetic and field data demonstrate robust performance of the method.  相似文献   

Intra-survey reservoir fluctuations – implications for quantitative 4D seismic analysis     

Veronica Omofoma  Colin MacBeth  Hamed Amini 《Geophysical Prospecting》2019,67(2):282-297

During the time taken for seismic data to be acquired, reservoir pressure may fluctuate as a consequence of field production and operational procedures and fluid fronts may move significantly. These variations prevent accurate quantitative measurement of the reservoir change using 4D seismic data. Modelling studies on the Norne field simulation model using acquisition data from ocean-bottom seismometer and towed streamer systems indicate that the pre-stack intra-survey reservoir fluctuations are important and cannot be neglected. Similarly, the time-lapse seismic image in the post-stack domain does not represent a difference between two states of the reservoir at a unique base and monitor time, but is a mixed version of reality that depends on the sequence and timing of seismic shooting. The outcome is a lack of accuracy in the measurement of reservoir changes using the resulting processed and stacked 4D seismic data. Even for perfect spatial repeatability between surveys, a spatially variant noise floor is still anticipated to remain. For our particular North Sea acquisition data, we find that towed streamer data are more affected than the ocean-bottom seismometer data. We think that this may be typical for towed streamers due to their restricted aperture compared to ocean-bottom seismometer acquisitions, even for a favourable time sequence of shooting and spatial repeatability. Importantly, the pressure signals on the near and far offset stacks commonly used in quantitative 4D seismic inversion are found to be inconsistent due to the acquisition timestamp. Saturation changes at the boundaries of fluid fronts appear to show a similar inconsistency across sub-stacks. We recommend that 4D data are shot in a consistent manner to optimize aerial time coverage, and that additionally, the timestamp of the acquisition should be used to optimize pre-stack quantitative reservoir analysis.  相似文献   

Research on the Application of Fast-steering Mirror in Stellar Interferometers     

Mei Rong  Hu Zhong-wen  Xu Teng  Sun Chang-sheng 《Chinese Astronomy and Astrophysics》2018,42(3):475-486

In stellar interferometers, the fast-steering mirror (FSM) is widely utilized to correct the wavefront tilt caused by the atmospheric turbulence and internal instrumental vibration, because of its high resolution and fast response frequency. In this study, the non-coplanar error between the FSM and the actuator deflection axis introduced by the manufacturing, assembly, and adjustment is analyzed systematically. Via a numerical method, the additional optical path difference (OPD) caused by the above factors is studied, and its effect on the fringe tracking accuracy of a stellar interferometer is also discussed. On the other hand, the starlight parallelism between the beams of two arms is one of the main factors for the loss of fringe visibility. By analyzing the influence of wavefront tilt caused by the atmospheric turbulence on fringe visibility, a simple and efficient real-time correction scheme of starlight parallelism is proposed based on a single array detector. The feasibility of this scheme is demonstrated by a laboratory experiment. The results show that after the correction of fast-steering mirror, the starlight parallelism meets preliminarily the requirement of a stellar interferometer on the wavefront tilt.  相似文献   

多源高分辨率DOM批量快速制作方法研究   总被引：1，自引：0，他引：1  

张亚亚  马小计  周亦 《测绘通报》2019,(7):96-99,146

随着遥感数据在自然资源调查中的广泛应用，对多源高分辨率遥感影像“一张图”批量快速制作有了更高的需求。本文以广西壮族自治区北海市银海区作为试验区，利用Pixel Engine软件的“RS+GIS+Photoshop”算法，首先，针对多源高分辨率遥感卫星数据特点，制定相应的数据处理流程，自动化制作单景DOM；然后，以县级辖区为单位，批量快速制作县级辖区DOM；最后，从制作精度和速度两个方面，将该方法制作得到的DOM成果与人工处理成果进行对比，分析该方法的可行性，提出了一种快速、有效的多源高分辨率DOM制作方法。  相似文献