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1.
由于地震波的持续时间随震中距的增大而变长,所以主震后发生的余震事件有时因地震叠加而难以识别甚至被完全淹没,造成地震编目中的地震事件遗漏。以2014年鲁甸6.5级地震为例,通过对比不同震中距上不同仪器记录到的地震波,认为近震源区的强震记录对于识别叠加的强余震具有特别的优势。在此基础上,从震源区强震记录数据中识别并检测出主震后被淹没的两次强余震事件,震级分别为M4.6、M3.6。 相似文献
2.
ZHAO Wei WANG Hongbo GENG Jianning HU Wenmei ZHANG Zhanshuo ZHANG Guangyu 《中国海洋大学学报(英文版)》2022,21(1):28-38
Maritime transportation has become an important part of the international trade system.To promote its sustainable de-velopment,it is necessary to reduce the fuel consumption of ships,decrease navigation risks,and shorten the navigation time.Ac-cordingly,planning a multi-objective route for ships is an effective way to achieve these goals.In this paper,we propose a multi-ob-jective optimal ship weather routing system framework.Based on this framework,a ship route model,ship fuel consumption model,and navigation risk model are established,and a non-dominated sorting and multi-objective ship weather routing algorithm based on particle swarm optimization is proposed.To fasten the convergence of the algorithm and improve the diversity of route solutions,a mutation operation and an elite selection operation are introduced in the algorithm.Based on the Pareto optimal front and Pareto optimal solution set obtained by the algorithm,a recommended route selection criterion is designed.Finally,two sets of simulated navigation simulation experiments on a container ship are conducted.The experimental results show that the proposed multi-objective optimal weather routing system can be used to plan a ship route with low navigation risk,short navigation time,and low fuel consumption,fulfilling the safety,efficiency,and economic goals. 相似文献
3.
停泊船空间分布规律挖掘,在海事监管、港口管理和航运公司船队管理方面有着重要意义。现有研究主要针对船舶停泊点进行空间聚类以识别码头和锚地,缺乏对码头、锚地内船舶停泊特征分析,及码头和锚地外的异常停船的检测。因此,利用海量船舶自动识别系统（AIS）数据探索船舶停泊规律显得很有必要,且具备可行性。根据海况设定停泊速度阈值和停泊位置变化量阈值,建立停船判定模型。按港区、船型筛选,获取2016年1至11月外高桥港区集装箱船停泊记录。根据类中心点密度和聚类数量,设定邻域半径（ε）和邻域密度（MinPts）,采用密度聚类（DBSCAN）算法对船舶停泊点进行密度聚类,并将聚类结果与外高桥港区码头、锚地分布图进行比较,生成可疑停船列表。对比船舶历史轨迹,明确可疑停船列表中船舶真实停泊记录,筛选出异常停船。研究发现,2016年1至11月外高桥港区船舶异常停泊点位于圆圆沙锚地至吴淞口锚地间的南港水道和江亚南沙锚地附近的南港水道航段。船舶停泊前、后位置变化幅度小,而速度变化幅度大,推测船舶突发故障是其异常停泊的原因。海事主管部门（MSA）可根据船舶水上移动通信业务识别码（MMSI）快速锁定航运公司,加强岸上船舶安全管理。船舶停泊位置和时间能够记录船舶发生故障地点及其持续时间,为船队管理提供重要依据。 相似文献
4.
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5.
Reverse Time Migration(RTM) is a high precision imaging method of seismic wavefield at present,but low-frequency noises severely affect its imaging results.Thus one of most important aspect of RTM is to select the proper noise suppression method.The wavefield characteristics of the Poynting vector are analyzed and the upgoing,downgoing,leftgoing and rightgoing waves are decomposed using the Poynting vector of the acoustic wave equation.The normalized wavefield decomposition cross-correlation imaging condition is used to suppress low-frequency noises in RTM and improve the imaging precision.Numerical experiments using the Mamousi velocity model are performed and the results demonstrate that the upgoing,downgoing,leftgoing and rightgoing waves are well decomposed using the Poynting vector.Compared with the normalized cross-correlation imaging and Laplacian filtering method,the results indicate that the low-frequency noises are well suppressed by using the normalized wavefield decomposition cross-correlation imaging condition. 相似文献
6.
Full waveform inversion is a fitting process based on full seismic wave field simulation data using the full waveform information in seismic records and theoretically it is the ultimate goal of seismic inversion.Howev-er, there are many problems to be solved in practical application.Firstly, it is the strong nonlinear problem be-tween the seismic wave field and inversion parameters;secondly, the lack of low-frequency information in seis-mic records.In this study, the envelope is used as objective function inversion to provide the inversion result for the multi-scale full waveform inversion as the initial model, solving the lack of low-frequency information in seismic records.Taking the envelope of seismic records as the objective function in combination of multi-scale full waveform inversion became a new inversion strategy, which naturally achieved the compensation of shortage of low-frequency information and inversion from low frequency to high frequency, reducing the non-linearity in the inversion process.The comparison of the result of full waveform inversion of the initial model built through envelope inversion with the result of the conventional multi-scale full waveform inversion indicates the effective-ness of envelope inversion for the recovery of low-frequency information in seismic records. 相似文献
7.
海洋渔业是高风险行业,各类海洋灾害频繁发生,海上航行、作业环境复杂,因此,海上快速救援对保护渔民的生命财产安全具有重要意义。本文基于空间剖分的格网化编码,提出一种根据有效救援距离和失事船舶位置进行邻域搜索以查找失事船只相邻和最邻近可供救援的船只的方法,其中有效救援距离通过救援船舶的类型和航速来设定,根据有效救援距离设置不同的编码搜索长度。本文将模拟实验区域设定为我国东海海域,随机生成1×104个船位点,在时间检索效率和内存占用两方面,实验结果表明,与传统的船舶间距离的计算方法相比,基于格网化邻域搜索的查询方法编码后船位数据较编码转换前船位数据占用内存空间减少56.47%,同时,编码后检索运算的用户时间是编码前用户时间的17.67%,因此,基于格网化邻域搜索的查询方法占用内存小,且运算效率较高,能够有效提升对遇险船舶邻域救援船只的查询效率。 相似文献
8.
针对传统海浪建模方法中存在海洋表面真实感差、计算复杂的问题,本文进行了基于光滑粒子流体动力学算法（SPH）与移动立方体算法（MC）相结合的海浪建模仿真研究。通过基于空间网格的粒子分配,建立了粒子群单向列表存储结构,在海浪粒子物理量计算时,实现了其光滑核半径内粒子群的快速检索,并基于拉格朗日流体控制方程,进行了海浪粒子受力分析及状态计算;在模拟海浪与环境障碍物碰撞时,将碰撞问题简化为粒子在一定时间段内所经过的路径与障碍物表面三角面片是否相交来进行判定,并假设粒子为理想刚体,采用改进的欧拉方法实现了粒子新位置的动态计算;为增强海浪流体模拟的真实感,在移动立方体节点密度动态计算基础上,依据确定的海浪表面密度阈值,耦合MC算法进行了海浪表面的动态提取,从而实现了海浪三维表面建模与动态演变仿真。通过模拟验证了该算法的时效性与可行性,可为海洋环境信息三维可视化提供一定的参考。 相似文献
9.
In the framework of 3D potential flow theory, Bessho form translating-pulsating source Green’s function in frequency domain is chosen as the integral kernel in this study and hybrid source-and-dipole distribution model of the boundary element method is applied to directly solve the velocity potential for advancing ship in regular waves. Numerical characteristics of the Green function show that the contribution of local-flow components to velocity potential is concentrated at the nearby source point area and the wave component dominates the magnitude of velocity potential in the far field. Two kinds of mathematical models, with or without local-flow components taken into account, are adopted to numerically calculate the longitudinal motions of Wigley hulls, which demonstrates the applicability of translating-pulsating source Green’s function method for various ship forms. In addition, the mesh analysis of discrete surface is carried out from the perspective of ship-form characteristics. The study shows that the longitudinal motion results by the simplified model are somewhat greater than the experimental data in the resonant zone, and the model can be used as an effective tool to predict ship seakeeping properties. However, translating-pulsating source Green function method is only appropriate for the qualitative analysis of motion response in waves if the ship geometrical shape fails to satisfy the slender-body assumption. 相似文献
10.
一种去除地震背景噪音的新方法 总被引：1，自引：1，他引：0
杨光亮 《大地测量与地球动力学》2011,31(4):90-93
结合希尔伯特-黄变换方法,根据信号背景噪音时间延续性假设,提出了一种自适应地震信号去噪算法。利用该算法实现了台站地震监测信号的去噪分析。分析表明：1）该去噪算法能根据背景信号特性有效去除信号的低频干扰;2）该算法可自适应完成信号分解去噪,计算效率高,无时间分辨率和频率分辨率问题;3）该算法处理高频干扰存在缺陷,有待进一步完善。 相似文献
11.
在分析强震地震波信号幅频特性的基础上,采用GNSS信号模拟器,设计具有强震地震波特点的正弦轨迹,从载波相位原始量测数据和定位结果两个层面分别评估两款GNSS接收机（Trimble Net-R9和NovAtel OEM628）高频（50 Hz）观测的测量性能。结果表明,在地震波高频动态条件下,两款接收机的载波相位和定位结果都出现了明显误差,测量精度随正弦运动频率的增加而恶化,Trimble Net-R9接收机尤甚。 相似文献
12.
利用高频GPS数据长基线双差精密定位技术,获取2011年3月日本Mw9.0强震近场和远场GPS连续参考站的瞬时动态形变。分析表明：距震源较近的IGS站（USUD）的同震动态形变水平方向幅度超过60 cm,震后水平形变达到30 cm;位于远场的GPS连续参考站（JLYJ）的动态形变,清晰地给出了地震面波引起的地表形变波形。对JLYJ站的谱分析表明,地震面波引起的动态形变周期为10～17 s,并出现了两次峰值,东西向和垂向上的动态位移量远大于北南向,说明JLYJ站的形变主要由Rayleigh波及其谐波所主导,Rayleigh波的传播速度为3.5 km/s,波长约50 km。 相似文献
13.
2007-01～2014-12湖北及其周边300 km范围内共发生ML≥3.0地震306次,对其中180个地震波形的近震震级、体波震级和面波震级进行测定。通过对各种震级偏差分布分析发现,近震震级更适合作为湖北省的速报震级。 相似文献
14.
李志坚 《地球科学与环境学报》1988,(3)
本文研究了SV波在自由面上全反射的一些特殊现象。首先,从波动方程出发讨论了散射P、SV波的相移和反射场中P波的质点运动;然后,应用功能原理,计算了自由面上非均匀P波的能流密度,得出非均匀P波平均能流为零的一般结论。本文所得到的结论,对于各种地震波、弹性波和电磁波在两种均匀介质界面上发生的全反射,均可适用。 相似文献
15.
Laboratory experiments were conducted to investigate the evolution of interfacial internal solitary waves(ISWs) incident on a triangular barrier. ISWs with different amplitudes were generated by gravitational collapse. The ISW energy dissipation and turbulence processes were calculated as waves passed over the triangular barrier. Experimental results showed that ISWs were reflecting back off the triangular barrier, and shoaling ISWs led to wave breaking and mixing when waves propagated over the obstacle. Wave instability created the dissipation of energy as it was transmitted from waves to turbulence. The rate of ISW energy dissipation, the maximum turbulent dissipation, and the buoyancy diffusivity linearly increased with the increase in the incident wave energy. 相似文献
16.
F-K�任������������Ԥ�����������е���ֵģ���о� 总被引：1，自引：0，他引：1
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17.
《世界地质(英文版)》2016,(2):95-101
With the increasing complexity of prospecting objectives,reverse time migration (RTM)has attracted more and more attention due to its outstanding imaging quality.RTMis based on two-way wave equation,so it can avoid the limits of angle in traditional one-way wave equation migration,image reverse branch,prism waves and multi-reflected wave precisely and obtain accurate dynamic information.However,the huge demands for storage and computation as well as low frequency noises restrict its wide application.The normalized cross-correlation ima-ging conditions based on wave field decomposition are derived from traditional cross-correlation imaging condition, and it can eliminate the low-frequency noises effectively and improve the imaging resolution.The practical proce-dure includes separating source and receiver wave field into one-way components respectively,and conducting cross-correlation imaging condition to the post-separated wave field.In this way,the resolution and precision of the imaging result will be promoted greatly. 相似文献
18.
This paper presents a novel intelligent and effective method based on an improved ant colony optimization(ACO)algorithm to solve the multi-objective ship weather routing optimization problem,considering the navigation safety,fuel consumption,and sailing time.Here the improvement of the ACO algorithm is mainly reflected in two aspects.First,to make the classical ACO algorithm more suitable for long-distance ship weather routing and plan a smoother route,the basic parameters of the algorithm are improved,and new control factors are introduced.Second,to improve the situation of too few Pareto non-dominated solutions generated by the algorithm for solving multi-objective problems,the related operations of crossover,recombination,and mutation in the genetic algorithm are introduced in the improved ACO algorithm.The final simulation results prove the effectiveness of the improved algorithm in solving multi-objective weather routing optimization problems.In addition,the black-box model method was used to study the ship fuel consumption during a voyage;the model was constructed based on an artificial neural network.The parameters of the neural network model were refined repeatedly through the historical navigation data of the test ship,and then the trained black-box model was used to predict the future fuel consumption of the test ship.Compared with other fuel consumption calculation methods,the black-box model method showed higher accuracy and applicability. 相似文献
19.
港口是物流供应链中的核心环节,港口服务效率会决定整个物流供应链的效率。本文提出了一种基于海量船舶AIS（Automatic Identification System）轨迹数据的港口服务效率计算框架,利用集装箱船舶AIS轨迹、港口地理信息等海事大数据,采用滑动窗口算法等数据挖掘方法判断船舶在港内的状态,估算出反映港口服务效率的AWT/AST指标,从时间维度对港口服务效率评价,为港口管理运营部门和航运公司决策提供参考。并以上海港、宁波港、深圳港、釜山港为例,采用2018年全年全球5600余艘集装箱船舶的AIS轨迹数据,量化评价4个亚洲集装箱港口的服务效率。结果显示:① 船舶抵港泊位作业时间近似正太分布,正太分布均值在14~18 h之间,船舶泊位作业时间集中在10~30 h;② 船舶泊位作业时间与船舶船型大小成正相关,船型越大则泊位作业时间越长;③ 32%的船舶抵达上海港会发生等待时间,体现上海港集装箱码头整体处于供不应求的状态。宁波港整体服务效率较高,船舶发生等待事件较少。作为区域性枢纽港,釜山港近洋区域性运输频繁使得釜山港抵港船舶频率较高。④ 洋山四期码头为自动化码头,其港口装卸工艺与其他码头不同,但其码头作业效率并未高很多。 相似文献
20.
Magnetotelluric(MT)inversion and seismic inversion are important methods for the interpretation of subsurface exploration data,but separate inversion of MT and seismic produces ambiguous and non-unique results due to various factors.In order to achieve accurate results,the authors propose a joint inversion method of two-dimensional MT and seismic data in the frequency domain.The finite element method is used for numerical simulation of electromagnetic data in the forward modelling,and the Gauss-Newton method is used for the inversion.The 9-point-finite-difference method is used to solve the seismic wave field in the acoustic wave equation,and the inverse problem of seismic data is solved by full waveform inversion with a conjugate gradient,a simple and fast method.Cross gradient functions are used to provide constraint structure between resistivity and velocity parameters to carry out the joint inversion.The joint inversion algorithm is tested by double-rectangular model synthesis data,and the accuracy of the algorithm is verified.The results show that the joint inversion results are better than those from separate inversion.The algorithm is applied to a geophysical model of a metalliferous deposit in Jinchuan and is compared with the separate inversion results.It shows that the results obtained with joint inversion are much closer to the real model. 相似文献