Research On Precursory Seismic Wave Propagation Mechanism And Detection Methods Of Low Altitude Flying Targets

Radar detection,sound detection,light detection,infrared detection and other technologies are the main technical means for detecting flying targets.However,the existing technology detects low-altitude and high-speed flying targets due to interference such as surface clutter and environmental noise,so that the above technologies have many problems such as easily interfered by surface clutter and easy obstruction by obstacles when detecting flying targets,and it is difficult to accurately and timely detect target signals.Therefore,a new flying target detection technology is needed to supplement the shortcomings of the current detection technology and improve the accuracy of flying target detection.The application of seismometers to detect surface and underground targets has been widely used,and in recent years,with the study of acoustic-seismic coupling phenomenon,the research on the use of seismometers to detect flying targets has gradually developed.The seismic wave signal of the flying target is divided into precursory seismic wave and acoustic coupling wave.Research on the theoretical propagation of precursory seismic waves of flying targets.In some studies,close range observations have been achieved on artificial aircraft such as jets and helicopters.This article mainly focuses on the theory and technology of detecting flying targets such as jet aircraft that do not have obvious source characteristics and have weak energy.It discusses the applicable scenarios and detection advantages of precursor seismic wave detection technology.The seismic wave signals caused by flying targets are divided into precursory seismic waves and acoustic coupled waves,which are seismic waves excited by flying target noise and propagated along different paths.At present,the observation and recording of seismic signals on flying targets are mainly limited to acoustic coupled waves,which propagate mainly in the air and coupled above the sensor,and the propagation speed is similar to the speed of sound.The precursory seismic wave signal starts from the sound source,couples near the ground projection point of the sound source,and continues to propagate in the form of seismic waves,which is detected by buried seismometers to achieve the detection of flying targets.precursory seismic waves mainly propagate underground,which has the advantages of fast propagation speed,slow attenuation rate and weak environmental noise.The flying target detection technology based on precursory seismic wave can detect the flying target earlier,so this paper proposes the theory and detection method of precursory seismic wave propagation of flying target.Although the detection distance of hundreds of kilometers has been achieved in the observation of large energy sound sources such as meteor explosions and the detection of aura seismic waves,due to the energy problems of the sound source signal of the flying target and the complexity of the geological situation,there are still many problems to be solved in the research of flying target detection technology based on precursory seismic waves:(1)The signal energy of the precursory seismic wave of the sound source is weaker than that of the acoustic coupled wave,and the current research has less understanding of the propagation law of the precursory seismic wave,and there is a lack of theoretical research on the relevant precursory seismic waves of flying targets(2)The multi-path waves caused by the flight target,especially acoustic coupled waves and precursory seismic waves,will be aliased in the time domain,and the precursory seismic wave signal of the artificial flying target has not been observed,and the relevant precursory seismic wave interference theory is lacking.(3)The detection distance of the precursory seismic wave of the flying target is related to environmental noise.The air coupled noise affects the detection accuracy of the precursory seismic wave,and weakens the detection ability of the precursory seismic wave of the flying target.In view of the above problems,this paper focuses on the propagation theory of precursory seismic waves,the detection of precursory seismic waves of flying targets and the improvement of signal quality,etc.,and carries out the research on the propagation mechanism and detection methods of precursory seismic waves of flying targets,the main contents are as follows:Basic theory of precursory seismic wave propagation of flying targets.In order to understand the propagation law of precursory seismic waves and the performance of detection technology of flying targets,the advantages of precursory seismic wave detection compared with acoustic detection of flying targets are compared from the attenuation characteristics of precursory seismic waves.Secondly,the flying target detection model is established,the numerical solution of the propagation path of the precursory seismic wave is calculated,and the scenarios and advantages suitable for the precursory seismic wave detection are analyzed.Finally,based on the wave equation,the polarization characteristics of the precursory seismic wave of the flying target are analyzed,which provides a theoretical basis for the subsequent detection technology.Precursory seismic wave time dislocation interference theory for flying targets.After solving the propagation path of the precursory seismic wave of the flying target,it is found that the precursory seismic wave signal and the acoustic coupled wave signal at different moments of the flying target interfere in the time domain,and this interference signal changes the spectral and time domain characteristics of the signal.In this paper,a precursory seismic wave interference model of flying target is proposed,the conditions of precursory seismic wave interference and the main influencing factors of the interference model are analyzed,and the precursory seismic wave interference characteristics of flying target are explored.Precursory seismic wave detection method based on sparse representation;Since there is no precursory seismic wave observation record of the flying target,the polarization model and time domain model of the acoustic-seismic coupling wave of the flying target are first established,which provides a data basis for verifying the extraction technology of the precursory seismic wave.The sparse transform can distinguish according to the different morphological components of precursory seismic waves and acoustic coupled waves,so the selection criteria and performance comparison of the sparse dictionary of precursory seismic waves and acoustic coupled waves are discussed,and the precursory seismic wave signal of the flying target is effectively extracted by applying the precursory seismic wave extraction method based on sparse representation.Research on noise suppression method of acoustic-seismic coupling wave of flying target;The signal energy of the flying target is weak and easily drowned out by noise,so a noise suppression method is proposed for the main noise in precursory seismic wave detection.After the basic analysis of the signal detection complexity of flying targets,a spike noise suppression method based on adaptive weighting of variable window is proposed.This method not only accurately detects and suppresses the spike noise,but also preserves the characteristics of the signal.Wave noise is also a common noise in seismic signals,with low frequency,strong energy and long propagation distance.Based on this,a single-frequency noise suppression technique based on SS-PCA is proposed to suppress wave noise and other single-frequency noise and improve signal quality.In this paper,a set of evaluation criteria for air coupled wave denoising is proposed,and the mathematical relationship between signal quality and acoustic-seismic coupling transfer function is established in the standard to evaluate the reliability of the denoising method.In summary,this paper studies the precursory seismic wave detection technology for flying targets from both theoretical and application aspects,and discusses the feasibility of detection methods.In this paper,the propagation theory of precursory seismic waves based on flying targets is proposed for the first time,and the application scenarios suitable for precursory seismic wave detection and the single-station detection distance of jet aircraft are demonstrated,which provides a theoretical basis for precursory seismic wave detection of flying targets.The precursory seismic wave interference theory of flying targets is proposed,and a converging precursory seismic wave extraction algorithm based on sparse transform is proposed for interfering precursory seismic waves,so as to realize the detection of flying targets based on precursory seismic waves.Spike noise suppression technology based on variable window adaptive weighting and single-frequency noise suppression technology based on SS-PCA were proposed in the environment,respectively,which improved the signal quality of the precursory seismic wave of the flight target.