Research On Infrasound Localization Method Based On Wide Area Monitoring Network

Infrasound is one of the important physical effects of nuclear explosion.It has the characteristics of low frequency,small attenuation and long propagation distance in the atmosphere.It is the main detection method for remote nuclear explosion monitoring.The Comprehensive Nuclear Test Ban Treaty lists infrasound technology as one of the four detection technologies of the International Monitoring System.This technology can not only monitor atmospheric nuclear explosions,but also can be used to monitor underwater nuclear explosions and shallow underground nuclear explosions.The wide-area infrasound monitoring network can not only monitor nuclear explosions,but also monitor large-scale infrasound events such as chemical explosions,rocket launches,earthquakes,and exploding volcanoes.How to determine the location of the source term of infrasound events according to the infrasound monitoring data is one of the important research contents of the infrasound monitoring signal processing technology.Therefore,this paper studies the infrasound localization method of the wide-area monitoring network.The main work and conclusions of the paper are as follows:(1)Research on infrasound signal preprocessing method.Aiming at the problem that the measured signal contains noise interference,a digital Butterworth filter of0.001 Hz ～ 20 Hz is designed to realize the noise reduction and filtering of the infrasound signal,which is the basis for accurately calculating the delay amount and improving the positioning accuracy.Perform spectrum analysis on the filtered infrasound signal to obtain the characteristic frequency parameters of various infrasound source signals,which are used for the selection of single-station infrasound directional model.(2)Research on single-station infrasound orientation method.Taking the infrasound signal launched by the rocket as an example,the short-term energy mutation algorithm is used to calculate the time difference of the infrasound signal.According to the power spectrum distribution characteristics of the rocket launch infrasound signal and the distance parameters of the monitoring array elements,it is judged that the rocket launch infrasound event is in the near-field range,and a single-station near-field infrasound localization method is proposed.The short-term energy mutation delay estimation algorithm is used for orienting and measuring the rocket launch event,the orientation error is within 2°,the distance error is about 3.17%,and the positioning accuracy is higher.In addition,the short-term energy mutation time delay estimation algorithm is used to conduct directional analysis and research on chemical explosion infrasound signals and multi-station infrasound signals of Tonga volcanic eruption.For the chemical explosion test,the approximate orientation of the chemical explosion event was obtained by using the binary array far-field directional model.Using the monitoring data of 16 international infrasound stations to orient the volcanic eruption event,the orientation error is small,which provides a better data basis for the subsequent event location.(3)Research on cross location of multi station direction.Aiming at the problem that cross location of multi station direction cannot be exactly at one point,this paper deduces the method of multi station direction finding and positioning based on the least squares.The localization accuracy of the built wide-area infrasound network distributed in four regions is evaluated,and the influence of infrasound sources at different locations on the localization results is discussed respectively.When the infrasound source is in the monitoring station,the least squares are used to optimize the localization error.When the infrasound source is outside the monitoring station(and the infrasound signals received by the two monitoring stations have basically the same direction of arrival),the analysis of the positioning results shows that the positioning estimation error is relatively large.Finally,the method of multi station direction finding and positioning is used to analyze infrasound signal of the chemical explosion and Tonga volcanic eruption.The positioning error of the two-station intersection for the chemical explosion test event is about 3 km.The K＿means clustering algorithm was used to eliminate the data with large intersection errors in 16 incoming wave directions,and then the least squares were used to optimize the positioning.The error of cross location of multi station direction for Tonga volcano eruption is about 102 km,and the average distance error between the positioning result and each monitoring station is about 1.29%,and better positioning results are obtained.In this paper,the short-term energy mutation algorithm is used to calculate the time difference between the infrasound signals arriving at the array elements,and a single-station infrasound orientation and multi-station direction finding intersection location method based on the time difference has been studied.Algorithms such as short-term energy mutation delay estimation,K＿means clustering and least squares optimal localization have been successfully applied to infrasound localization in wide-area monitoring networks,which can provide key technical support for solving the localization of infrasound events.