【摘要】 利用布设在长白山地区临时地震台站接收到的朝鲜核爆的波形资料,对2009年5月25日和2013年2月12日两次朝鲜核试验的地震学特征进行比较.震中距范围从145km到420km.采用P/S型谱比值方法识别朝鲜核爆,通过与2009年3月20日长春地震和2013年1月23日沈阳地震事件的比较,表明在频率大于3 Hz时P/S型谱比值能够有效识别发生在中朝边境地区的地下核试验.选定参考台站,利用区域震相Pg波的振幅谱比值计算朝鲜核爆至各台站路径上的相对衰减.结合介质速度模型,在一定程度上反映了长白山地区衰减情况,为进一步研究长白山地区衰减层析成像提供初始模型.更多还原

【Abstract】 Although the UN passed"Comprehensive Nuclear-Test-Ban Treaty"as early as 1996,facing the international situation,it is also necessary to study the recognition method of nuclear explosions and to apply it to discrimination of earthquakes and nuclear explosions.In this study we make a comparison of seismic characteristics of the two North Korean nuclear tests on 25May2009 and on 12 February 2013by using the waveform data from these two events recorded by temporary seismic stations located in the Changbai Shan region and obtain the seismological characteristics of the two nuclear explosions in order to reach the aim of recognizing nuclear explosions.Because there exist obvious differences in the phase′s amplitude and frequency between nuclear tests and earthquakes,we use the method of P/S mode spectral ratios to recognize the North Korean′s nuclear explosions by using the data with epicentral distances from 145 to 420km.Amplitude spectrum ratios of regional Pg phase(waveforms of stations and selected reference stations)are used to calculate the relative attenuation factor(δt*)on the ray path between the North Korean nuclear explosion and the stations.P/S-style spectral ratios exhibit obvious disparities at frequency 3~11Hz by comparing the North Korean underground nuclear tests with the earthquakes in Changchun and Shenyang,i.e.Pn/Lg>1for nuclear explosions and Pn/Lg<1for earthquakes.The Pg/Lg spectral ratio of the2013 nuclear test is obviously larger than that of the 2009 nuclear test.In addition,the distribution ofδt*shows that the larger attenuations of stations are distributed in the southeast and nearby the Changbai Shan volcano.The closest station(in Changbai County)presents low attenuation and the farthest station(in Changchun city)presents largest attenuation.P/S-mode spectral ratios effectively discriminate North Korean underground nuclear tests at frequency above 3Hz by comparison with earthquakes.The released energy of the 2013 nuclear test is more than that of the 2009 nuclear test by comparing the amplitude spectra of the two nuclear explosions.The distribution of attenuation which reflects the attenuation structure of crust and upper mantle is related to the locations of magma chambers and consistent with the velocity model in the study area.更多还原