【摘要】 利用1995年至2009年中国东北及邻近地区11个宽频带台站记录到的77个地震事件、3个化学爆炸和2次朝鲜核爆的区域地震资料,标定该区域台网的Rayleigh波震级.通过对8～25s周期的垂直分量Rayleigh波形进行分析,获取基于最大振幅的面波震级.计算82个区域事件不同周期的台基响应,经过台基校正后取最大振幅的面波震级为事件震级.2006年和2009年两次朝鲜核爆的面波震级分别为2.93±0.19和3.62±0.21.将地震和核爆事件的面波震级Ms与体波震级mb(Lg)进行比较,发现根据该区域台网的数据利用Ms-mb识别方法无法鉴别朝鲜地区的核爆与地震.朝鲜核爆的面波震级相对较大,使Ms-mb识别方法失效,其原因可能是源区介质的不均匀性、由核爆炸冲击引发的深部的拉伸破坏被抑制,或者是近爆源区存在张性的构造预应力.假定核爆可能的埋藏深度范围是0.01～1.0km,用Rayleigh波震级估计朝鲜核爆的当量,对2006年和2009年核爆当量的估值范围分别为0.42～3.17kt和2.06～15.53kt.更多还原

【Abstract】 We collect regional seismic data recorded at broadband seismic stations from 77 earthquakes,3 chemical explosions and 2 nuclear explosions between 1995 and 2009 in Northeast China and its vicinity.These data are used to calibrate the regional seismic network for measuring the Rayleigh-wave magnitude.Based on vertical-component Rayleigh wave records between 8 and 25 s,we obtain the maximum-amplitude surface-wave magnitudes.Using records from 82 events,we calculate the site corrections at different period for all stations.After removing the site response,we obtain the Rayleigh-wave magnitude for individual station-event pair.Finally the network average magnitude is obtained for each event.The Rayleigh-wave magnitudes are 2.93±0.19 and 3.62±0.21 for 2006 and 2009 North Korean nuclear explosions.The comparison between the Rayleigh-wave magnitude Ms and the body wave magnitude mb(Lg) suggests that Ms-mb method is invalid in discriminating the nuclear explosions from earthquake populations in Northeast China/North Korea region and within the regional distances.The two North Korean nuclear explosions excited strong Rayleigh waves,leading to the poor performance of Ms-mb discrimination.The possible reasons include near-source heterogeneities,asymmetric source or existing tensile tectonic release.Given the depth of burial between 0.01 and 1.0 km and using the obtained Rayleigh-wave magnitudes,the yields of the 2006 and 2009 North Korean nuclear tests are estimated to be 0.42~3.17 kt and 2.06~15.53 kt,respectively.更多还原