中国东北和朝鲜半岛地区地壳Lg波宽频带衰减模型

摘要

利用1996年10月至2016年10月间发生在中国东北、朝鲜半岛和日本南部的113个壳内地震在602个宽频带地震台站观测到的波形资料,建立Lg波衰减成像数据集.根据22,551条垂直分量波形,计算Lg波振幅谱,提取单台、双台和双事件数据,采用区域Q值、震源函数和台基响应联合反演方法,建立中国东北和朝鲜半岛地区0.05～10.0 Hz的宽频带衰减模型.模型显示火山岩山脉地区如大兴安岭和长白山具有弱衰减特征,沉积盆地衰减相对较强,海水覆盖区域如渤海、黄海和日本海等衰减最强.日本海具有较薄的海洋地壳,对地壳Lg波传播有阻挡作用.通过较大地震事件的跨海记录调查Lg波的传播,强衰减特征最为显著.%Lg wave propagation characteristics are investigated in Northeast China and the Korean Peninsula based on seismograms from 113 crustal earthquakes that were recorded at 602 regional stations distributed throughout eastern China,South Korea,and southern Japan.Based on 22,551 verticalcomponent waveforms,we calculate the amplitude spectra of the Lg waves,extract the singlestation,two-station,and two-event data,and construct a broadband Lg attenuation model between 0.05 and 10.0 Hz in Northeast China and the Korean Peninsula by using a joint tomographic method to simultaneously obtain Q,source function,and site response.Results show that the sedimentary basin areas are characterized by relatively strong Lg attenuation,whereas the volcanic mountains such as Da Hinggan Ling and Changbai mountains attenuate the Lg waves weakly.The strongest Lg attenuation regions are areas covered by sea water including Bohai Sea,Yellow Sea and Japan Sea.A thinner crust within a typical oceanic lithosphere for the Japan Sea blocks the Lg wave propagation,resulting in no signals can be observed across oceanic path from small earthquakes.We collect observations from large earthquakes with magnitude around mb 6.0 to obtain strong Lg attenuation within the crust of Japan Sea.