利用超导重力数据检测日本M_w9.0地震的低频自由振荡及谱线分裂  

Detecting low-frequency free oscillations and split modes from Japan M_w9.0 earthquake using superconducting gravity observations

作　　者：许闯[1] 钟波[1,2] 罗志才[1,2,3] 李琼[1] 

机构地区：[1]武汉大学测绘学院,武汉430079 [2]地球空间环境与大地测量教育部重点实验室,武汉430079 [3]武汉大学测绘遥感信息工程国家重点实验室,武汉430079

出　　处：《地球物理学报》2014年第10期3103-3116,共14页Chinese Journal of Geophysics

基　　金：国家重点基础研究发展计划(973计划)(2013CB733302);国家自然科学基金项目(41131067;41174020);武汉大学地球空间环境与大地测量教育部重点实验室开放基金项目(11-02-08)资助

摘　　要：准确估计低频自由振荡及谱线分裂是约束地球内部结构和改进地球模型的重要手段.本文利用四个不同台站的超导重力观测数据系统研究了日本Mw9.0大地震激发的低于1.5mHz自由振荡及谱线分裂.研究结果表明:(1)选取适当的数据长度,超导重力观测数据可以检测出低于1.5 mHz除1S1以外的所有自由振荡;(2)除0S2、0S3、0S0、2S1、3S1、1S2和0T2外,重点探测出3S2、0S4和1S4谱线分裂的所有谱峰;(3)与PREM模型理论频率相比,0S0观测频率平均向右偏移0.354×10-3 mHz,说明PREM理论模型中地幔底部参数与真实地球可能存在微小偏差;(4)3S2的谱线分裂率r为1.485267,比PREM理论谱线分裂宽度约宽50%,表明PREM中地球内核中部介质参数可能存在一定误差,需要进一步改善.另外,quasi-0T2的r为1.254206,比PREM理论谱线分裂宽度约宽25%.It is an important method to estimate low-frequency modes and split modes precisely for constraining the structure of Earth and improving Earth model. Therefore,the free oscillations below 1.5 mHz excited by Japan Mw9.0earthquake are detected systemically from superconducting observations of four different stations in this paper.The results show that：（1）Based on appropriate length,all the free oscillations,except1S1,below 1.5mHz can be detected by superconducting observations;（2）In addition to0S2,0S3,0S0,2S1,3S1,1S2and0T2,all peaks of split for3S2,0S4and1S4 are detected particularly;（3）Compared with PREM,the observedfrequency of0S0 is bigger 0.354×10^-3 mHz.It indicates that there may be small error in the bottom of mantle for PREM;（4）The splitting ratios r of3S2 are 1.485267,about 50% times wider than PREM.It can be deduced from the results that the elastic parameters for center of inner core from PREM need to improve.In additions,the rof quasi-0T2 is 1.254206,about 25%times wider than PREM.

关 键 词：低频自由振荡 谱线分裂 日本Mw9.0地震 超导重力观测数据 

分 类 号：P312[天文地球—固体地球物理学]