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Title:: Detecting the Free Oscillation of the Earth through the Observational Data of Water-tube Tiltmeters in Yunnan

作者:: 杨跃文¹; 秦嘉政²; 任佳³; 杨星²; 杨玲英²; 蒋翠荣³; 袁曲⁴; 李丽红¹; 和玉权¹; (1.云南省地震局丽江地震台,云南丽江 674100; 2.云南省地震局,昆明 650224; 3.河北省地震局张家口中心台,河北张家口 075000; 4.湖北省地震局宜昌地震台,湖北宜昌 443000)

Author(s):: YANG Yue-wen¹; QIN Jia-zheng²; Ren Jia³; YANG Xing²; YANG Ling-ying²; (1.Lijiang Seismic Station,Earthquake Administration of Yunnan Province,Lijiang 674100,Yunnan,China)(2.Earthquake Administration of Yunnan Province,Kunming 650224,Yunnan,China)(3.Zhangjiakou Central Seismic Station,Earthquake Administration of Hebei Province,Zhangjiakou 075000,Hebei,China)(4.Yichang Seismic Station,Earthquake Administration of Hubei Province,Yichang 443000,Hubei,China)

Keywords:: water-tube tiltmeter; M9.0 Sumatra-Andaman earthquake; free oscillation of the Earth; spheroidal oscillation

摘要:: 利用云南省数字化水管仪的观测资料,采用功率谱密度估计方法,在没有对资料进行去固体潮处理的情况下,准确获得了2004年12月26日苏门答腊大地震激发的₀S₄～₀S₃₀基频球型自由振荡,并与前人的观测结果进行比较,同时对照了PREM模型的理论计算周期,发现水管仪观测与这三者符合得非常好,除₀S₄振型的观测周期和周期1、周期2、周期3的相对误差均大于0.3%外,其余的差别在3‰以下。研究表明,利用数字化水管仪观测资料的确可以提取到苏门答腊大地震激发的地球球型振荡,这就为地球自由振荡的研究提供了一种新的观测手段。

Abstract:: By power spectrum density estimation,we extract the fundamental-frequency,spheroidal,free oscillation(₀S₃～₀S₂₆)of the Earth excited by the M9.0 Sumatra-Andaman great earthquake on 26 December 2004 from the data of digital water-tube tiltmeters from Yunlong seismic station,Yongsheng seismic station,and Chuxiong seismic station in Yunnan Province without eliminating the Earth's tide.Comparing the extracted free oscillation with those observed by Benioff with the strainmeter Isabella and by Ness with the gravimeter Lacoste-Romberg and referring to the period of the extracted oscillation with that of the theoretical oscillation from the Preliminary Reference Earth Model(PREM),we find that they are in very good accordance with each other; the relative errors of ₀S₄ period,period 1,period 2,period 3 are greater than 0.3% while the relative errors of other periods are less than 3‰.This proves that extracting the free oscillation of the Earth from the data of digital water tube tiltmeter is a new approach.