利用湖州台数字伸缩仪观测资料的线应变转换成体应变资料,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
By using digital observations of extensometer to volume-strain-meter at Huzhou station and with power spectrum density estimationg method,acquire 0S4~ 0S30 fundamental sphere free oscillations caused by Japan earthquake on 11th Mar,2011 were obtained,without deleting influence of the earth tide on the data,then we compared it with with PREM model, we find that they are in very good accordance with each other ,this proves that extracting the free oscillation of the Earth from the data of digital extensometer to volume-strain-meter is a new approach.