jgg     2013 33 (增2):  109-113    ISSN: 0412-1961  CN: 21-1139/TG MODEL ANALYSIS OF PASSIVE SINGLE STAGE SPRING VIBRATION  ISOLATION SYSTEM MODEL ANALYSIS 1）Key Laboratory of Earthquake Geodesy，Institute of Seismology，Wuhan 430071 2）Wuhan Base of Institute of Crustal Dynamics，CEA，Wuhan 430071 Received: 2012-10-23  Revised: null  Online: 2013-10-24 Supporting info