jgg     2013 33 (增2):  21-23    ISSN: 0412-1961  CN: 21-1139/TG OPERATION STATUS ANALYSIS OF EXTENSOMETER AT  CHANGSHU SEISMOSTATION Changshu Seismostation，Earthquake Administration of Jiangsu Province，Changshu 215500 Received: 2012-12-08  Revised: null  Online: 2013-10-24 Supporting info