jgg     2007 27 (4):  105-111    ISSN: 0412-1961  CN: 21-1139/TG FURTHER DISCUSSION ON VIEW OF SEISMIC PRECURSOR FROM DOUBLE FORCE SOURCE Lu Mingyong China Center for Earthquake Disaster Emergency and SAR, Beijing 100049 Received: 1900-01-01  Revised: 1900-01-01  Online: null Supporting info null