A three-component geomagnetic survey was carried out during the period from 2002 to 2004 in China including Jiujiang-Ruichang region. Comparing the “2005.0 surface spline model of China geomagnetic field” created on the basis of the survey data with the “1970.0 surface spline model of China geomagnetic field”, we can see an obvious abnormity in the geomagnetic horizontal component within a range of about 100 km around the epicenter of the MS=5.7 Jiujiang-Ruichang earthquake occurred on November 26, 2005. After the earthquake, we carried out a repeated geomagnetic survey at 21 stations in the Jiujiang-Ruichang region and created a corresponding “2005.0 partially revised surface spline model of China geomagnetic field”. By comparing the above three models, analyz-ing the geomagnetic horizontal component at the profile in the Jiujiang-Ruichang region and quantitatively study-ing the geomagnetic data of every stations around the MS=5.7 earthquake, we have obtained the geomagnetic ab-normity associated with this earthquake. Then the geomagnetic abnormity and its relation with seismic activity are discussed in this paper.
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