SeveralearthquakeswithMs≥5.0occurredintheDatongseismicregionin1989,1991and1999,TheprecisefocuslocationoftheearthquakesequencewasmadebytherecordsoftheremotesensingseismicstationnetworkinDatong.Usingthatdatatogetherwithmacro-intensitydistributionandfocalmechanismsolutions,weanalyzethedifferenceamongthreesubsequences.Theresultsshowthatthefocalfaultofthe1999Ms5.6earthquakewasaNWW-trendingleft-lateralstrike-slipfault.Itis16kmlongand12kmwide.Itdevelopedatthedepthof5kmandisnearlyverticalindip.Thetwopreviousearthquakesubsequences,however,weregeneratedbyactivityalongNNE-trendingright-lateralstrike-slipfault.Itcanbefoundthattherupturedirectioinofthe1999earthquakehaschanged.Itisgenerallyfoundthatarupturezonehasmorethantwodirectionsandhasdifferentstrengthalongthesetwodirections.Thecomplicatedegreeoffocalcircumstanceisrelatedtothetypeofearthquakesequences.ThereistheNE-trendingDawangcunfaultandtheNW-trendingTuanbufaultintheseismicregion,butnoproofindicatesaconnectionbetweenfocalfaultsandthesetwotectonicfaults.Thefeaturethatfocalfaultsofthreesubsequencesarestrike-slipisdifferentfromthatofthetwotectonicfaults.Itissuggestedthatthe1999earthquakesubsequencewaspossiblygeneratedbyanewrupture.
