Two　end　members　of　the　Xinmocun　lacustrine　sediment　grain　size　in　the　upper　reaches　of　the　Minjiang　River　were　inverted　using　the　end　member　(EM)　model　of　sediment　grainsize.　The　provenance　of　sediments　and　activity　of　paleoearthquake　of　each　EM　were　discussed　based　on　the　frequency　of　the　EMs,　sedimentology　analysis,　geological　and　tectonic　background.　EM1　deposited　in　lacustrine　environments　during　a　seismic　period　and　represents　very　fine　particles　brought　by　wind　nearby;　EM2　deposited　in　lacustrine　environments　in　an　extremely　disastrous　condition　(e.　g.　earthquakes,　landslides　etc.　)　and　represents　the　dust　and　few　fluvial　deposits　from　nearby　sources.　Comparative　analysis　of　EM2　percentage,　mean　grain　size,　magnetic　susceptibility　and　geochemical　ratios　(e.　g.　SiO2/Al2O3,　TiO2/Al2O3,　CaO/Al2O3,　Sr/Al2O3,　Rb/Sr,　Na2O/Al2O3)　indicates　that　all　the　indexes　vary　greatly　with　grain　sizes　and　possibly　point　to　seismic　events.　A　total　of　twenty-six　possible　earthquake　events　have　been　identified.　Based　on　the　relation　of　the　cumulative　thickness　of　sand　sediments　with　magnitudes　of　earthquakes,　earthquake　magnitudes　representing　seismic　events　were　obtained　in　this　study:　sixteen　earthquakes　of　magnitude　5.0~6.0,　five　6.0~7.0　and　five　more　than　7.0.　Compared　to　the　traditional　method　of　sediment　grain　size　analysis,　the　EM　model　can　not　only　determine　the　EMs　and　percentage　of　each　component,　identify　the　sediment　provenance　and　dynamic　regional　sedimentary　environment,　but　also　recognize　the　tectonic　events　(earthquake,　etc.　)　of　sedimentary　record.　Therefore,　this　method　can　better　explain　the　role　of　tectonic　activity　in　geological　and　geomorphological　evolution.　©　2020,　Science　Press.　All　right　reserved.