The Triggering Mechanism for the largest Aftershock （ Ms = 6.3 ） of the Great Luhuo Event （ Ms =7.6） in 1973

INTRODUCTIONInrecentyears,thestudiesontemporaryandspatialfeaturesofaftershocksaroundepicentersandtheirmechanismhavebeenanimportantpartofseismology .Theaftershocksrelatedtothestateoffaultruptureofmainshockscouldbedistinguishedasthreetypes,theyare:(1)theaftershocksalongbro kenfaultsegments;(2 )theaftershocksontheborderoftherupturebelt;and (3)theaftershocksin ducedbymainshocksthatoccurredbeyondthemainruptures.Themechanismofthefirsttypemightbetheadjustmentoftheremnantasperityinthefaultplaneofm…

The Triggering Mechanism for the Largest Aftershock (Ms=6.3) of the Great Luhuo Event (Ms=7.6) in 1973

The Great Luhno Event ( Ms= 7.6) occurred on February 6, 1973 in Sichuan Province. There were a lot of aftershocks in the source area. The largest aftershock (Ms= 6.3) occurred along a normal fault zone between the Xianshuihe Fault and the Gnnzi-Yushu fault. Based on the focal mechanism solution, surface rupture, coseismic dislocation and seismo-geological tectonics of the event, an elastic dislocation model of the Great Luhuo Event with a strike slip mechanism was designed and the Coulomb Failure Stress Change (ΔCFS) in the slip direction on normal faults along and surrounding the source zone due to the event was calculated. The results showed that the largest aftershock occurred in an area with ΔCFS＞O, and that ΔCFS=4.5MPa. Therefore, the largest aftershock was probably triggered by the Coulomb Failure Stress Change.