| After the main shock,a certain number of aftershocks usually follow in a short period of time.Due to the randomness of parameters such as the magnitude,epicenter location,and depth of the aftershock,it still poses a great potential threat to the structure that has not been repaired or is intact.Since aftershocks are bred by the main shock,there is a certain correlation between aftershocks and main shocks in terms of magnitude and source fault.Therefore,in the aftershock risk analysis,how to properly consider the correlation and randomness of the main shock and aftershocks in various aspects has become the key.In view of the above reasons,this paper gives an aftershock risk analysis method considering the correlation of main aftershocks,which is as follows:Firstly,when the main shock information is known,according to the relationship between the main shock and the aftershock in terms of magnitude,source and fault trend,the Monte Carlo method is used to simulate the aftershock seismic information that may occur in the future.Then,combined with the definition of parameters such as fault moment and up-disk effect,all the parameters required for the ground motion prediction equation are calculated.On this basis,the conditional mean spectrum of aftershocks is used as the target response spectrum to calculate the seismic hazard curve of aftershocks under given main shock conditions.Secondly,the study area is delineated around the main earthquake epicenter,and the seismic risk curves of all the study sites were calculated.On this basis,with the definition of uniform hazard spectrum,the calculation method of uniform hazard spectrum of aftershocks after the main shock and the division method of aftershock influence field are studied.Finally,this paper sets the main shock to different magnitudes,and then uses the statistical relationship to give the fault information of the set aftershock.On this basis,with the help of the correlation between main shock and aftershock,the aftershock seismic risk curve,aftershock uniform risk spectrum and aftershock ground motion field analysis method of surrounding sites under the action of main shock are studied.Through this research,an aftershock risk analysis method that can fully consider the correlation between main shock and aftershock in magnitude,fault information and spectral parameters is given,and the influence field corresponding to the overtaking probability of large earthquake,medium earthquake and small earthquake at the research site is given.This method can reasonably reflect the correlation between main shock and aftershock,so as to improve the rationality of aftershock risk curve,uniform hazard spectrum and influence field division.The research in this paper shows that after a strong mainshock occurs,the seismic levels that can be caused by aftershocks in the surrounding area remain high,still posing a significant threat to structures that have not yet been repaired or even intact. |
