- Chang Heon-Young
- 韓國宇宙科學會誌 = Journal of astronomy & space sciences
- 23, n.3
- pp.199-208
- 2006
- 원문 바로보기
The terrestrial impact cratering record recently has been examined in the time domain by Chang & Moon (2005). It was found that the <TEX>${\sim}26$</TEX> Myr periodicity in the impact cratering rate exists over the last <TEX>${\sim}250$</TEX> Myrs. Such a periodicity can be found regardless of the lower limit of the diameter up to D <TEX>${\sim}35km$</TEX>. It immediately called pros and cons. The aim of this paper is two-fold: (1) to test if reported periodicities can be obtained with an independent method, (2) to see, as attempted earlier, if the phase is modulated. To achieve these goals we employ the time/frequency analysis and for the first time apply this method to the terrestrial impact cratering records. We have confirmed that without exceptions noticeable peaks appear around <TEX>${\sim}25$</TEX> Myr, corresponding to a frequency of <TEX>${\sim}0.04(Myr)^{-1}$</TEX>. We also find periodicities in the data base including small impact craters, which are longer. Though the time/frequency analysis allows us to observe directly phase variations, we cannot find any indications of such changes. Instead, modes display slow variations of power in time. The time/frequency analysis shows a nonstationary behavior of the modes. The power can grow from just above the noise level and then decrease back to its initial level in a time of order of 10 Myrs.