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In Korea, the occurrence frequency of earthquakes has recently increased compared to the past. In neighboring countries such as Japan and China, damage from major earthquakes has also increased leading to high earthquake risk. This study quantitatively estimated the occurrence probability and frequency of huge earthquake using statistical frequency analysis on instrumental earthquake data at East sea in order to cope with earthquake damage. After adapting Various distribution functions such as Gumbel, Lognormal, Gamma, and Weibull for earthquake data, we applied mixed distributions to reflect the characteristics of the occurrence of earthquakes. The results show that the mixed models estimated earthquake magnitude larger than the Gutenberg-Richter (G-R) equation, and the mixed Gumbel distribution estimated most closed values with the G-R equation. It was found that the G-R equation is very limited to estimate a huge earthquake since there is no observed data over magnitude 8.0 and the frequency analysis is also limited to be applied in practice because the lack of data induces high uncertainty on the estimates of 1,000 year-earthquake. However, this study has an experiential significance in that the statistical frequency analysis was applied to instrumental earthquake data at East sea as an alternative.

Varicella-zoster virus (VZV) is a causative agent for chickenpox in primary infection and shingles after reactivation from latency. Both varicella and zoster can be prevented by live attenuated vaccines, but the molecular mechanism of attenuation is not clearly understood. In this study, the genome sequences of three varicella vaccine strains were analyzed for the genetic diversity including single nucleotide polymorphism (SNP) and genetic polymorphism. A total of 38 SNPs were identified including 29 substitutions and 9 insertion/deletions. The number of genetically polymorphic sites (GPS) was highest in Varivax and lowest in Varilrix. GPS in the R region including R1, R2, and R3 appeared to be responsible for the genetic polymorphisms in the open reading frame (ORF) 11, 14, and 22 in all three vaccine strains. A relatively large number of GPS were observed in ORF31, 55, and 62, which are known to be essential for virus replication, suggesting that the attenuation of the vaccine strains may be attributed by the diversity of these genes.