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Reply to “VAN earthquake predictions‒An attempt at statistical evaluation,” by Y.Y. Kagan
Author(s) -
Varotsos P.,
Lazaridou M.
Publication year - 1996
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/96gl00909
Subject(s) - aftershock , randomness , earthquake prediction , cutoff , induced seismicity , earthquake magnitude , magnitude (astronomy) , geology , simple (philosophy) , statistical physics , seismology , mathematics , statistics , physics , philosophy , geometry , quantum mechanics , astrophysics , epistemology , scaling
A number of successful VAN predictions were omitted in Kagan's [1996] calculations. Furthermore, Kagan assumed an arbitrary cutoff in the magnitude of the earthquakes. We show that, for the SI‐NOA catalog, the VAN high rate of success is not due to a retroactive adjustment of prediction rules, or to the non‐randomness of seismicity. If we remove dependent events from the catalog, the prediction effect still remains statistically significant when considering the prediction rules suggested by VAN since 1986, and not omitting a number of successful predictions referring to main shocks. The simple prediction algorithm, suggested by Kagan [1996], cannot be considered as giving similar results with VAN; this is so because, as we show with simple examples, the number of successes is not a safe criterion to compare two methods. Kagan's [1996] algorithm predicts almost exclusively aftershocks, while VAN predicts a comparable (or even larger) number of earthquakes most of which are main shocks. For the PDE(NOAA) catalog, a re‐analysis shows that the VAN predictions' rate of success cannot be attributed to chance.