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Possible seasonality in large deep-focus earthquakes

TitlePossible seasonality in large deep-focus earthquakes
Publication TypeJournal Article
Year of Publication2015
AuthorsZhan Z.W, Shearer PM
JournalGeophysical Research Letters
Date Published2015/09
Type of ArticleArticle
ISBN Number0094-8276
Accession NumberWOS:000363412400017
Keywordscatalog; deep earthquake; earthquake statistics; seasonality; seismicity; subducting lithosphere; temperature

Large deep-focus earthquakes (magnitude>7.0, depth>500km) have exhibited strong seasonality in their occurrence times since the beginning of global earthquake catalogs. Of 60 such events from 1900 to the present, 42 have occurred in the middle half of each year. The seasonality appears strongest in the northwest Pacific subduction zones and weakest in the Tonga region. Taken at face value, the surplus of northern hemisphere summer events is statistically significant, but due to the ex post facto hypothesis testing, the absence of seasonality in smaller deep earthquakes, and the lack of a known physical triggering mechanism, we cannot rule out that the observed seasonality is just random chance. However, we can make a testable prediction of seasonality in future large deep-focus earthquakes, which, given likely earthquake occurrence rates, should be verified or falsified within a few decades. If confirmed, deep earthquake seasonality would challenge our current understanding of deep earthquakes.

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