The 2025 Santorini earthquake sequence unveils the tail of the magnitude-frequency distribution

Abstract

We present a statistical analysis of the intense earthquake swarm near Santorini, Greece, in 2025. A change-point analysis of the b-value of the Gutenberg–Richter frequency-magnitude distribution indicates that, despite obvious spatiotemporal changes in seismicity characteristics during the crisis, there was no significant change of b with time. The high event rate provides a large statistical sample equivalent to a much longer catalog in terms of event numbers. This offers the chance to study the upper tail of the frequency-magnitude distribution in detail. While typical earthquake catalogs suffer from poor sampling in this domain, the Santorini crisis is suited for constraining the largest earthquakes. Assuming a truncated Gutenberg–Richter distribution and using well-established methods from frequentist statistics, like calculation of exact confidence intervals, we find that the maximum observed magnitude m=5.2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$m=5.2$$\end{document} is close to the estimated maximum possible magnitude. We conclude that with 95% confidence, no earthquake with magnitude m>5.35\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$m>5.35$$\end{document} can be expected.