1,2,- 1Universitat de Barcelona, Facultat de Ciències de la Terra, Departament de Dinàmica de la Terra i de l'Oceà, Barcelona, Spain (Alvaro.Gonzalez@ub.edu)
- 2Centre de Recerca Matemàtica, Bellaterra (Barcelona), Spain
- 3Department of Physics, Universitat Autònoma de Barcelona, Bellaterra (Barcelona), Spain
- 4Department of Mathematics, Universitat Autònoma de Barcelona, Bellaterra (Barcelona), Spain
Beno Gutenberg and Charles F. Richter (1941) already hypothesized that their exponential relation between the magnitude and occurrence frequency of earthquakes would not be valid for the largest ones, as there should be a maximum limit to the earthquake size. This departure would have profound implications for global seismic hazard assessment, as there would actually be fewer large earthquakes than extrapolated from the distribution of smaller ones.
But statistically proving or disproving this hypothesis has been elusive, and a debate is ongoing on whether a statistically significant departure can be observed in the available global data. It was first necessary to develop a magnitude scale reliable up to the largest earthquake sizes (moment magnitude Mw, in the 1970s) and gathering ever-increasing earthquake catalogues (especially since the 1980s).
Not all statistical tests may identify a given departure as significant, because the largest earthquakes are infrequent, so their sample size is small. Recently it has been proposed that the whole observed distribution is still a simple exponential (Taroni, 2025). But several earlier results already had already identified a significant departure by which the tail of the distribution decays faster (Yoder et al., 2012, Serra & Corral, 2017, Corral & González, 2019).
To settle this question, here we use the largest available dataset: the ISC-GEM catalogue (International Seismological Centre, 2026) since the early XX century. In the analysis, we explicitly account for the magnitude uncertainties (substantial before the advent of the World-Wide Standardized Seismograph Network in the late 1960s).
This approach allows us considering the largest earthquakes ever instrumentally recorded and about triples the number of large earthquakes (Mw ≥ 6.5) available for analysis, compared to considering only the seismicity since the 1980s as typically done.
Using robust statistical tests, we show that the observed departure from a single Gutenberg-Richter law (clearly visible for Mw larger than ~7.6) is statistically significant, and examine the shape of this tail and its persistence in time.
References cited
Corral, Á., González, Á. (2019). Power law size distributions in geoscience revisited. Earth and Space Science, 6, 673–697. https://doi.org/10.1029/2018ea000479
Gutenberg, B. & Richter, C. F. (1941). Seismicity of the Earth. Geological Society of America Special Papers, number 34. 131 p.
International Seismological Centre (2026). ISC-GEM Earthquake Catalogue, https://doi.org/10.31905/d808b825
Serra, I., & Corral, A. (2017). Deviation from power law of the global seismic moment distribution. Scientific Reports, 7, 40045. https://doi.org/10.1038/srep40045
Taroni, M. (2025). The Gutenberg–Richter law strikes back: the exponentiality of magnitudes is confirmed by worldwide seismicity. Geophysical Journal International, 243 (2), ggaf366, https://doi.org/10.1093/gji/ggaf366
Yoder, M. R., Holliday, J. R., Turcotte, D. L., & Rundle, J. B. (2012). A geometric frequency-magnitude scaling transition: Measuring b = 1.5 for large earthquakes. Tectonophysics, 532-535, 167–174. https://doi.org/10.1016/j.tecto.2012.01.034
How to cite: González, Á., Corral, Á., and Serra, I.: The largest earthquakes recorded for over a century significantly depart from a simple Gutenberg-Richter distribution, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11541, https://doi.org/10.5194/egusphere-egu26-11541, 2026.
