Although small earthquakes are expected to produce weak shaking, ground motion is highly variable and there are outlier earthquakes that generate more shaking than expected-sometimes significantly more. We explore datasets of M 0.5-8.3 earthquakes to determine the relative impact of frequent, smaller-magnitude earthquakes that rarely produce strong ground motion, to rare, large earthquakes that always cause strong shaking. We find that the natural variability of ground motion, combined with the Gutenberg-Richter magnitude-frequency relationship, ensures that most occurrences of any ground motion come from earthquakes of smaller magnitude than expected, often > 2 magnitude units smaller. This holds even for very strong shaking (> 20%g), suggesting that M < 7 earthquakes could be a significant source of damage.
CITATION STYLE
Minson, S. E., Baltay, A. S., Cochran, E. S., McBride, S. K., & Milner, K. R. (2020). Shaking is almost always a surprise: The earthquakes that produce significant ground motion. Seismological Research Letters, 92(1), 460–468. https://doi.org/10.1785/0220200165
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