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The hidden simplicity of subduction megathrust earthquakes

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Science  22 Sep 2017:
Vol. 357, Issue 6357, pp. 1277-1281
DOI: 10.1126/science.aan5643

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Universal scaling for big quakes

The amount of energy released as a large fault ruptures provides some clues about the overall size of an earthquake. Meier et al. looked at this energy release for more than 100 large earthquakes. Although the overall size of an earthquake cannot be predicted from the rate of energy release, a minimum size can be estimated. Estimating this minimum size could add valuable seconds to early earthquake warning algorithms, helping to avoid damage and save people from injury or death.

Science, this issue p. 1277

Abstract

The largest observed earthquakes occur on subduction interfaces and frequently cause widespread damage and loss of life. Understanding the rupture behavior of megathrust events is crucial for earthquake rupture physics, as well as for earthquake early-warning systems. However, the large variability in behavior between individual events seemingly defies a description with a simple unifying model. Here we use three source time function (STF) data sets for subduction zone earthquakes, with moment magnitude Mw ≥ 7, and show that such large ruptures share a typical universal behavior. The median STF is scalable between events with different sizes, grows linearly, and is nearly triangular. The deviations from the median behavior are multiplicative and Gaussian—that is, they are proportionally larger for larger events. Our observations suggest that earthquake magnitudes cannot be predicted from the characteristics of rupture onsets.

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