Jumping Earthquakes: limits to rupture forecasting exposed by instantaneously triggered earthquake doublet

An important question in understanding the potential magnitude of earthquakes, and consequently the hazard certain faults may pose, is the distance over which earthquakes can jump during rupture. This is because a critical observation of earthquake scaling which holds true is that the longer a fault rupture, the larger the earthquake. In a bigger earthquake, the ground shaking is more severe, it occurs over a wider area and lasts longer; exposing more buildings and people to a greater level of hazard.

The previous consensus on the control of the maximum likely leap in an earthquake was that an offset between faults of 5 km would probably be enough to stop a rupture – the gap being too much of a physical barrier for the earthquake to jump across. This limit of 5 km is used in some standard seismic hazard assessments.

However, an international team of researchers, have forensically unpicked from a seismic event that struck Pakistan in 1997, a pair of large earthquakes that had been previously catalogued as one. In a study published in Nature Geoscience, they combine satellite observations with seismology, to show that this pair of earthquakes involved a massive jump of 50 km between fault segments during the rupture – this is 10 times larger than the current accepted rule that is used in assessing earthquake hazard.

Research Paper: Nissen, E. K., Elliott, J. R., R. A. Sloan, T. J. Craig, G. J. Funning, A. Hutko, B. E. Parsons & T. J. Wright (2016) Dynamic triggering of an earthquake doublet exposes limitations to rupture forecasting, Nature Geoscience, doi:10.1038/NGEO2653

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