Earthquakes occur even in places where no deformation related to horizontal tectonic plate motion is expected.
Among the regions where no present-day horizontal deformation can be quantified to the level of accuracy of GPS measurements (i.e., 0.3 mm/yr), the Alps and the Pyrenees mountain ranges (Western Europe) or the New Madrid area (USA) can be cited.
In these areas, the causes for the recorded seismicity are puzzling to earth scientists. Here, P. Vernant and colleagues show that erosion of topography can lead to vertical motions, which in turn can create very low horizontal deformations and earthquakes.
This implies that seismic hazard assessment for low strain rate areas needs to be revisited, because erosion-related earthquakes could increase seismic hazard.
P. Vernant et al., DOI: 10.1130/G33942.1.