Gravitational potential energy and active deformation in the Apennines

- We investigate role of gravitational potential energy (GPE) in narrow mountain belts.
- The simple geometry leads to a direct relationship between crustal velocities and GPE.
- 141 CGPS observations across the Apennines agree within error with this relationship.
- Deformation is explained by internal GPE variations; external forces are not required.
- Dynamical models of deformation may be useful for assessment of seismic hazard.

We use velocity measurements from a network of continuous GPS sites spanning the Apennines of peninsular Italy to test the hypothesis that the active deformation of the region is explained by variations in gravitational potential energy of the lithosphere. The simple geometry of the mountain chain allows us to treat the deformation as two-dimensional, neglecting gradients of velocity along the strike of the chain. Under this assumption, the integral of gravitational potential energy per unit area of the lithosphere (GPE) in the direction perpendicular to the chain is related by a simple expression to the velocity in the same direction. We show that the observed velocities match this expression with an RMS misfit of 0.5mm/yr. This agreement suggests that deformation of the Apennines reflects a balance, within the mountain chain itself, between lateral variations in GPE and the stresses required to deform the lithosphere. Forces arising from processes external to the belt are not required to explain the observations.