Unhinging an indenter: A new tectonic model for the internal deformation of Panama

New paleoseismic results from Panama, conducted as part of the seismic hazard assessment for the expansion of the Panama Canal, have led to a reevaluation of the tectonic framework and geologic history of the isthmus of Central America. We propose a soft block indenter model wherein the collision of Central America and South America has resulted in significant internal deformation of the isthmus. Deformation is accommodated by both rapid slip on conjugate strike-slip faults within the isthmus, as well as the generally assumed flexure and northward buckling of Panama. The model is kinematically self-consistent in that there are little or no space problems created with 3 Ma of retrodeformation. Sparse GPS velocity data are consistent to within uncertainties with the new geologically constrained block model, supporting the rapid and extensive internal deformation of Panama. Together, the paleoseismologic and geodetic data suggest that central Panama is an area of high risk due to earthquakes, which is consistent with the historical occurrence of several moderate to large earthquakes in this region. However, this is generally counter to the current perception in central Panama where most people live and where there have been no large, damaging earthquakes for over 100 years.