A new method to estimate paleoseismic PGA using dynamic numerical back-analysis of keystone displacements in historic masonry structures

We present here a novel approach to assess paleo strong ground motions from dynamic back analysis of key block displacements in a Roman arch and collapse of columns in a Byzantine church using the numerical discontinuous deformation analysis method. The obtained threshold values for paleo peak horizontal ground acceleration are utilized as an independent validity check for H-PGA predictions recommended by the local seismic building codes. Preliminary results from two different sites provide a good agreement between the H-PGA estimates arrived at by the two independent approaches.