Analysis of macroseismic and instrumental data for the study of the 19 November 1923 earthquake in the Aran Valley (Central Pyrenees)

The 19 November 1923 earthquake in the Aran Valley (Central Pyrenees), with observed maximum intensityI _max = VIII (MSK), has been studied through the compiling and reviewing of macroseismic information and collecting and processing early seismograms. Analysis of macroseismic data gives a focal depth ofh = 5 km and an anelastic attenuation coefficient 10^–3 km^–1. Analysis of early instrumental records allows the computation of estimate of magnitude (M _L = 5.6) and seismic moment (M _o = 1.1 × 10¹⁷ N × m) which are consistent with the values ofI _o andh obtained from macroseismic data.