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 intensity I-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 of h = 5 km and an anelastic attenuation coefficient alpha less than or equal to 10(-3) km(-1). Analysis of early instrumental records allows the computation of estimate of magnitude (ML = 5.6) and seismic moment (M(o) = 1.1 x 10(17) N x m) which are consistent with the values of I-o and h obtained from macroseismic data.