Anisotropic attenuation of the macroseismic intensity

Aim of this study is to forecast the spatial distribution of the damages caused by an earthquake in the area surrounding its epicentre. The macroseismic intensity Is at a site is a direct measure of the local effects produced by an earthquake of epicentral intensity I0. Assuming that Is, as well as the decay ?I = I0 - Is, is a random variable, first the attenuation was modelled under the assumption that the decay is isotropic; then this model was extended to the anisotropic case when the generating fault is known. Since this information is not always available, we propose a way to obtain indications on the location of the fault through the spanning ellipse of the sites enclosed into the first isoseismal.