Abstract

KINGLAND, Jorge; TORRES, Rafael A  and  INGLESSIS, Pether. Attenuation equation of macrosismic intensity and isoseismals map for the 1894 great earthquake of andes.. IMME [online]. 2008, vol.46, n.1, pp.01-22. ISSN 0376-723X.

This work evaluates of historical information about the April 28^th 1894 earthquake, which is better known as “The Great Earthquake of Venezuelan Andes”, assigning macro-seismic intensities to different Venezuelan cities and borderline areas, where it was reported to be felt. The Modified Mercalli Intensity Scale (MMI) was used to get an equation or a local attenuation pattern of the macro-seismic intensity to this specific earthquake, using a statistical regression method. The intensities were taken without making any distinction if the damage were originated due the vibration located on the soil, soil liquefaction or any other local phenomenon. Using the assigned intensities of each area, isoseismals curves were plotted, allowing us to have a graphic vision of the earthquake’s effects and its attenuation as a function of the distance. As a result, a preliminary equation is suggested, which let it calculate the intensities (I_i) in the region where the 1894 Great Earthquake of Los Andes (study area) hit, establishing a statistical validation of the equation that is mentioned before: I_i  = 10,7915 - 0,9963  ln (x_i - 5,942) - 0,00266 (x_i - 5,942); x_i ≥ 8,89 km The suggested equation shows the attenuation in the region as a function of the epicentral distance (x_i).

Keywords : Historic seismicity; seismic hazard; macro-seismic intensity; isoseismals; attenuation; attenuation law; statistical regression method.