THE 20 MARCH 2006 EARTHQUAKE OF LAALAM (KABYLIA, ALGERIA) (Mw=5): GEOLOGICAL AND GEOPHYSICAL PROSPECTIONS (AMBIENT VIBRATION NOISE) AND CORRELATIONS WITH DAMAGES. LE SÉISME (Mw = 5) DE LAALAM (KABYLIE, ALGÉRIE) DU 20 MARS 2006 : PROSPECTIONS GÉOLOGIQUES ET GÉOPHYSIQUES (BRUIT VIBRATOIRE AMBIANT) ET CORRÉLATIONS AVEC LES DOMMAGES
Abstract
Geological and geophysical (ambient vibrations) prospections conducted after the moderate Laalam earthquake (Mw = 5, USGS), demonstrate that structure destructions following this event are not related to site effects. Nevertheless, damages and human losses (4 dead, 68 injured) may be explained by vulnerable habitations and the epicenter proximity, either directly (ground shaking) or indirectly, by induced effects. Induced effects are constituted of soil and road cracks, rock falls, and a landslide reactivated by the earthquake. However, the surficial cracks are not expressing the fault on the surface, because of the moderate magnitude of the event. This study is comforting the need of moderate earthquake induced effects and raises the important problem of damages caused by low to moderate earthquakes in Algeria and buried fault location and mapping.