Abstract

RENGIFO, Martín; LAFFAILLE, Jaime  and  CHOY, José. The earthquake of 12/21/2001 in the Mérida Andes. Rev. Fac. Ing. UCV [online]. 2010, vol.25, n.1, pp.5-17. ISSN 0798-4065.

On December 21, 2001, at nearly five o´clock in the afternoon, a strong earthquake shook a large extent of the Venezuelan Andes. This event was reported by the Laboratorio de Geofísica (Universidad de Los Andes) with magnitude Mb = 5,7; epicentral coordinates at 8.23º N - 70.96º W (northeast of Aricagua, Mérida state) and 6 km depth. The focal mechanism was determined using 33 P-wave first motion polarities. The solution is given by: (a) strike = 228º, dip = 75º and slip = 137º; (b) strike = 328º, dip = 48º and slip = 137º. The distribution of aftershocks shows that (a) is the fault plane, indicating a right lateral strike slip faulting. Due to the location of its epicenter, its type of faulting and the distribution of its aftershocks, it is considered that this event broke the Caparo fault, Venezuela. Another set of events occurred on the 26th of the same month, at approximately 20 km to the southwest. They also were associated with the Caparo fault, and produced a set of polarities consistent with the focal mechanism of the main event of December the 21th. Initially, no serious damages were reported, but a few weeks later it was known that they occurred in the El Quinó, a village of difficult access for its geographical location. The collected macroseismic information was enough to make an isosistic map, whose curves show some elongation with a NE-SW trend. Determination of earthquake parameters from this map point out the feasibility of the application, with good results, of the Shebalin seismic-field equations to historical earthquakes occurring in the Venezuelan Andes

Keywords : Earthquake; Intensity; Vulnerability; Caparo fault; Seismicity.