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SINGER, ANDRE, CARLOS BELTRAN, and MIGUEL LUGO, Venezuelan Foundation for Seismological Research (FUNVISIS), Caracas, Venezuela

ABSTRACT: Active Faulting in the Southwestern Venezuelan Andes and Colombia Borderland

In the southern Andes, the Bocono fault shows a progressive disactivation of its right lateral movement, resulting from its attenuation against the transversal system of Bramon and its kinematic connection to the "Pamplona indenter," considered as a part of the plate boundary between the Caribbean and South America. Near the Colombian frontier, the velocity of Bocono fault is probably less than 1 mm/yr. Such a decrease is explained because an increasing amount of the 1 cm/yr slip movement of the northern part of the fault is absorbed through a complex branching of the active trace, southwest Merida.

Another significative amount of the rate movement of Bocono fault, considered as plate boundary, results absorbed by subparallel active faulting systems located to the east (Uribante and Caparo Systems) and to the west sides (San Simon-Seboruco, and San Pedro-Aguas Calientes-La Don Juana systems). The last system, extending beyond the frontier, shows a particular seimotectonic importance, as a probable source of the 1875 Cucata earthquake.

In this way, the weight of the southwestern end of Bocono fault as a seismic source loses importance respect to the northern

segment located between la Grita and Merida where the 1610 and 1894 earthquakes occurred, and also as compared to the faults that define the "Pamplona indenter" like probable source for several other destructive earthquakes.

AAPG Search and Discovery Article #90988©1993 AAPG/SVG International Congress and Exhibition, Caracas, Venezuela, March 14-17, 1993.