Resumo

MONSALVE JARAMILLO, Hugo; CORREA MONTANO, Isabel Cristina  e  VALENCIA MINA, William. SEISMOLOGICAL OBSERVATORY AT QUINDIO UNIVERSITY (O.S.Q.): A FIRM LONG-TERM STEP TOWARD RESOLVING REGIONAL SEISMICITY . Earth Sci. Res. J. [online]. 2005, vol.9, n.2, pp.85-98. ISSN 1794-6190.

The Coffee Belt (the central coffee-growing zone in Colombia ), and more particularly, the state of Quindio is constantly hit by earthquakes of different magnitudes. Earthquakes result from the complex regional tectonics, brought about by interaction between the Nazca, Caribbean , and South American plates. The convergence of these plates is responsible for the formation of the Andes . For these reasons, the OSQ (Sesimological Observatory of Quindio, from its acronym in Spanish) and INGEOMINAS, as government offices in charge of monitoring earthquake activity, have to contribute, along with research centers of the region, to the development of seismological studies and analysis of local tectonic activity in order to obtain new knowledge regarding natural disasters which are threat to the communities in region and be able to better understand the internal crustal structure in the Coffee Belt region. The combination of different velocity models for the Coffee Belt region has allowed the definition of key elements to have better insight about the structure of the crust. Consequently, determining an improved new velocity model for the Colombian coffee-growing region has helped to a better location of earthquakes and to a more accurate determination of differences in crustal thickness and the structure of the upper mantle between adjacent terrains that were built during different geological periods. The ML magnitude was determined for the near and intermediate fields, and, using the model presented in this article, the problem of dynamic range saturation of seismographs during relevant earthquakes in near field is overcome. The local magnitude of some shallow earthquakes was calculated using shocks with epicentral distances ranging between 10km and 300km as well as the magnitudes of some deep earthquakes with hypocentral distances ranging between 100km and 600km.Seismic potential assessment in the Coffee Belt region begins with recent seismicity recorded in Chocó and the northern part of Valle (a state in Colombia) and is based on comparative analysis between this seismicity and the one recorded before the occurrence of the most important earthquakes in the last 42 years. Finally, taking into consideration the two subduction sources, an earthquake with seismic moment magnitude ranging between 6.7 and 7.3 could be expected within the next decade, having a probability of 87%.

Palavras-chave : Quindío; sismicity; instrumentation.

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