Abstract

SANCHEZ, JOHN J et al. SPATIAL MAPPING OF THE B-VALUE AT GALERAS VOLCANO, COLOMBIA, USING EARTHQUAKES RECORDED FROM 1995 TO 2002 . Earth Sci. Res. J. [online]. 2005, vol.9, n.1, pp.29-35. ISSN 1794-6190.

The catalog of volcano-tectonic earthquakes at Galeras volcano, Colombia , was analyzed to determine the magnitude of completeness of the seismograph network and to explore the subsurface structure by mapping the b-value of the frequency-magnitude distribution. By using 8,435 well-located earthquakes between 1989-2002 we found the catalog to be complete above MD=0.26. The average b-value of 0.71 was found to be the result of an unintentionally stretched magnitude scale. The two- and three-dimensional mapping of b-value illuminates a vertically elongated structure beneath the active crater of Galeras down to a depth of 6 km, which may be associated with a conduit, or alternatively, with a shallow region of temporary magma storage. A structure with this geometry and location has not been found before in previous studies of b-value on volcanoes around the world.

Keywords : seismology; Galeras volcano; b-value; earthquarques.

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