Mapping of b-values, earthquake relocation, and Coulomb stress changes during 1992–2007 in the Murindó seismic zone, Colombia

摘要

Seismicity in the Murindó seismic zone, Colombia (6° to 8° and − 75.5° to − 78.0°) during 1992–2007 included the occurrence of the M _W 6.6 foreshock on October 17, and M _W 7.1 mainshock on October 18, 1992, and aftershocks, which caused severe damage throughout the region. We modeled this seismic sequence by means of Coulomb stress changes imparted by slip along two semi-vertical fault planes with left-lateral motion and subdivided slip. Seismicity thereafter (1993–2007) was characterized by earthquakes magnitude in the range 0.7−6.1 for which a magnitude of completeness M _C = 2.7 was determined. b-values are relatively high to the south of the study region and relatively low to the north and northwest. The relocation of epicenters indicates that recent seismicity may be occurring on a fault that is yet to be mapped under the Atrato river valley. We conclude that the 1992 seismic sequence was a case of a major earthquake facilitated by the stress changes imparted during a strong rupture the previous day and that the aftershocks and background seismicity in the region can be explained by static Coulomb stress changes up to 50.1 bar. Our results have implications for hazard in Colombia and serve as basis to foster future investigations.