Group velocity in western Colombia from seismic noise and small earthquakes

Velocidad de grupo en el occidente de Colombia a partir del ruido sísmico y de pequeños sismos

Francisco J. Chávez-García1,*, Hugo Monsalve Jaramillo2,(†), Jose J. Vila Ortega1,2 

1 Universidad Nacional Autónoma de México, Instituto de Ingeniería, Coordinación de Ingeniería Sismológica. Circuito Escolar S/N, Ciudad Universitaria, Coyoacán, 04510, Ciudad de México.

2  Grupo Quimbaya, Universidad del Quindío. Carrera 15 #12N, Armenia, Quindío, Colombia.

*Autor para correspondencia: (F. J. Chávez-García) This email address is being protected from spambots. You need JavaScript enabled to view it.

† Lamentablemente, nuestro amigo y colega Hugo Monsalve falleció en abril pasado. Este será el último trabajo publicado por una persona muy entusiasta que ponía la investigación por arriba de todo. Descanse en paz.

How to cite this article: How to cite this article: Chávez-García, F. J., Monsalve Jaramillo, H., & Vila Ortega, J. J. (2026). Group velocity in western Colombia from seismic noise and small earthquakes. Boletín de la Sociedad Geológica Mexicana, 78(2), A301025. https://doi.org/10.18268/BSGM2026v78n2A301025

Manuscrito recibido: August 8, 2025. Manuscrito corregido: October 10, 2025. Manuscrito aceptado: October 24, 2025.

ABSTRACT

Seismic noise and earthquake records were used to determine group velocity distribution in the region. The analysis was restricted to vertical components to avoid ambiguity in identifying Rayleigh waves. 47 small earthquake records were processed using the multiple filter technique. We also used six months of continuous records of seismic noise in 12 broad band stations from Servicio Geológico Colombiano to estimate Green’s functions from seismic interferometry (long-term average of cross-correlation between station pairs). In this analysis we have shown that a non-linear stack of individual cross-correlation windows allows improving signal-to-noise ratios in those Green’s functions. These results were also processed with the multiple filter technique to estimate group velocities. In total, 111 group velocity dispersion curves were computed, which is not enough to compute a seismic tomography in the region of study, especially considering its size and the complexity of its geology. In addition, the period range for which results were obtained using small earthquakes is significantly different from that using seismic noise. However, we are able to estimate a reliable average group velocity of the region and show the variability of group velocities due to its complex geology.

Keywords: multiple-filer technique, small earthquakes, seismic noise, group velocity, Rayleigh waves, seismic interferometry.