5:15 PM - 6:30 PM
[SSS30-P01] Operation of the SWIFT CMT analysis system in Colombia and characteristic of seismicity in the complex subduction zones
Keywords:SWIFT, Colombia, seismicity
The JST/JICA SATREPS project of "Research and development of disaster mitigation techniques of earthquake, tsunami, and volcano in Colombia" was started in 2015. We installed the SWIFT system (Nakano et al., 2008) in the Colombia Geological Survey and determined CMT solutions and source time functions of the Colombian regional earthquakes. We now carry out the following studies: 1) detection of very low frequency (VLF) earthquakes and tremors in Colombia, 2) determination of CMT solutions including small events which are not listed in the global CMT catalog. Although we have not been able to detect any VLF events until now, we obtained CMT solutions including small events by the SWIFT. The smallest magnitudes are Mw4.3 for shallow events and Mw4.6 for intermediate depth events. The global CMT catalog shows that the focal mechanisms in the Bucaramanga nest are highly variable, but our many CMT solutions show the mostly strike-slip faulting with some dip-slip components and SW-NE directions of P axis. Other events show focal mechanisms opposite to these mechanisms. Prieto et al. (2012) found repeating and "anti-repeating" earthquakes in the nest and suggested that the nest is not a volumetric but a planar seismic activity. Our results also support their idea, but we need more information of further past events. Toward understanding the nature of the nest and the complex subduction processes, we will also analyze the focal mechanisms of smaller events using P wave polarities.