In this study new tomographic models of Colombia were calculated. I used the seismicity recorded by
the Colombian seismic network during the period 2006-2009. In this time period, the improvement of
the seismic network yields more stable hypocentral results with respect to older data set and allows to
compute new 3D Vp and Vp/Vs models. The final dataset consists of 10813 P- and 8614 S-arrival
times associated to 1405 earthquakes. Tests with synthetic data and resolution analysis indicate that
velocity models are well constrained in central, western and southwestern Colombia to a depth of 160
km; the resolution is poor in the northern Colombia and close to Venezuela due to a lack of seismic
stations and seismicity.
The tomographic models and the relocated seismicity indicate the existence of E-SE subducting Nazca
lithosphere beneath central and southern Colombia. The North-South changes in Wadati-Benioff zone,
Vp & Vp/Vs pattern and volcanism, show that the downgoing plate is segmented by slab tears E-W
directed, suggesting the presence of three sectors. Earthquakes in the northernmost sector represent
most of the Colombian seimicity and concentrated on 100-170 km depth interval, beneath the Eastern
Cordillera. Here a massive dehydration is inferred, resulting from a delay in the eclogitization of a
thickened oceanic crust in a flat-subduction geometry. In this sector a cluster of intermediate-depth
seismicity (Bucaramanga Nest) is present beneath the elbow of the Eastern Cordillera, interpreted as
the result of massive and highly localized dehydration phenomenon caused by a hyper-hydrous oceanic
crust. The central and southern sectors, although different in Vp pattern show, conversely, a continuous,
steep and more homogeneous Wadati-Benioff zone with overlying volcanic areas. Here a "normalthickened"
oceanic crust is inferred, allowing for a gradual and continuous metamorphic reactions to
take place with depth, enabling the fluid migration towards the mantle wedge.
| Identifer | oai:union.ndltd.org:unibo.it/oai:amsdottorato.cib.unibo.it:4290 |
| Date | 28 March 2012 |
| Creators | Seccia, Danilo <1980> |
| Contributors | Chiarabba, Claudio |
| Publisher | Alma Mater Studiorum - Università di Bologna |
| Source Sets | Università di Bologna |
| Language | English |
| Detected Language | English |
| Type | Doctoral Thesis, PeerReviewed |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess |
Page generated in 0.0024 seconds