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Ongoing Deformation and Earthquake Potential in Northwestern Colombia Due to the Slow Subduction of the Caribbean Plate Revealed by GPS Data

Session: Subduction Processes Along Latin America Subduction Zones II

Type: Oral

Date: 4/19/2021

Presentation Time: 03:00 PM Pacific

Description: 

Colombia is a region of complex tectonics due to the interaction between the Caribbean, Nazca and South American plates, as well as other major tectonic blocks. Under this setting, the GPS network has become an important tool to study the regional kinematics, understand the crustal deformation and infer its potential implications in terms of geohazards.

GPS velocity data for the period 2008-2017 indicate a differential motion of the northern part of the North Andean Block, which also presents a mechanical interaction with the subducting Caribbean plate. Additionally, this region presents significant compressive GPS strain rates (65 nanostrain/yr). Thus, we perform a 3D GPS data inversion to estimate the extent and degree of interplate locking along this boundary following Sagiya and Mora-Páez (2020).

Our results show a shallow and fully locked patch south of Cartagena city, as the first indication of a possible seismic/tsunami hazard in this region. Considering a perfectly elastic behavior of the overriding plate, the source region would be able to generate a M_w 8.2 earthquake every 700 years. This long recurrence interval is due to the slow convergence of the Caribbean plate (7 mm/yr). Another possibility is under the assumption of plastic deformation of the hanging wall of the subduction. However, discrepancy of one order of magnitude between long-term and geodetic strain rates do not support this interpretation.

Available evidence suggests that a careful attention is necessary for the first scenario due to its hazardous implications and the lack of a large earthquake in the last 500 years. Indeed, it has been reported that other slow subduction zones worldwide (e.g. Calabria and Gibraltar) are able to generate M8 earthquakes and tsunamis (Gutscher and Westbrook, 2009). Nevertheless, an integration of paleoseismological and paleotsunami records becomes urgent in order to identify recent crustal shortening or large past earthquakes/tsunamis in northwestern Colombia.

Presenting Author: Sindy C. Lizarazo

Student Presenter: Yes

Authors