Viscoelastic earthquake cycle model for the Caribbean subduction zone in northwestern Colombia: Implications of coastal subsidence for seismic/tsunami hazards

• Published in: Journal of South American earth sciences 2024-08, Vol.141, p.104931, Article 104931
• Main Authors: Lizarazo, Sindy Carolina, Sagiya, Takeshi, Mora-Páez, Héctor
• Format: Article
• Language: English
• Subjects: Caribbean northwestern Colombia; Elastic thickness; GPS data; Seismic/tsunami potential; Slow and flat subduction; Subsidence; Viscoelastic earthquake cycle model
• ISSN: 0895-9811; 1873-0647
• DOI: 10.1016/j.jsames.2024.104931

Recent interplate coupling results from the inversion of GPS data in northwestern Colombia have shed light on the seismogenic and tsunami potential along the Caribbean coast. The identified locked region on the subduction interface could generate an Mw8.0 earthquake every 600 years, followed by a tsunami. While observed horizontal velocities have been reproduced successfully by the elastic coupling model, vertical velocities remain unexplained and differ, both in their signs and magnitudes, from the model prediction. To explain 3-dimensional velocities, particularly rapid coastal subsidence, we evaluate the viscoelastic response of the lithosphere-asthenosphere system to an earthquake cycle at the Caribbean subduction zone. We confirm that the role of viscous relaxation on interseismic deformation is critical when the recurrence interval is longer than the asthenosphere relaxation time. Moreover, fitting observed crustal motions requires a strong lithosphere (60–100 km) consistent with the depth of the lithosphere-asthenosphere boundary. Our results support the hypothesis of the Caribbean as a locus of seismic and tsunami hazards but do not resolve the vertical motion paradox at different time scales since the interseismic crustal motions recover completely the coseismic and postseismic displacements caused by the potential mainshock. Supplementary geological investigation is essential to validate our current interpretation and resolve the remaining gaps. •Possibility of an Mw8 earthquake in the Caribbean of Colombia validated by a viscoelastic earthquake cycle model.•The viscoelastic response of the Earth-system is crucial for geodetic data interpretation.•Large co- and inter-seismic vertical motions are independent of the subduction rate and the geometry of the subduction zone.•No marine terrace creation due to earthquake activity as co- and post-seismic motions are recovered in one earthquake cycle.•A strong “thick” lithosphere is required to support tectonic stresses over long earthquake cycles.