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AGU: Journal of Geophysical Research, Solid Earth

 

Keywords

  • Costa Rica
  • Earthquake cycle
  • GPS
  • Interseismic megathrust coupling
  • Nicoya
  • Subduction zone

Index Terms

  • 1209 - Tectonic deformation
  • 1242 - Seismic cycle related deformations
  • 1243 - Space geodetic surveys

Paper in Press

JOURNAL OF GEOPHYSICAL RESEARCH, doi:10.1029/2012JB009230

Active Deformation near the Nicoya Peninsula, Northwestern Costa Rica, Between 1996 and 2010: Interseismic Megathrust Coupling

Key Points
  • Unprecedented imaging of interseismic megathrust coupling near Nicoya
  • Useful for earthquake hazard assessment and comparison with SSE, NVT, and LFEs
  • Global understanding of coupling behavior in shallow subduction environments

Authors:

Lujia Feng

Andrew V Newman

Marino Protti

Victor González

Yan Jiang

Timothy H Dixon

We use campaign and continuous GPS measurements at 49 sites between 1996 and 2010 to describe the long-term active deformation in and near the Nicoya Peninsula, northwestern Costa Rica. The observed deformation reveals partial partitioning of the Cocos-Caribbean oblique convergence into trench-parallel forearc sliver motion and less oblique thrusting on the subduction interface. The northern Costa Rican forearc translates northwestward as a whole ridge block at 11{plus minus}1 mm/yr relative to the stable Caribbean. The transition from the forearc to the stable Caribbean occurs in a narrow deforming zone of ~16 km wide. Subduction thrust earthquakes take 2/3 of the trench-parallel component of the plate convergence; however, surface deformation caused by interseismic megathrust coupling is primarily trench-normal. Two fully coupled patches, one located offshore Nicoya centered at ~15 km depth and the other located inland centered at ~24 km depth, are identified in Nicoya with the potential to generate an Mw 7.8 1950-type earthquake. Another fully coupled patch SE of Nicoya coincides with the rupture region of the 1990 Nicoya Gulf earthquake. Interface microearthquakes, non-volcanic tremor, low-frequency earthquakes, and transient slow-slip events generally occur in the intermediately to weakly coupled regions.

Received 12 February 2012; accepted 14 May 2012.

Citation: Feng, L., A. V. Newman, M. Protti, V. González, Y. Jiang, and T. H. Dixon (2012), Active Deformation near the Nicoya Peninsula, Northwestern Costa Rica, Between 1996 and 2010: Interseismic Megathrust Coupling, J. Geophys. Res., doi:10.1029/2012JB009230, in press.