Variations in plate interface reflectivity within the rupture zone of the 2014 Iquique earthquake sequence: evidence from seismic and bathymetric data
Abstract
The 2014 Iquique earthquake sequence offshore northern Chile ruptured the marine forearc between 19.5°S-21°S. A grid of seismic reflection and refraction profiles was acquired to document the geologic structure of the upper and lower plates and the rheological properties of the boundary zone between them during cruise MGL1610 under the framework of the PICTURES (Pisagua-Iquique Crustal Tomography to Understand the Earthquake Source) project. Utilizing multiple suppression techniques and ray-based tomographic inversion, we have achieved enhanced pre-stack depth migrated images to a depth of 40 km. Line MC25, located in the southern part of the 2014 rupture area, displays a pronounced plate boundary reflection that can be tracked to a depth of ~16 km. In contrast, on line MC04, located north of the 2014 rupture area, the plate boundary reflection is clearly visible to ~40 km depth and reveals topography on the plate boundary. We consider several explanations for this contrast in plate boundary reflectivity. (1) The rupture process may have decreased plate boundary reflectivity by, for example, releasing fluid trapped in this zone. (2) An along-strike change in the orientation of the inherited spreading fabric in the subducted plate may affect the amount of fluid-rich sediment that is subducted with the oceanic crust, resulting in a stronger plate boundary reflection on MC04, where the subducting plate fabric is perpendicular to the deformation front. (3) Differences in background noise levels resulting from environmental or near-surface geology affect the detection threshold for low-amplitude plate boundary reflections.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMT053.0014M
- Keywords:
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- 1242 Seismic cycle related deformations;
- GEODESY AND GRAVITY;
- 3613 Subduction zone processes;
- MINERALOGY AND PETROLOGY;
- 7240 Subduction zones;
- SEISMOLOGY;
- 8170 Subduction zone processes;
- TECTONOPHYSICS