Seismic and aseismic slip evolution and deformation associated with the 2009-2010 northern Malawi earthquake swarm, East African Rift
Abstract
Interferometric synthetic aperture radar (InSAR) measurements, field observations and elastic modelling of the 2009-2010 Karonga (northern Malawi) earthquake swarm reveal widespread coseismic and localized post-seismic deformation. In a period of about 1.5 months starting on November 5, 29 M ≥ 4 earthquakes struck the region, culminating in an Mw 6 peak event on December 19. The next few months were characterized by significant localized deformation with a very low seismic moment release. We find a very good agreement between InSAR and field observations of surface ruptures. Our best fitted coseismic models indicate dip-slip displacements on a fault dipping 40° to the southwest with maximum slip of about 120 cm at 3-5 km depth. Fault activity continued until 2010 August as shallow aseismic afterslip mostly above the maximum coseismic slip patches. Although the swarm occurred within a coastal plain covered by porous Quaternary sediments and a high water table, the effect of poroelastic relaxation on the post-seismic deformation was found to be negligibly small. In contrast with other recent earthquake swarms along the East African Rift, the Karonga swarm shows no evidence for dike intrusion.
- Publication:
-
Geophysical Journal International
- Pub Date:
- December 2012
- DOI:
- 10.1111/j.1365-246X.2012.05673.x
- Bibcode:
- 2012GeoJI.191..898H
- Keywords:
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- Satellite geodesy;
- Transient deformation;
- Seismicity and tectonics;
- Continental tectonics: extensional;
- Africa