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High interseismic coupling in the Eastern Makran (Pakistan) subduction zone

Lookup NU author(s): Professor Zhenhong Li

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Abstract

Estimating the extent of interseismic coupling along subduction zone megathrusts is essential for quantitative assessments of seismic and tsunami hazards. Up to now, quantifying the seismogenic potential of the eastern Makran subduction zone at the northern edge of the Indian ocean has remained elusive due to a paucity of geodetic observations. Furthermore, non-tectonic processes obscure the signature of accumulating elastic strain. Historical earthquakes of magnitudes greater than 7 have been reported. In particular, the 1945 Mw8.1 earthquake resulted in a signicant tsunami that swept the shores of the Arabian Sea and the Indian Ocean. A quantitative estimate of elastic strain accumulation along the subduction plate boundary in eastern Makran is needed to confront previous indirect and contradictory conclusions about the seismic potential in the region. Here, we infer the distribution of interseismic coupling on the eastern Makran megathrust from time series of satellite Interferometric Synthetic Aperture Radar (InSAR) images acquired between 2003 and 2010, applying a consistent series of corrections to extract the low amplitude, long wavelength deformation signal associated with elastic strain on the megathrust. We nd high interseismic coupling (i.e. the megathrust does not slip and elastic strain accumulates) in the central section of eastern Makran, where the 1945 earthquake occurred, while lower coupling coincides spatially with the subduction of the Sonne Fault Zone. The inferred accumulation of elastic strain since the 1945 earthquake is consistent with the future occurrence of magnitude 7+ earthquakes and we cannot exclude the possibility of a multi-segment rupture (Mw 8+). However, the likelihood for such scenarios might be modulated by partitioning of plate convergence between slip on the megathrust and internal deformation of the overlying, actively deforming, accretionary wedge.

Publication metadata

Author(s): Lin NY, Jolivet R, Simons M, Agram PS, Martens HR, Li Z, Lodi SH

Publication type: Article

Publication status: Published

Journal: Earth and Planetary Science Letters

Year: 2015

Volume: 420

Pages: 116–126

Print publication date: 15/06/2015

Online publication date: 08/04/2015

Acceptance date: 18/03/2015

ISSN (print): 0012-821X

ISSN (electronic): 1385-013X

Publisher: Elsevier BV

URL: http://dx.doi.org/10.1016/j.epsl.2015.03.037

DOI: 10.1016/j.epsl.2015.03.037

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