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Geodetic observations of postseismic creep in the decade after the 1999 Izmit earthquake, Turkey: Implications for a shallow slip deficit
Author(s) -
Hussain Ekbal,
Wright Tim J.,
Walters Richard J.,
Bekaert David,
Hooper Andrew,
Houseman Gregory A.
Publication year - 2016
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.983
H-Index - 232
eISSN - 2169-9356
pISSN - 2169-9313
DOI - 10.1002/2015jb012737
Subject(s) - geology , interferometric synthetic aperture radar , seismology , creep , geodesy , geodetic datum , slip (aerodynamics) , north anatolian fault , fault (geology) , classification of discontinuities , seismic gap , vertical displacement , crust , tectonics , induced seismicity , synthetic aperture radar , geophysics , remote sensing , geomorphology , mathematical analysis , materials science , physics , mathematics , composite material , thermodynamics
The relationship between aseismic slip and tectonic loading is important for understanding both the pattern of strain accumulation along a fault and its ability to generate large earthquakes. We investigate the spatial distribution and temporal evolution of aseismic creep on the western North Anatolian Fault (NAF) using time series analysis of Envisat interferometric synthetic aperture radar (InSAR) data, covering the full extent of the 1999 Izmit and Düzce earthquake ruptures and spanning 2002–2010. Discontinuities in the line‐of‐sight velocity across the fault imply that fault creep reaches the Earth's surface at an average fault‐parallel rate of ∼5 mm/yr along an ∼80 km section of the NAF. By combining InSAR and published GPS velocities, we are able to extract the vertical and east‐west components of motion and show that the Adapazari basin is subsiding at a rate of ∼6 mm/yr. Vertical motions have biased previous estimates of creep in this region. The displacement time series close to the fault is consistent with an afterslip model based on rate‐and‐state friction, which predicts a rapid deceleration in fault creep rate after the Izmit earthquake to a near‐steady state ∼5 mm/yr after 5 years. Projecting our model 200 years into the future we find that the cumulative displacement of 1–1.3 m is insufficient to account for the shallow coseismic slip deficit observed in previous studies. Distributed off‐fault deformation in the shallow crust or transient episodes of faster slip are likely required to release some of the long‐term strain during the earthquake cycle.