ABSTRACT
In this study, we
investigated the main features of the causative fault of the 24 January 2020,
Mw 6.8 Elazığ earthquake (Turkey) using seismological and geodetic data sets
to provide new insight into the East Anatolian Fault Zone (EAFZ). We first
constrained the co-seismic surface deformation and the rupture geometry of the
causative fault segment using Interferometric Synthetic Aperture Radar (InSAR)
interferograms (Sentinel-1A/B satellites) and teleseismic waveform inversion,
respectively. Also, we determined the centroid moment tensor (CMT) solutions of
focal mechanisms of the 27 aftershocks using the regional waveform inversion
method. Finally, we evaluated the co-seismic slip distribution and the CMT
solutions of the causative fault as well as of adjacent segments using the 27
focal solutions of the aftershocks, superimposed on the surface deformation
pattern. The CMT solution of the 24 January 2020 Elazığ earthquake reveals a
pure strike-slip focal mechanism, consistent with the structural pattern and
left-lateral motion of the EAFZ. The rupture process of the Elazığ event
indicated that the rupture is started at 12 km around the hypocenter, and then
propagated bilaterally along the NE-SW but mainly toward the southwest. The
rupture slip has initially propagated toward the southwest (first 10 s) and
northeast (4 s), and again toward the southwest (9 s). Maximum displacement is
calculated as 1.3 m about 20 km southwest of the hypocenter at 6 km depth
(centroid depth). The rupture stopped to down-dip around 20 km depth toward the
southwest. The distribution of the slip vectors indicates that the rupture
continued mostly through a normal oblique movement. Most of the moment release
was released SW of the hypocenter and the rupture reached up to around 50 km.
The focal mechanisms of analyzed 27 aftershocks show strike-slip, but mostly
normal and normal oblique-slip faulting with an orientation of the tensional
axes (NNE-SSW), indicating a normal oblique-slip, “transtensional” stress
regime, parallel-subparallel to the strike of the EAFZ, consistent with
SW-rupture directivity and co- seismic deformation pattern. Finally, based on
the co-seismic surface deformation compatible with the distributional pattern
of normal focal solutions, normal and normal oblique-slip focals of the
aftershocks evidence the rupture-parallel pull-apart basin activation as a
segment boundary of the left-lateral strike-slip movement of the EAFZ.
Authors: T. Serkan Irmak, Mustafa Toker, Evrim Yavuz, Erman Şentürk, Muhammed Ali Güvenaltın
Journal: Annals of Geophysics
Year: 2021
DOI: 10.4401/ag-8638
Cite this article: Irmak, T. S., Birdem, M., Yavuz, E., Şentürk, E., Güvenaltın, M. A. (2021). New Insight into the 24 January 2020, Mw 6.8 Elazığ Earthquake (Turkey): An Evidence for Rupture-Parallel Pull-Apart Basin Activation along the East Anatolian Fault Zone Constrained by Geodetic and Seismological Data. Annals of Geophysics, 64(4).
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