15th General Assembly of Asian Seismological Commission, Antalya, Turkey, 3 - 07 November 2024, pp.174-175
Abstract: The latest seismic phenomenon, 6th February 2023 in the Maras Triple Junction
(MTJ) area of the Anatolian diagonal, catastrophic earthquake doublets (Mw 7.8, 7.7), raises a
series of outstanding questions of whether these doublets are progressively preceded by geodetic
precursory anomalies and/or preparatory phases linked with the 2010 and 2020 earthquakes along
the EAFZ, of whether both events are geodetically expanded and dissipated through subsequent
aftershocks into a large volume at regional scale, and of how the 2023 seismic activation is
evolved from multiple faulting along the EAFZ and MTJ to the plate-scale seismic and geodetic
phenomenon. To answer these questions requires a plate-scale understanding of this phenomenon
and makes it necessary to consider and analyse the fifteen years-long (2009-2023) earthquake
transients and the GPS velo-city field-derived strain-displacement propagation patterns using
Continuously Operating Reference Stations-Turkey (CORS-TR, TUSAGA-Aktif), Global
Navigation Satellite Systems (GNSS) obser-vations over a large spatial extent in the Anatolian
diagonal, to obtain a reliable explanation of a long-term strain-displacement accumulation prior
to the 2023 events. The analysis is well comple-mented by well-constrained fault focal solutions
resolved from regional Centroid Moment Tensor (CMT) inversion for located 41 aftershock
events (Mw 3.7-5.3) recorded by Kandilli Observatory and Earthquake Research Institute
(KOERI) during seven months since the 2023 mainshocks onset. The key results conclude that
geodetic patchy structure and precursory field variation of asymmetric strain-displacement
accumulation patterns accompanied by the 2010 and 2020 seismic sequences drive the
preparatory process of the 2023 events as well as the 2010 and 2020 events, adjust the strain budget
of the EAFZ and unravel an evolutionary process of the Anatolian extrusion to the W. The
conclusion is complemented by the off-fault aftershock CMT solutions that characterize
interactively repeated and widely distributed strike-/oblique-slip faulting patterns (~15 km
centroid depth) in a large volume at regional scale, which lead to ongoing plate-scale
reorganization to accommodate the Anatolian extrusion to the W. Geodetic pattern structure and
CMT solutions reveal a large-scale stra-in-expanding and -accommodating area through a wide
diffuse deformation zone embedded within the Anatolian diagonal. The 2023 seismic sequence
shifted plate motions, disrupted previously exis-ting strain patterns, redistributed crustal stressstrain,
and portrayed plate-scale, diffuse aftershock deformation across the Anatolian diagonal.