Geodetic Precursory Patterns as Preparatory Phases of the 2010, 2020, 2023 Earthquakes Along the East Anatolian Fault Zone Using Seismo- geodetic Data Analysis

15th General Assembly of Asian Seismological Commission, Antalya, Türkiye, 3 - 07 Kasım 2024, ss.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.