Sub- and super-shear ruptures during the 2023 Mw 7.8 and Mw 7.6 earthquake doublet in SE Türkiye

Abstract

An earthquake doublet (Mw 7.8 and Mw 7.6) occurred on the East Anatolian Fault Zone (EAFZ) on February 6th, 2023. The events produced significant ground motions and caused major impacts to life and infrastructure throughout SE Türkiye and NW Syria. Here we show the results of earthquake relocations of the first 11 days of aftershocks and rupture models for both events inferred from the kinematic inversion of HR-GNSS and strong motion data considering a multi-fault, 3D geometry. We find that the first event nucleated on a previously unmapped fault before transitioning to the East Anatolian Fault (EAF) rupturing for ~350 km and that the second event ruptured the Sürgü fault for ~160 km. Maximum rupture speeds were estimated to be 3.2 km/s for the Mw 7.8 event. For the Mw 7.6 earthquake, we find super-shear rupture at 4.8 km/s westward but sub-shear eastward rupture at 2.8 km/s. Peak slip for both events were as large as ~8m and ~6m, respectively.

Slip distribution of the February 6, 2023 Mw 7.8 and Mw 7.6, Kahramanmaraş, Turkey earthquake sequence in the East Anatolian Fault Zone

“…The Mw 7.8 mainshock initiated on the Narlı Fault Zone that bounds the Narlı basin, north of the Karasu trough (Figures 1 and 2). The rupture continued along the East Anatolian Fault, propagating bilaterally into the Amanos segment to the south and into the Pazarcık and Erkenek segments to the north (Melgar et al, 2023). The surface rupture stopped just northeast of the Yarpuzlu restraining bend.…”

“…The Mw 7.6 aftershock nucleated in the middle of the Çardak Fault and propagated westward to the Savrun Fault and eastward across the so-called Nurhak complexity (Duman and Emre, 2013) along an immature fault between the Malatya and the Sürgu faults (Melgar et al, 2023). The Mw 7.6 aftershock triggered a sequence of additional aftershocks including normal faulting earthquakes near the Savrun Fault (Figure 1).…”

“…Previous large earthquakes in this section include the 1114 M 6.9, 1795 Mw 7.0, 1872 Mw 7.2, and 1893 Mw 7.1 ruptures (Ambraseys, 2009;Güvercin et al, 2022), all bounded by major (releasing) fault bends (Duman and Emre, 2013). Since then, the fault has remained mostly locked, slowly accumulating stress, until it finally unzipped in a continuous rupture in 2023, generating a powerful Mw 7.8 earthquake (Dal Zilio and Ampuero, 2023;Melgar et al, 2023).…”

Transient, accelerating slow slips drive the Preparatory Process of the 2023 Mw 7.8 Türkiye Earthquake

“…Then, the rupture propagated to the Pazarcık segment and proceeded first northwards on the Pazarcık and Erkenek segments and then southwards on the Amanos segment (Supplementary Fig. S1) 14,16,18 . Worth to mention, the Mw 7.8 event broke a main asperity on the Pazarcık segment in proximity of the hypocenter [14][15][16]18 Looking at the recent past seismic activity in the region, the most significant earthquake was the January 2020 Mw 6.8 Elazığ earthquake 8,[20][21][22][23] , which took place in the northern part of the EAF.…”

“…S1) 14,16,18 . Worth to mention, the Mw 7.8 event broke a main asperity on the Pazarcık segment in proximity of the hypocenter [14][15][16]18 Looking at the recent past seismic activity in the region, the most significant earthquake was the January 2020 Mw 6.8 Elazığ earthquake 8,[20][21][22][23] , which took place in the northern part of the EAF. The latter earthquake was mainly a left-lateral strike-slip, with a small portion of source slip presenting a down-dip behavior 22 .…”