The Seismology Laboratory of the Department of Geophysical Engineering sheds light on the rupture kinematics of the two devastating earthquakes that occurred in Kahramanmaraş, SE Turkey

In a significant contribution to earthquake research, particularly after the 2023 Earthquake doublet in Kahramanmaraş, members from the Seismology Laboratory of the Department of Geophysical Engineering have recently published several research articles in high-impact journals as well as rapid earthquake reports. These publications do not only underscore the expertise of the Seismology Laboratory but also provide valuable insights into the seismic activity in the region, contributing to the broader understanding of earthquake processes. Recent findings from the research group sheds light on the rupture kinematics of the two devastating earthquakes that occurred in Kahramanmaraş, SE Turkey.

Complex multi-fault rupture and triggerig during the 2023 earthquake doublet in southeastern Türkiye

by Chengli Liu, Thorne Lay, Rongjiang Wang, Tuncay Taymaz, Zujun Xie, Xiong Xiong, Tahir Serkan Irmak, Metin Kahraman & Ceyhun Erman

NATURE Communications, Vol. 14, 5564(2023), NCOMMS-23 18990. https://doi.org/10.1038/s41467-023-41404-5, Published Online 9 September 2023.

Abstract: Two major earthquakes (MW 7.8 and MW 7.7) ruptured left-lateral strike-slip faults of the East Anatolian Fault Zone (EAFZ) on February 6, 2023, causing > 59,000 fatalities and ~$119B in damage in southeastern Türkiye and northwestern Syria. Here we derived kinematic rupture models for the two events by inverting extensive seismic and geodetic observations using complex 5-6 segment fault models constrained by satellite observations and relocated aftershocks. The larger event nucleated on a splay fault, and then propagated bilaterally ~350 km along the main EAFZ strand. The rupture speed varied from 2.5-4.5 km/s, and peak slip was ~8.1 m. 9-h later, the second event ruptured ~160 km along the curved northern EAFZ strand, with early bilateral supershear rupture velocity (>4 km/s) followed by a slower rupture speed (~3 km/s). Coulomb Failure stress increase imparted by the first event indicates plausible triggering of the doublet aftershock, along with loading of neighboring faults.

a Black thick lines show the main active faults (NAFZ North Anatolian Fault Zone, EAFZ East Anatolian Fault Zone, SF Sürgü fault, DSF Dead Sea Fault, EPF Ezine Pazari Fault, TGF Tuz Gölü Fault, MF Malatya Fault). Bold red lines denote the approximate rupture extent of historical events. Red K indicates the Karlıova triple junction and red İ represents İskenderun Bay. Red and green stars indicate the epicenter of the MW 7.8 and MW 7.7 earthquakes, respectively. Black thick arrows show the direction of motions between plates. The gray dashed rectangle outlines the source region of the 2023 Türkiye earthquake doublet. b Cyan-filled circles with a radius proportional to magnitude show the relocated aftershocks with M > 1.0. The red, green, and gray stars indicate the locations of the 2023 Türkiye earthquake doublet and the 2020 Doğanyol-Sivrice MW 6.7 event, respectively, from the AFAD-DDA catalog, and the corresponding focal mechanisms are USGS-NEIC W-phase solutions. The red lines represent fault ruptures indicated by post-earthquake satellite data33. Black thin lines represent active faults. The blue diamonds indicate the position of the two candidate triple junctions (MTJ Maras triple junction, ATJ Amik triple junction). Labeled magenta squares indicate the major cities around the source region (taken from Liu et al., 2023).

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Geometric controls on cascading rupture of the 2023 Kahramanmaraş earthquake doublet Türkiye

by Yijun Zhang, Xiongwei Tang, Dechuan Liu, Tuncay Taymaz, Tuna Eken, Rumeng Guo, Yong Zheng, Jingqi Wang & Heping Sun

NATURE Geoscience, Vol. 16, 1054-1060(2023), NGS-2023-04-00727. https://doi.org/10.1038/s41561-023-01283-3, Published Online 12 October 2023.

Abstract: How fault geometry controls the rupture propagation and segmentation of a strike-slip event is an open question. Deciphering the relationship between the geometric fault complexity and seismic kinematics is essential for both understanding the seismic hazard posed by a particular fault and gaining insights into the fundamental mechanics of earthquake rupture. Here we integrate the finite-fault inversion of synthetic aperture radar observations and back projection of high-frequency teleseismic array waveforms to investigate the rupture geometry of the 2023 M_w 7.8 and M_w 7.6 Kahramanmaraş (southeastern Turkey) earthquake doublet and its impact on the kinematics and slip distribution. We find that large slip asperities are separated by fault bends, whereas intense high-frequency (~1 Hz) sources occur near the branching junctions, suggesting that geometric barriers could decelerate rupture propagation and enhance high-frequency wave radiations. In addition, supershear rupture propagating along the relatively high-velocity material is prone to occur on geometrically simple and smooth faults with relatively few aftershocks. These kinematic characteristics highlight that the geometric complexity of the fault system may be a key factor in the irregular cascading rupture process.

Inversion results in a three-dimensional perspective.

a, Fault slip distribution estimated from InSAR observations. b, Shear-stress changes on fault patches, where red values indicate stress increase and blue values indicate stress drop. c, Sinistral slip amplitudes. d, Slip along the dip. Positive (red) and negative (blue) values mean normal and reverse slip, respectively (taken from Zhang et al., 2023).

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Sub- and Super-Shear Ruptures During the 2023 Mw 7.8 and Mw 7.6 Earthquake Doublet in SE Türkiye

by Diego Melgar, Tuncay Taymaz, Athanassios Ganas, Brendan W. Crowell, Taylan Öcalan, Metin Kahraman, Varavara Tsironi, Seda Yolsal-Çevikbilen, S. Volkaniotis, Tahir Serkan Irmak, Tuna Eken, Ceyhun Erman, Berkan Özkan, Ali Hasan Doğan, Cemali Altuntaş

SEISMICA, Vol. 2(3). https://doi.org/10.26443/seismica.v2i3.387, Published Online 13 March 2023.

Abstract: An earthquake doublet (Mw 7.8 and Mw 7.6) occurred on the East Anatolian Fault Zone on Febru- ary 6th, 2023. The events produced significant ground motions, in excess of 150%g, and caused major impacts to life and infrastructure throughout SE Türkiye and NW Syria. Here we show the results of earthquake reloca- tions of the first 11 days of aftershocks and rupture models for both events inferred from the joint kinematic inversion of HR-GNSS and strong motion data considering a multi-fault and 3D rupture 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. Maximum slip for both events were as large as ~8 m and ~6 m, respectively.

The animation shows the rupture propagation for both events. Plotted is the slip rate, which then fades into the final slip. Inset are the source time functions for both events (taken from Melgar et al., 2023).

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