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Rapid Dynamic Rupture Modeling of the February 6, 2023, Kahramanmaraş, Turkey-Syria Earthquake Doublet

Description: 

The dynamically complex February 6, 2023, Turkey-Syria Earthquake sequence ruptured an unexpected set of variably oriented neighboring fault segments, complicating data-driven efforts to image and model the source processes of these devastating earthquakes. We present rapid 3D dynamic rupture simulations, verified against geodetic and seismic observations, illuminating the mechanics and dynamics of rupture complexities observed in the Kahramanmaraş doublet, which involved an initial Mw 7.8 event followed by a Mw 7.7 event ~100 km to the NNE. We provide mechanically consistent explanations of observed subshear and supershear rupture speeds, multiple slip episodes, strong ground motion pulses, and fault system interaction.

We reconcile regional seismo-tectonics, rupture dynamics, and ground motions up to 1 Hz in a geometrically complex network of ten curved fault segments subject to a heterogeneous regional stress field. We analyze the factors contributing to the doublet’s dynamics and regional ground motions, including fault geometry and the relative roles of static and dynamic triggering. The doublet’s linked dynamic rupture scenarios each match seismogeodetic observations and observed fault-system interactions. The Mw 7.8 event involved delayed, dynamically unfavorable backward branching from a steeply intersecting splay fault, which did not necessarily require supershear speeds. The asymmetric dynamics of the bilateral Mw 7.7 event arise from variations in prestress, fracture energy, and relative fault strength, which we discuss in relation to regional seismo-tectonics. The dynamics of the second event are complicated by the 3D mainshock stressing, which was too low for instantaneous dynamic triggering during the mainshock. We demonstrate that rapidly developed dynamic rupture models can explain unexpected fault system mechanics shortly after large earthquakes. Our results may help inform rapid post-event hazard assessment efforts following future earthquakes and constrain short- and long-term mechanical interactions between faults of the Eastern Anatolian Fault system and complex multi-fault systems worldwide.

Session: February 2023 Mw 7.8 Earthquake Sequence in Turkey

Type: Oral

Date: 4/19/2023

Presentation Time: 08:45 AM (local time)

Presenting Author: Thomas Ulrich

Student Presenter: No

Invited Presentation: 

Authors