Rupture phases reveal geometry-related rupture propagation in a natural earthquake

Understanding and deciphering wiggles from seismograms has been a long endeavor to understand the internal structure of the Earth and to explore earthquake source properties. Here we make the first attempt to decipher the continuous rupture phases as large near-fault velocity pulses along the East Anatolian Fault in the 2023 Mw 7.8 Kahramanmaraş, Türkiye earthquake. With constraint from the near-fault data, we can resolve earthquake rupture details with unprecendented resolution. Through data analysis and dynamic rupture simulations, we robustly identify the transient supershear rupture on a segment with flat fault trace and rupture deceleration at fault bends. Our study highlights the complexity and superior application of near-fault data for understanding earthquake dynamics.