Suli Yao, Hongfeng Yang

Understanding and deciphering wiggles especially coherent phases from seismograms have been a long endeavor to understand the earth structure and earthquake source. However, coherent phases directly associated with earthquake rupture propagation have not been available due to the lack of continuous near-fault observations. Here we report the rupture phase as large velocity pulses during the 2023 Mw 7.8 Turkey earthquake. Through data analysis and numerical rupture simulations, we estimate the rupture speed to be subshear (i.e. ~3.1-3.4 km/s) along the southern segment of the East Anatolian Fault. Moreover, we constrain the critical slip distance (D_c) to be ~ 1.35 m in average, 60% of the reported average surface slip. With the expanding coverage of near-fault observation network, such rupture phases in future earthquakes can be used to unravel rupture process and frictional properties on faults.