Abstract:On February 6, 2023, two strong earthquakes with magnitudes of MW7.8 and MW7.5 occurred along the East Anatolian Fault Zone in southeastern Turkey. Large near-fault velocity pulses were observed during both major earthquakes occurring on the same fault zone within one day. This study investigated the characteristics of pulse-type ground motions and the effects of the source of the Turkish earthquake sequence. First, horizontal-component ground motions recorded during the two earthquakes were collected, and 28 and 8 velocity pulse records were extracted, respectively, using a wavelet-based identification algorithm. The spatial distribution characteristics of the pulse records, as well as the variations in parameters such as velocity pulse period and response spectrum amplification factors, were analyzed. By comparing these results with empirical relationships for pulse parameters, the individual characteristics of the Turkish earthquakes were discussed. Subsequently, velocity pulses observed at the same stations during both earthquakes were compared to explore the effect of source rupture process on velocity pulses. The results showed significant variations in velocity pulses of the two earthquakes, with pulse periods notably differing from previous empirical relationships due to complex source effects. The response spectrum amplification factors by pulses ranged from 1.8 to 7.5. Most pulse-recording stations were located in areas adjacent to the fault, and pulse periods exhibited increasing trends with fault distance. Source slip distribution had a significant effect on the characteristics of near-fault velocity pulses. These findings contribute to a deeper understanding of the relationship between near-fault velocity pulses and source, providing scientific references for establishing prediction models for near-fault velocity pulses and determining seismic inputs for pulse-type ground motions in earthquake-resistant engineering.
