Determination of rupture directivity of the 2024 Feidong M4.7 earthquake using single near-source station

Determining the rupture directivity for small earthquakes is challenging due to the small source dimension and limited resolution of far-field observations. In recent years, the burst of near-source observations provides great opportunities to study earthquake rupture. Here we present the rapid determination of the rupture directivity for the 2024 Feidong M4.7 earthquake using only one strong motion station located 4 km from the epicenter. We find that the polarization of S waves evolves during the rupture, indicating an azimuth change during the rupture propagation. Through comparing the data with the synthetic waveforms, we infer that the M4.7 event propagated dominantly to the southwest on the dextral Tanlu fault. Our inference is further validated through comparing the data with records at local stations for M3 earthquakes in the Feidong sequence. Our study highlights the superior application of near-source observations in earthquake source studies.