Determination of rupture directivity of the 2024 Feidong M4.7 earthquake using one 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 M 4.7 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 M 4.7 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 M 3 earthquakes in the Feidong sequence. Our study highlights the superior application of near-source observations in earthquake source studies.