Doppler Frequency Shifts Associated With the 29 July 2025 M8.8 Kamchatka Earthquake in Southwest China

Abstract The high‐frequency (HF) Doppler sounder array is a well‐established technique for monitoring vertical fluctuations in the ionospheric layer at specific altitudes. On 29 July 2025, at 23:24:50 UT, a devastative magnitude 8.8 earthquake occurred in the Far East of Russia. The phenomena of Doppler Frequency Shifts (DFSs) were observed by the HF Doppler sounder array in southwestern China at a considerable distance of approximately 5,400 km from the epicenter. Analytical results show that DFSs retrieved from arrays in China are not associated with primary (P) waves, but instead correspond well to the wave packet of secondary (S) and Rayleigh waves, with a delay of approximately 420 s. Combined Doppler data from China, Japan, and the Taiwan region further indicate that DFSs are strongly associated with the Rayleigh waves of the Kamchatka earthquake. However, signatures of these acoustic waves were neither identified in concurrent total electron content (TEC) from the ground‐based global navigation satellite system receivers nor magnetic data from magnetometers in the far‐field (southwestern China ∼5,400 km away). These results demonstrate that HF Doppler measurements provide a highly sensitive method for detecting seismo‐acoustic waves and studying lithosphere‐atmosphere‐ionosphere coupling, especially when other geophysical parameters show no discernible response.