Abstract
The seismic quality factor (Q) is an important physical parameter to characterize seismic wave attenuation. Therefore, analyzing its spatiotemporal variation is essential to better understand tectonic activity, characterize earthquake source mechanisms, and assess seismic hazards. In this study, we used a single-scattering model to calculate Q for coda waves (Qc values) generated by earthquakes with epicentral distances <100 km and magnitudes M > 2.0 recorded in 2000–2023 in the northeastern margin of the Qinghai–Tibet Plateau (the study area). The calculated dependence of Qc on the bandpass filter central frequency f in the study area was ({Q}_{c}=left(72.40pm 9right){f}^{left(1.10pm 0.06right)}), ({Q}_{c}=left(100.95pm 15right){f}^{left(1.03pm 0.07right)}), and ({Q}_{c}=left(128.76pm 20right){f}^{left(0.97pm 0.07right)}) within lapse-time windows of length 20, 30, and 40 s, respectively. To estimate Qc in distinct active tectonic and fault regions, we divided the study area into two subregions, the Haiyuan and Qinling active tectonic zones. We determined a strong spatial correlation between the Qc distribution and tectonic activity in the study area, with correspondingly low Qc values. Finally, by analyzing the temporal evolution of Qc, we established that nearly all strong earthquakes (M > 6.0) that occurred in the study area in 2000–2023 were preceded by a 10–27% decrease in Qc values, a phenomenon possibly related to the ‘rock dilatancy’ theory.