Comment on nhess-2022-228

Abstract

Accurate and rapid assessment of seismic intensity after a destructive earthquake is essential for efficient early emergency response. Here, we propose an improved method for assessing seismic intensity by analysing aftershock sequences that occur within 2 h of mainshock. The implementation and specific utilisation of the method were demonstrated using specific earthquake examples. Then, the conditions for the application of the method were summarised based on the results of 59 earthquake events that occurred globally during 2000–2022. Very early aftershocks could roughly characterise the basic features of the mainshock rupture. The curve fitted to the aftershock sequence using the robust locally weighted regression programme (Lowess) was very close to the surface rupture in the linear directional mean. The Lowess-fitted curve showed that the aftershocks distributed at some distance from the tips of the fault may have been generated at very early stages of the earthquake. The results of Lowess were closer to the fault rupture situation when Mw ≥7.0 and aftershock numbers were 40–100. Aftershock catalogues obtained by conventional means are steadily to assess the seismic intensities within 1.5 h. When the aftershock numbers were large enough, the intensity assessment time could be greatly reduced. The ground motion attenuation model provided best values at Mw ≥7.5. Our work exploits early accessible data more efficiently by extending the data sources for seismic intensity assessment and is a significant reference point for exploring the relationship between early aftershock events and faults planes.