Scaling of stress drop and high-frequency fall-off of source spectra

It has been observed for a long time that the high-frequency fall-off constant of source spectra is about 2 for "large"earthquakes and about 3 for "small" earthquakes. For earthquakes between "large" and "small", the high-frequencyfall-off constant is not an integer and varies with the size of the earthquake. In this article such a variation is explainedin the perspective of the scaling of stress drop, which proposes a new approach to the study of the scaling of stress dropusing seismic data with lower quality of completeness and high-frequency characteristics. The study on the sourcespectra of the aftershocks of the 1988 Lancang-Gengma, Yunnan, China earthquake shows that the high-frequencyfall-off of source spectra and its variation with the size of earthquake can be well explained by the model that for "large"earthquakes the stress drop is a constant while for ',small" earthquakes the stress drop increases with the size of theearthquake.