资源环境科技发展态势分析平台

Earthquake radiation is broadband, and its temporal evolution carries the seismic signature of the rupture process. I use established and develop new observational metrics to quantify the temporal variation in radiated energy (seismic power) and in a time-dependent scaled radiated energy. Universal functional forms of moment rate, seismic power, and scaled energy arise from a global database of source time functions. Earthquakes radiate mostly and most efficiently in the early stage of development of the rupture that is in the first 10-30% of the overall rupture duration. This result is independent of earthquake magnitude, depth, and focal mechanism. Beyond depth dependence in elastic properties with depth that explain variations in source duration and radiated energy, subtle differences in functional forms exist between shallow and deep earthquakes. Deep events have a slower development than shallow earthquakes, but they carry a higher peak in seismic power.

Plain Language Summary When earthquakes occur, they release slip and excite ground motions. A large slip controls the low-frequency ground motions, but it is heterogeneity of rate of slip that generates the damaging ground motions. This study provides new approaches to systematically explore the temporal evolution of the high-frequency ground motions at the source and deduce a source productivity to excite the high-frequency seismic waves. I use a global database of earthquake source time functions to show that an early growth phase, which occurs in the first 10-30% of the rupture duration, is highly effective at generating seismic waves. Deep earthquakes are slower at developing but emit more ground motions overall.