资源环境科技发展态势分析平台

In this study we analyze infrasound signals from three earthquakes in central Italy. The M-w 6.0 Amatrice, M-w 5.9 Visso, and M-w 6.5 Norcia earthquakes generated significant epicentral ground motions that couple to the atmosphere and produce infrasonic waves. Epicentral seismic and infrasonic signals are detected at I26DE; however, a third type of signal, which arrives after the seismic wave train and before the epicentral infrasound signal, is also detected. This peculiar signal propagates across the array at acoustic wave speeds, but the celerity associated with it is 3 times the speed of sound. Atmosphere-independent backprojections and full 3-D ray tracing using atmospheric conditions of the European Centre for Medium-Range Weather Forecasts are used to demonstrate that this apparently fast-arriving infrasound signal originates from ground motions more than 400 km away from the epicenter. The location of the secondary infrasound patch coincides with the closest bounce point to I26DE as depicted by ray tracing backprojections.

Plain Language Summary Underground explosions and earthquakes generate ground motions at the surface of the Earth and induce pressure fluctuations in the atmosphere. These fluctuations propagate through the atmosphere as inaudible sound called infrasound and are detected by pressure sensors hundreds of kilometers away. In this paper, we discuss how these detections can reveal information about the regions in which seismic energy radiated from underground sources couples to the atmosphere and generates infrasound. We convey a new understanding of this process and demonstrate that infrasound may originate from a much larger region and much farther away from the source than previously described in the scientific literature. Understanding the interaction of these two wavefields, seismic and infrasonic, is important for monitoring nuclear explosions, for example, but can also be used to evaluate the state of the atmosphere from naturally occurring sources like earthquakes and volcano eruptions.