Characteristics of airplane-induced ground motion recorded by three-component(3-C) geophone and distributed acoustic sensing (DAS) in cities

Abstract:

In urban areas, characterizing and developing reliable catalogs of different kinds of anthropogenic seismicity (e.g. induced by road traffic, airplane, quarry blast) are important for probing the near-surface Earth’s structure and understanding its dynamics and interactions between air and the solid earth.

We report on the observed airplane signals recorded by a joint 3-C geophone and microphone array in Singapore and a DAS array in Pennsylvania, United State. Both the arrays are deployed in urban environments. Time-frequency analysis reveals clear Doppler effects of airplane in the spectrograms of all the recordings. We obtain airplane flight parameters by fitting the Doppler effects. We can obtain an approximation of the spatial variation of the transmission coefficient by deconvolving the sound wave of airplane from the induced seismic signals. (See figure 1)

The ground motion signals induced by airplane can be identified in the 25-300 Hz frequency band in the spectrogram of all the recordings. In 3-C geophone recordings, the vertical ground motion is stronger than horizontal motions. The DAS data shows similarity to the horizontal components of geophone data. The times of repeated airplane signals from DAS data are coincident well with the flight times at the nearby airport.

Our investigation of the airplane-induced ground motions observed by three-component geophones and DAS suggests potential applications for real-time aircraft detection and track. As an emerging technology, DAS shows its strong potential for multi-purpose monitoring in urban environments.

Figure 1. The spectrograms of (a) audio and (b) geophone Z-component, (c) E-component and (d) N- component. (e) The Dopple effect of airplane in DAS data and the estimated flight parameters. (f) Deconvolving the acoustic signals from the vertical geophone signals at all stations. The blue solid line denotes the average value of the dashed lines.