Seismic Observations of Four Thunderstorms Using an Underground Fiber-Optic Array

Abstract:

Thunderstorms are known to generate acoustic/electromagnetic waves which interact with the ground surface to cause measurable ground vibration. Recordings of these seismic signals can be used to study the movement and lightning activity within thunderstorms, as well as leading to a better understanding of atmosphere-lithosphere coupling and a potentially good source of seismic waves for subsurface imaging.

Distributed acoustic sensing (DAS) is an ideal tool for thunderstorm studies as it is highly sensitive and allows for constant monitoring and dense sampling in a large, low impact array. In this study, we use the Penn State FORESEE array in State College, PA, to expand on preliminary work by Zhu and Stensrud (2019) and present substantial thunderstorm data from four dates ranging from May to September 2019. The full waveform and frequency content of the signal shows recognizable features of thunderquakes and is easily comparable to equivalent seismometer data. We use a time-domain grid search and modified Geiger’s method to obtain the back azimuth and slowness of the waves, and to pinpoint source locations where the thunderstorms interact with the ground surface. Correlated with the time of the recorded signal, this data allows reconstruction of thunderstorm movement, as well as offering some insight into subsurface velocity.