Earthquakes can cause noise disturbances, such as rumbling, roaring, or even loud bangs, that people can hear, even if the earthquakes are very small and don't cause any building damage. In 2018, a geothermal energy project near Helsinki, Finland, triggered thousands of small earthquakes deep underground. Despite their small size, these earthquakes were loud enough that many people in the area heard and reported them.

We use powerful computer simulations to understand how such small earthquakes could create audible noises. These simulations allow us to model precisely how earthquake waves travel through the Earth and then into the air as sound waves. Surprisingly, we find that most of the audible noise was generated by a type of earthquake wave known as an S-wave, not the more commonly suspected P-wave. We also discover that the exact location and loudness of the noise depended heavily on the earthquake's underground source characteristics, rather than the local landscape.

Our findings show that detailed computer modeling can help scientists better understand and manage earthquake-related noises, potentially guiding practical strategies to reduce disturbances caused by earthquakes near populated areas.