Infrasound Generated by Fluid-Induced Seismicity in Finland

Date: 4/26/2019

Time: 06:00 PM

Room: Fifth Avenue

Enhanced (or Engineered) Geothermal Systems (EGS) hold a high potential for exploiting the ubiquitous heat energy of the Earth but require stimulation of fluid-flow channels with the common by-product of triggered or induced earthquakes. To reduce the risk of damage from these earthquakes, effective monitoring systems must be deployed around drilling locations and are largely composed of seismic stations. Here we present infrasonic recordings of earthquakes generated during hydraulic-stimulation of the world’s deepest EGS located near Helsinki, Finland, in July 2018. Infrasound is defined as atmospheric acoustic waves with frequencies below 20 Hz, the lower threshold of human hearing. In response to public reports of booming noises in the surrounding area, eight infrasound microphones were rapidly deployed across two locations no further than 2.5 km from the drill site. The microphones were deployed for a total of 13 days, during which 342 earthquakes of magnitudes up to Mw 1.9 were recorded and located by the seismic monitoring system already in place. Arrival times of the infrasound waveforms suggests they were generated by stimulation of the atmosphere by seismic waves travelling past the station. This case study highlights how microphones capable of recording infrasound can complement seismic monitoring networks around current or future EGS projects.

Presenting Author: Oliver Lamb

Authors