EAR-PF Investigating Volcanic Explosion Directivity Using Aerial Infrasound Observations with UAVs

Iezzi, Alexandra Michelle, Fairbanks AK

Investigators

Abstract

Dr. Alexandra Iezzi has been granted an NSF EAR Postdoctoral Fellowship to carry out research and educational activities at the University of California Santa Barbara under the mentorship of Professor Robin Matoza. Infrasound sensors measure low-frequency acoustic waves (below the limit of human hearing) and provide a detailed means to monitor and characterize explosive sources such as those caused by volcanic eruptions. However, these sensors are usually placed on the Earth's surface, providing only a limited sampling of the acoustic radiation pattern and directionality of volcanic explosions creating a bias in how acoustic sources are characterized. This project addresses this issue by using a novel approach of collecting infrasound data with sensors aboard multiple unmanned aerial vehicles (UAVs) in addition to traditional sensor deployments on the ground. Our sensor platform and measurements will increase our understanding of acoustic directivity at the frequently active Yasur volcano, in Vanuatu and for explosive sources in general. The research proposed here has the potential to revolutionize the way active volcanoes are monitored using infrasound instrumentation aimed at providing unique information on explosion dynamics. The new techniques proposed will allow infrasound sensors to be deployed both in the air and on the ground close to the eruption, so that a volcanic source is understood better with significantly reduced risk exposure to field personnel. This project is a proof-of-concept study of UAV-based infrasound deployments that can extend data collection to previously unreachable locations near active volcanoes and anthropogenic explosion sources around the world. The UAV-mounted infrasound sensors will record data from unique angles, allowing for acoustic source inversion methods that account for the effects of topography to constrain the directional radiation pattern of explosions in a way not previously possible. By following these methods, we will also improve the calculation of the mass flow rate, which is an invaluable parameter for monitoring. The infrasound observations will be validated with ballistic trajectories determined from multiple cameras deployed around the crater rim, which we assume to be similar to the directionality of ash, gas, and steam emissions that may present harm to those near the volcano. Configuring UAV-mounted infrasound sensors in a vertical line above one of the crater rim stations will, for the first time, allow us to investigate the precise vertical location of the infrasonic source. Finally, we will create a prototype and test a UAV infrasound sensor deployment where the sensor is flown to an inaccessible area, dropped off, and retrieved by the UAV. This technique can be applied for future monitoring during times of eruption crises. As part of the broader impacts of this project Dr. Iezzi will teach a reading seminar course and design a demonstration mimicking the usage of UAVs around Yasur volcano entitled “trashcano”, which is sure to catch middle-school students’ interest. Outreach activities include a photo-journal from Yasur volcano to share with local teachers and thus expanding outreach educational efforts. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.