The PIs will deploy an autonomous underwater hydrophone (AUH) network in conjunction with OBSs in the Lau Basin. Since T-wave generation processes are not well understood the PIs will use the AUH and the OBSs to compare and establish how to integrate the datasets, allowing them to constrain the tectonics of the region and monitor both earthquake activity and volcanism. The comparison will allow future hydrophone data to be used to extract quantitative information regarding earthquake source parameters and processes. Broader impacts include collecting both the seismically-generated signals and whale songs which will be used in the proposed development of a K-12 curriculum module that includes the building of a hydrophone. There is also graduate and undergraduate student participation and continued public outreach by the PIs at local, national, and international levels.
This project investigated the seismo-tectonics of the Eastern Lau Spreading Center and Tofua volcanic arc, as well as studied the physics of Tertiary (T) wave generation using data from both hydroacoustic and seismic sensors. We not only captured the spectacular eruption of Hunga Ha’apai volcano in March of 2009, but also provided the first evidence that oceanic arc volcanoes respond to dynamic stress changes following great earthquakes. Using available air-gun sources, we quantified the contribution of topography and seafloor roughness in controlling the amplitude and duration of acoustic arrivals within the basin. We also conducted the first hydroacoustic survey of an erupting volcano using an autonomous underwater glider platform, as well as conducted shorter-term deployments of hydrophones around the erupting West Mata volcano. Additionally, we performed a comparative study between the location capabilities of ocean bottom seismic and autonomous underwater hydrophone sensor networks along the Eastern Lau Spreading Center and identified an active zone of deep-seafloor seismo-volcanic activity in the area between the Tofua arc and spreading center. This grant has partially supported four graduate students and provided sea-going experience for a total of five graduate students in the marine and earth sciences. In addition, a total of eight undergraduates from NC State University and Wake Tech Community College were involved in the analysis of the data collected through this project. Our work has led to technical advances in precision time keeping using pulse-per-second (PPS) and inductive modem techniques. All hydroacoustic waveform data and associated meta-data have been achieved permanently within the National Science Foundation’s Marine Geoscience Data System.
