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.
Our goal was to better understand the processes involved in deep-ocean volcanic and earthquake activity in the Lau basin, an under-water volcanic area between New Zealand and American Samoa. We deployed 16 hydrophone moorings for 18 months that recorded the under-water acoustic signals of more than 100,000 earthquakes and volcanic explosions in the area. We had several discoveries, including [1] identification of several new, previously unknown, active seafloor volcanoes, [2] we showed that the massive, September 2009 Samoan earthquake caused several volcanoes in the region to increase their volcanic explosion activity. Our research helps us better understand the dynamics and interplay of submarine volcanic and earthquake activity, which aids in our efforts to mitigate volcanic, seismic, and tsunami hazards to nearby coastal communities. As part of our project, we also developed a new sensing instrument that did not previously exist, called a vertical hydrophone mooring. The vertical mooring has three hydrophones linked by a cable modem that allows the hydrophones to communication with each other. This allowed us to record underwater acoustic signals with unprecedented clarity and resolution, which greatly enhanced our research efforts. We also used seismic airgun data from another experiment that occurred during our hydrophone deployment to estimate the energy of the airgun array on the US R/V Langseth. Recently there has been concern that noise from research airguns can pose a threat to marine animals, specifically cetaceans. We found that at the distances we monitored, the airguns did not meet the "take" level for cetaceans.
