MRI: Development of a Telemetered Seafloor Seismic Observatory (TeSSO)

A traditional ocean bottom seismometer (OBS) is deployed from a ship, settles on the seafloor, and then records signals from earthquakes and other seismic events. The recording occurs remotely and autonomously, where the scientist has no access to the data until the instrument is recovered during a follow-up station visit. Often, a scientist has to wait for more than a year to analyze the collected data. For earthquake and tsunami monitoring purposes, this is much too long to conduct useful, and often critical, short-fuse research. This project, will engineer an acoustic modem gateway between the OBS and a wave glider on the sea surface to ultimately transmit data from the seafloor all the way to the desktop of a data analyst in near-real time. The OBS will transmit low-rate data (1 sample per second) to shore continuously. A novel engineering aspect of this project will be the possibility of two-way traffic, i.e. a data analyst can request a snipped of high-rate data (50 samples per second) immediately after an interesting event. A new-generation high-quality seismic sensor will be used on the newly developed shielded OBS package that will allow the recording of seismic signals from the tidal band (several hours) to high frequencies limited only by the sampling rate. The shielding of the seismic sensor will significantly reduce ambient noise contamination caused by deep-ocean currents. Ultimately, the new technology will provide a stepping stone to a long-duration (several years) multi-node mini array of OBS's on the seafloor, serviced by several concurrent wave gliders that visit stations in turn to transmit data back to shore. This project will focus on the design, construction and testing of a Telemetered Seafloor Seismic Observatory (TeSSO) comprising a very-broadband ocean bottom seismometer and a differential pressure gauge. The SSO will be equipped with an acoustic micromodem and is linked through a wave glider that facilitates a Surface Communications Gateway (SCG) with shore-side mission control via acoustic and satellite services. The wave glider will cruise on the surface and relay buffered 1 sps data from the SSO via satellite to shore-side mission control. A new two-way data traffic capability will allow shore-side researchers to order specific higher sample-rate data snippets (50 sps) in case an interesting earthquake or other seismogenic event occurs. This project draws on past expertise gathered from the 2013 ADDOSS project that provided wave-glider-based near-real time access in a one-way fashion, where the ocean bottom seismometer sent data autonomously. Since then, significant improvements in technology (e.g. 3rd generation wave glider, low-power broadband seismometers, and ‘smart’ data loggers) have occurred. The realization of TeSSO relies critically on engineering design and development to assemble off-the-shelf components. Two short sea trials will help optimize the instrument package and the SCG. On a third trial, the wave glider will transit between two close-by SSOs and transmit data on an alternating schedule. This will lay the ground work for a system of multiple SSOs that are served in near-real time by a fleet of wave gliders. TeSSO will be able to address some, but not all, items on a growing wish list compiled by data users from both the global seismic networks but also an increasing number of passive seismic deployments in the oceans 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.