Recent observations and new frontiers in seafloor geodesy

Noel M. Bartlow, David Chadwell, Laura M. Wallace, Ryan Yohler, David A. Schmidt, Mark A. Zumberge, Spahr Webb, & Andrew Newman

Submitted August 15, 2019, SCEC Contribution #9877, 2019 SCEC Annual Meeting Talk on Tue 0900

In recent years, a number of multi-instrument seafloor geodesy deployments have been successfully carried out in Japan, New Zealand, Cascadia, Alaska, and elsewhere using both GNSS-Acoustic (GNSS-A) and Absolute Pressure Gauge (APG) instruments. GNSS-A instruments measure horizontal displacements to within 1-2 cm, while APGs are used to measure vertical displacements within similar precision, albeit with long-term drift. In Japan, GNSS-A instruments recorded critical near-trench displacements following the 2011 Tohoku-oki earthquake (Sato et al., 2011), and more recently GNSS-A has been used to constrain the shallow locking in the Nankai subduction zone (Yokota et al., 2016). In New Zealand, the Hikurangi Ocean Bottom Investigation of Tremor and Slow Slip (HOBITSS) array of APG instruments recorded a slow slip event (SSE) in 2014. The APG recordings imply that slip appears to propagate to within ~2 km of the seafloor, although it isn’t possible to say whether or not it went to the trench (Wallace et al., 2016). Additionally, the APG data tighten the overall range of plausible slip potency in the 2014 SSE (Yohler et al., 2019). In Cascadia and Alaska, recent deployments of GNSS-A instruments will be used to constrain shallow locking. Early data from the Cascadia GNSS-A instruments are consistent with strong near-trench locking (Chadwell et al., AGU fall meeting 2018). Multiple experiments are currently underway in New Zealand to acquire a variety of seafloor and subseafloor geodetic data, targeted at investigating slow slip and locking on the Hikurangi subduction zone. New advances in GNSS-A and APG technology, including the use of wave gliders, have brought costs down enabling wider use of these instruments. Multiple techniques have been developed to create self-calibrating APG instruments which reduce long-term drift significantly (Sasagawa et al., 2013; Sasagawa et al;, 2018; Wilcock et al., AGU fall meeting 2018). Additional types of seafloor geodetic instruments are also in development, including optical fiber strainmeters (Zumberge et al., 2018). This talk will give an overview of these recent deployments, the recent technological advances in seafloor geodetic instrumentation, future directions, and community engagement aimed an expanding the number of researchers with access to these instruments.

Key Words
seafloor geodesy, geodesy, GPS-A, GNSS-A, absolute pressure gauge

Citation
Bartlow, N. M., Chadwell, D., Wallace, L. M., Yohler, R., Schmidt, D. A., Zumberge, M. A., Webb, S., & Newman, A. (2019, 08). Recent observations and new frontiers in seafloor geodesy. Oral Presentation at 2019 SCEC Annual Meeting.


Related Projects & Working Groups
Tectonic Geodesy