Seafloor Pressures, Temperatures, Ocean Circulation and Plate-Interface Slow Slip

Date: 4/24/2019

Time: 09:30 AM

Room: Cascade II

Seafloor pressure measurements made above the slipping subduction zone plate-interface have elucidated transient aseismic slow fault slip. Primary evidence for slow slip has come from onshore displacement measurements made using satellite data, after removal of signals attributable to atmospheric processes. Offshore pressure data similarly require elimination of large hydrostatic pressure signals generated by variations in the height and density of the ocean water column, but only accomplished with far poorer sampling and resolution than for onshore. We demonstrate a novel approach to reduce water column and some instrumental noise from seafloor pressures. This approach is based on correlations between seafloor temperature and pressure changes recorded at the same location and the assumption that tectonic deformation affects only seafloor pressures. In this case, the signal common to both pressure and temperature changes are due to water column processes and can be estimated and removed. If recorded within a single logging system, instrumental noise also may be estimated and reduced. Relative to methods that eliminate water column signals by subtracting reference site pressures and instrumental noise by subtracting fit parametric functions, this approach does not rely on assumptions about the spatial scale of water column processes nor on availability of data from a site unaffected by the slow slip. The approach also benefits from the minimal cost, high accuracy, and ease with which temperatures are recorded. We test the assumptions and illustrate the potential and limitations of all these approaches using measurements and model calculations of seafloor temperatures and pressures from the New Zealand Hikurangi subduction zone.

Presenting Author: Joan Gomberg

Authors