The Deployment of the Seismometer to Investigate Ice and Ocean Structure (SIIOS) in Northwest Greenland: An Analog Experiment for Icy Ocean World Seismic Deployments

Abstract

In anticipation of future spacecraft missions to icy ocean worlds, the Seismometer to Investigate Ice and Ocean Structure (SIIOS) was funded by National Aeronautics and Space Administration, to prepare for seismologic investigations of these worlds. During the summer of 2018, the SIIOS team deployed a seismic experiment on the Greenland ice sheet situated, approximately, 80 km north of Qaanaaq, Greenland. The seismometers deployed included one Trillium 120 s Posthole (TPH) broadband seismometer, 13 Silicon Audio flight-candidate seismometers, and five Sercel L28 4.5 Hz geophones. Seismometers were buried 1 m deep in the firn in a cross-shaped array centered on a collocated TPH and Silicon Audio instrument. One part of the array consisted of Silicon Audio and Sercel geophones situated 1 m from the center of the array in the ordinal directions. A second set of four Silicon Audio instruments was situated 1 km from the center of the array in the cardinal directions. A mock-lander spacecraft was placed at the array center and instrumented with four Silicon Audio seismometers. We performed an active-source experiment and a passive-listening experiment that lasted for, approximately, 12 days. The active–source experiment consisted of 9–12 sledgehammer strikes to an aluminum plate at 10 separate locations up to 100 m from the array center. The passive experiment recorded the ice-sheet ambient background noise, as well as local and regional events. Both datasets will be used to quantify differences in spacecraft instrumentation deployment strategies, and for evaluating science capabilities for single-station and small-aperture seismic arrays in future geophysical missions. Our initial results indicate that the flight-candidate seismometer performs comparably to the TPH at frequencies above 0.1 Hz and that instruments coupled to the mock-lander perform comparably to ground-based instrumentation in the frequency band of 0.1–10 Hz. For future icy ocean world missions, a deck-coupled seismometer would perform similarly to a ground-based deployment across the most frequency bands.

The Detection of Seismicity on Icy Ocean Worlds by Single‐Station and Small‐Aperture Seismometer Arrays

“…We selected sites with thick ice (>100 m) overlying some degree of liquid water, in proximity to the abundant seismicity of an active subduction zone, or a region of low tectonic activity (stable cratonic regions). Our selected sites were Gulkana Glacier in the Alaska Range (Marusiak et al., 2020) and a site in northwest Greenland (Figure 1; Marusiak, Schmerr, et al., 2021).…”

“…For details regarding the power density functions, tilt directions, rotations, and exact geometries at the Gulkana Glacier site see Marusiak et al. (2020) and the northwest Greenland site (Marusiak, Schmerr, et al., 2021).…”

“…At both locations, the center station sensors experienced the least amount of tilt and some of the longest uninterrupted recording times. For details regarding the power density functions, tilt directions, rotations, and exact geometries at the Gulkana Glacier site see Marusiak et al (2020) and the northwest Greenland site (Marusiak, Schmerr, et al, 2021).…”

Seismic Detection of Euroquakes Originating From Europa's Silicate Interior

“…More sensitive equipment might be able to detect a M w 4.5 euroquake over a larger range of distances. Flight candidate seismometers under development, such as the Seismometer to Investigate Ice and Ocean Structure (Marusiak et al, 2020(Marusiak et al, , 2021, the Europa Seismic Package (Kedar et al, 2020), and the SSP (Nunn et al, 2021) may improve the chances of detecting a deep euroquake.…”

“…An additional difficulty arises from the lander concept design, which places the seismometer in the lander vault to protect from Europa's harsh surface radiation. Terrestrial analog studies in icy ocean world locations (Marusiak et al, 2020(Marusiak et al, , 2021 and in martian settings (Panning et al, 2020) show that placing seismometers on lander decks can introduce coda and additional noise, although these effects are greatly reduced in the absence of wind. The additional noise from the lander resonant frequencies tends to occur at high frequencies (≥50 Hz) and depends on specifics of the lander design and placement of the seismometer (Marusiak et al, 2021).…”