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

Abstract

Future missions carrying seismometer payloads to icy ocean worlds will measure global and local seismicity to determine where the ice shell is seismically active. We use two locations, a seismically active site on Gulkana Glacier, Alaska, and a more seismically quiet site on the northwestern Greenland Ice Sheet as geophysical analogs. We compare the performance of a single‐station seismometer against a small‐aperture seismic array to detect both high (>1 Hz) and low (<0.1 Hz) frequency events at each site. We created catalogs of high frequency (HF) and low frequency (LF) seismicity at each location using an automated short‐term average/long‐term average technique. We find that with a 1‐m small‐aperture seismic array, our detection rate increased (9% for Alaska and 46% for Greenland) over the single‐station approach. At Gulkana, we recorded an order of magnitude greater HF events than the Greenland site. We ascribe the HF events sources to a combination of icequakes, rockfalls, and ice‐water interactions, while very HF events are determined to result from bamboo poles that were used to secure gear. We further find that local environmental noise reduces the ability to detect LF global tectonic events. Based upon this study, we recommend that (a) future missions consider the value of the expanded capability of a small array compared to a single station, (b) design detection algorithms that can accommodate variable environmental noise, and (c) assess the potential landings sites for sources of local environmental noise that may limit detection of global events.

Salt Distribution from Freezing Intrusions in Ice Shells on Ocean Worlds: Application to Europa

“…This might lead to a difference in tidal displacement or fracturing detectable by imaging or altimetry (e.g., Steinbrügge et al 2015). Second, subsurface intrusions or the frozen remains of former intrusions, and some of their characteristics (e.g., shape) could be detectable by radar sounding (e.g., Schroeder et al 2016), gravimetry (Ermakov et al 2017;Park et al 2020;Raymond et al 2020), or from the surface using electromagnetic sounding (Grimm et al 2021;Biersteker et al 2023) or seismometry (Vance et al 2018;Marusiak et al 2022). Third, indirectly, an intrusion could be detected by how the spatial variations that it induces in thermal diffusivity changes the local thickness of the icy lithosphere and full ice shell.…”

Seismology in the Solar System

“…The observability of seismic waves from quakes in the silicate mantle would highly depend on their magnitude, but would be made less likely by the presence of soft layers on the seafloor or the ice bottom (Marusiak, Panning, Vance, Nunn, et al 2021). In general, operation of a warm lander on ice will pose challenges to coupling of seismic sensors due to melting and tilting (Marusiak, Schmerr, et al 2022).…”