The Detection of Seismicity on Icy Ocean Worlds by Single-Station and
Small-Aperture Seismometer Arrays
Abstract
Future mission 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 the automated Short-Term Average/ Long-Term Average
technique. We find that with a 2-meter small-aperture seismic array, our
detection rate increased (9 % for Alaska, 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 high frequency 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 low-frequency
global tectonic events. Based upon this study, we recommend that future
missions consider the value of the expanded capability of a small array
compared to a single station, design detection algorithms that can
accommodate variable environmental noise, and assess the potential
landings sites for sources of local environmental noise that may limit
detection of global events.