Planetary Seismology using Single-Station and Small-Aperture Arrays: Implications for Mars and Ocean Worlds

Abstract

Studying geophysical station deployment on Earth is essential preparation for future geophysical experiments elsewhere in the solar system. Here, I investigated how single-station seismometers and small-aperture seismic arrays in analog settings can quantify instrument capabilities, develop methodologies to detect and locate seismicity, and constrain internal structure. First, I used a single-station seismometer in Germany to study how the NASA InSight mission could constrain core depth. I showed that InSight could recover the Martian core within ±30 km if ≥ 3 events are located within an epicentral distance uncertainty of < ±1 degree. Increasing the number of detected events reduces core depth uncertainty, and higher signal-to-noise events will not affect core depth uncertainty or recovery rate.

Next, I used environmental analogs in Earth's cryosphere to quantify how seismometer placement on a mock-lander would affect instrument performance and seismic science results for a future surface mission to an icy ocean world. If mock-lander instruments were unprotected from the wind, noise levels were 50 dB higher than those on the ground. However, once seismometers were shielded via burial, noise performances were similar to the ground-coupled seismometers, although spacecraft resonances were found at frequencies ~100 Hz. For icy ocean worlds lacking atmospheres, I showed that deck-mounted flight-candidate seismometers recorded ground motion comparably to surface-deployed instrumentation, with responses similar to terrestrial seismometers at frequencies > 0.1 Hz.

Finally, I investigated seismicity detection capabilities of single-station and small-aperture seismic arrays. Small-aperture arrays were more effective at distinguishing low-frequency seismic events from noise and had fewer false positive events than a single-station. The Greenland site detected a higher percentage of teleseismic and regional tectonic events while the Gulkana Glacier, Alaska site observed more high frequency events. The high frequency seismicity was interpreted as originating from moulins, drainage events, icequakes, and rockfalls. Both sites had very high frequency events (> 100 Hz) that came from poles left in the field. These studies inform landing site selection criteria, such that there were trades between detecting local seismicity at the expense of seeing more distant events, and detecting larger teleseismic events that inform on deeper internal structure.