Research
My research can be divided between a focus on planetary applications, mostly Mars and icy ocean worlds, and terrestrial applications, mostly cryosphere studies and induced seismicity.
Instrument Development
Past missions like InSight have shown how powerful single-station seismometers can be. Future missions like Dragonfly and Farside Seismic Suite (FSS) already plan on including seismometers as part of their payloads. At UA, we work with Silicon Audio to develop the next generation of seismic instrumentation that could explore the Moon, asteroids, icy ocean worlds, and more.
In 2024 LEMS was selected as an instrument for the Artemis III Deployment. UA will be supplying the seismic sensors and will be part of the science team.
Induced Seismicity Studies
At the USGS I work in the Earthquake Science Center. We are working with scientists at Lawerence Berkeley lab to study the seismicity near geothermal sites. By documenting and characterizing the seismicity, we can better understand how the geologic context near these sites and better asses any seismic risks posed by energy production. Preliminary results will be presented at AGU.
The potential seismicity of Europa's icy shell has been previously studied, but it is currently unknown if Europa's silicate interior can produce seismic events, and if so, would a seismometer be able to detect those events. Using PlanetProfile, Axisem, and Instaseis, I compared waveforms from events originating near the surface and from the deeper interior with models that have thick and thin ice shells. We show the minimum event size needed to overcome background noise from tidal cracking. We also compare signal strength to instrument capabilities (right) to determine what seismicity might be recorded. Preliminary results were presented at AGU2021, SSA 22, and AbSciCon 22. A paper has been published with Earth and Space Sciences.
Seismic Events in Europa's Interior
Methane Clathrates in Ocean Worlds
Methane Clathrates may exist in the interiors of several icy ocean worlds, such as Titan. Their properties, especially thermal conductivity, vary from those of pure water ices. The differences in thermal and physical properties can influence the thermal, physical, and seismic structure of the icy worlds. Using PlanetProfile, I explore how clathrates can alter the interior structure of Titan, and if the differences caused by the presence of clathrates, could be detectable through geophysical observations (e.g.) seismology. Preliminary results were presented at AGU in 2020 and at LPSC in 2021, and 2022. A paper has been published with the Planetary Science Journal.
Geophysical Exploration of Habitable Worlds
As we search for life in our solar system and beyond, geophysical approaches can help us investigate potentially habitable environments that may lurk kilometers beneath icy shells. In this lecture given to the Network for Ocean Worlds (NOW) I discuss the different technologies and instruments that will help us search for habitable conditions. The approaches are discussed in more detail in the Planetary Sciences Journal (Marusiak et al 2021).
Icy Ocean World Seismology
Europa and Enceladus are two icy moons that have subsurface oceans beneath their exterior icy shells. Because of the potential habitability of these oceans, NASA has made studying these moons a priority. Specific interests include determining the seismicity of the icy shells and the structure of the ice shells and oceans.
The Seismometer to Investigate Ice and Ocean Structure (SIIOS) team was funded through a NASA PSTAR grant to study the science capabilities of flight-ready instruments. We use Gulkana Glacier in Alaska, and a site in Northwest Greenland as analog sites to test the instruments. Our goals include 1) comparing the flight-ready instrument (Silicon Audio) to traditional instruments 2) compare ground-based instrumentation to deck-mounted instrumentation, 3) compare capabilities of a single-station to a small-aperture array.
My part of the project focuses on 1) using the active source experiment to determine the local structure of the ice 2) develop a location algorithm and test the uncertainty in location using the active source experiment and regional passive events 3) build a catalog of passive events to quantify a small-aperture array's ability to detect events. My portion of the work will also be partially funded by the NASA Earth and Space Science Fellowship (NESSF).
Preliminary results have been presented at several conferences including LPSC and AGU. A paper which describes the data collected at our Gulkana, Glacier field site has been published with SRL, a second paper focusing on the Greenland deployment has also been published in SRL.
Image Credit: JPL/NASA
Image Credit: NASA/Caltech/JPL
Mars and Deep Interiors
In 2018 NASA plans to send seismometers to Mars aboard the InSight (INterior Exploration using Seismic Investigations, Geodesy, and Heat Transport) mission. As part of mission preparations, I'm using terrestrial events to test the quantity and quality of events that would be required to constrain the depth to the Martian Core. I created 22 models based on the PREM model with core depths between 2791-2991km in increments of 10km. I randomly select terrestrial events and stack their amplitudes at each model's expected time of arrival. The difference between actual and predicted arrival times are also compared. Using this method, I'm able to test how many events are required to constrain the core depth. I have also tested how the quality of events affects core depth uncertainty. Location uncertainty was also added to quantify its affect on my algorithm. We further tested how ScS multiples could be used to increase the number of stacks in our analysis. Preliminary results can be viewed in the LPSC abstracts, (Marusiak et al., 2016) and (Marusiak et al., 2017). A paper with full results has been published in Icarus. Data from InSight has now been used to help constrain the size of the core. Preliminary results have been presented at LPSC and EGU in 2021, with a published paper in Science (Stähler et al 2021).