Speaker:

Suzan van der Lee - Sarah Rebecca Roland Professor, Department of Earth and Planetary Sciences, Northwestern University

Title:

Subterranean dynamics in Earth and Mars, inferred from big and small seismic data

Abstract:

Via expanded and densified networks of increasingly advanced sensors, seismology has become a science of big data over the past half century. Seismologists track hundreds of seismic waves per earthquake to locate their epicenters and infer their failure mechanisms. We model thousands of waveforms and combine tens of millions residual wave propagation times to virtually 3D-print the Earth's interior structure. Sophisticated big-data analysis techniques extract subtle, though vital details about the Earth's crust from scattered waves and ambient, continuously recorded noise fields. This is in stark contrast to the data available for fellow terrestrial planets. The only other terrestrial planet we have seismic recordings from is Mars. Through 2019-2022 a single broadband seismometer was operational in Elysium Planitia on Mars, as part of the InSight mission, and recorded dozens of marsquakes with similar shear-dislocation failure mechanisms as earthquakes. However, estimating epicenters and failure mechanisms for these marsquakes with waveform data from merely a single seismometer presented a new challenge in our current data-driven century. This presentation will show how we adapted small-data analysis methods from the early days of digital seismology to be effective and robust analysis tools for Martian seismic data. Specifically we demonstrate how we estimate epicenters from relative arrival times of P and S waves and how we estimate failure mechanisms in terms of fault orientation and slip direction from relative amplitudes of P and S waves. We will discuss the implications of our findings in terms of potential geologic, tectonic, and volcanic activity on Mars, a planet much smaller, colder and quieter than Earth. We conclude with a discussion on how we use algebraic geometry to improve uncertainty estimates for our inferences.

Speaker Bio:

Suzan van der Lee is the Sarah Rebecca Roland Professor in the Department of Earth and Planetary Sciences at Northwestern University. She is also a NICO Core Faculty member, and a lead Professor with the Metropolitan Chicago Data-science Corps (MCDC).

Earthquakes are powerful evidence that the Earth is continuously reshaping. The seismic signals emitted by earthquakes encrypt 1) important information about these powerful and sometimes destructive events, and 2) intelligence about the ongoing modification and dynamics of the Earth's interior. Professor van der Lee applies data science to extract this intelligence from millions of records of seismic waves. She is particularly interested in developing and applying new methods of inference to extract relevant signals from seismic records and to image the Earth’s interior structure from heterogeneous data. She is a practiced observational seismologist and co-develop seismic and joint tomography methods, including those using waveforms.

Location:

In person: Chambers Hall, 600 Foster Street, Lower Level
Remote option: https://northwestern.zoom.us/j/95501815086
Passcode: NICO23

About the Speaker Series:

Wednesdays@NICO is a vibrant weekly seminar series focusing broadly on the topics of complex systems and data science. It brings together attendees ranging from graduate students to senior faculty who span all of the schools across Northwestern, from applied math to sociology to biology and every discipline in-between. Please visit: https://bit.ly/WedatNICO for information on future speakers.

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