Low Frequency Marsquakes and Where to Find Them: Back Azimuth Determination Using a Polarization Analysis Approach

TL;DR

This paper introduces a polarization analysis method to determine the back azimuth of marsquakes using seismic data from NASA's InSight mission, enabling better localization of seismic events on Mars with a single station.

Contribution

The study develops and calibrates a polarization-based approach for back azimuth estimation, improving marsquake localization where traditional methods lack data.

Findings

Reliable back azimuths estimated for 24 marsquakes

16 of these azimuths were previously unavailable from MQS

Most events located east of InSight near Cerberus Fossae

Abstract

NASA's InSight mission on Mars continues to record seismic data over 3 years after landing, and to date, over a thousand marsquakes have been identified. With only a single seismic station, the determination of the epicentral location is far more challenging than on Earth. The Marsquake Service (MQS) produces seismicity catalogues from data collected by InSight and provides distance and back azimuth estimates when these can be reliably determined - when both are available these are combined to provide a location. Currently, MQS do not assign a back azimuth to the vast majority of marsquakes. In this work we develop and apply a polarization analysis method to determine the back azimuth of seismic events from the polarization of observed P and S-wave arrivals. The method is first applied to synthetic marsquakes, and then calibrated using a set of well-located earthquakes that have been recorded in Tennant Creek, Australia. We find that the back azimuth is estimated reliably using our polarization method. The same approach is then used for a set of high quality marsquakes recorded up to October 2021. We are able to estimate back azimuths for 24 marsquakes, 16 of these without MQS back azimuths. We locate most events to the east of InSight, in the general region of Cerberus Fossae.