Examining the P-wave coda features of InSight seismic events

The seismic events from the NASA InSight mission have provided a groundbreaking opportunity to explore the internal structure of Mars, from its crust to core. Events are catalogued by the MarsQuake Service (MQS) into several classes based on their frequency content and signal to noise ratio. This classification has provided a useful framework in which to decode Martian seismicity. In this work we will highlight newly observed features in the P-wave coda of these events to add to this effort.

A prominent feature of event waveforms on Mars is scattering, particularly at high frequencies (above 1 Hz) where the dominant energy of the majority of events is visible. The scattering obfuscates signal polarization, making seismic phase identifications and back azimuth estimations difficult. Although several events have been linked to particular sources, including impacts and tectonic features, the origin of a large number of events remains poorly constrained. Nevertheless, the scattering behaviour within events has offered important clues to the interior structure of Mars and its variation. Here, we present a re-analysis of Martian event envelopes to identify arrival features in the P-wave coda and how these vary across event types and epicentral distances. Using this additional information, we can further constrain MQS distance estimates and subsequently infer the implications for Mars’ internal structure and event origins. This helps open the door to new avenues for processing marsquakes to help place constraints on the seismicity of Mars.