The Seismicity on Mars as recorded by InSight's Marsquake Service

Kurzfassung

Over 2.5 Earth years since the InSight lander arrived on Mars and despite growing power challenges, the continuous seismic data collection from the SEIS seismometer package is now well into the second martian year, and SEIS continues to exceed performance expectations in terms of the observed minimum noise. The Marsquake Service is tasked with creating and curating the seismicity catalogue for Mars. To date, nearly 800 distant marsquakes, and almost 1000 events likely associated with near-source thermal cracking, have been identified. The background noise recorded by SEIS is strongly sensitive to local winds, whose strength and duration is changing across the martian year, though is remarkable similar across martian years. Marsquake signal amplitudes remain small and marsquakes can generally only be detected during the quietest periods that mostly occur during the evenings. For many regional marsquakes, crustal or mantle body phase arrivals are identified and used to determine distances. However, polarised energy is rarely observed in marsquakes, so estimates of back azimuths, and hence also event locations, are limited to a handful of events. Here we summarise the content and the features of the marsquake catalogue recorded so far, with a focus on new methodologies and procedures adopted by the Marsquake Service. Further, we review the seismicity on Mars, including location, magnitude, magnitude-frequency distribution, tectonic context and possible seismic sources. In particular, we highlight the similarity of marsquake rates seen between the martian years.