An update on the Seismicity of Mars as Recorded by InSight's Marsquake Service

Kurzfassung

Over 3 Earth years since the InSight lander arrived on Mars and despite growing power challenges, the seismic data collection from the SEIS seismometer package is now well into a 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 over 1250 distant marsquakes and a similar num- ber of 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 there is remarkably similarity between 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 readily identified and used to determine distances and magnitudes. However, polarised energy is rarely observed in marsquakes, so estimates of back azimuths, and hence also event locations, are limited to only 10 events so far. Here, we review the seismicity seen so far on Mars, in terms of location, magnitude, magnitude-frequency distribution, tectonic context and possible seismic sources. We highlight the similarity of marsquake rates seen between the 2 martian years. We focus on characteristics of significant recent high amplitude high quality events that locate both close to the lander as well as on the other hemisphere.