Mapping the Seismicity of Mars With InSight

The InSight seismometers have recorded more than 1,300 events. Ninety-eight of these, named the low-frequency (LF) family, show energy predominantly below 1 Hz down to similar to 0.1 Hz. The Marsquake Service identified seismic phases and computed distances for 42 of these marsquakes, 24 of which have backazimuths. Hence, the locations of the majority of LF family events remain undetermined. Here, we use an envelope shape similarity approach to determine event classes and distances, and introduce an alternative method to estimate the backazimuth. In our analysis, we use the highest quality marsquakes with known distances as templates, including the largest event S1222a, and assign new distances to similar group of events for which distance estimates were not previously available. We find the Tharsis region to be more active than initially perceived on the basis of 5 newly located events near Valles Marineris and Olympus Mons. We relocate two marsquakes with little or no S-wave energy in the NE of the Elysium Bulge. The event epicenters in Cerberus Fossae follow a north-south trend due to uncertainties in location, while the fault system is in the NW-SE direction; therefore, these events are re-projected along the observed fault system based on our interpretations. The marsquakes in our interpreted catalog are predominantly observed in the northern hemisphere of Mars above the equatorial dichotomy boundary. Plain Language Summary InSight's seismometer recorded more than 1,300 events since landing on the surface of Mars in November 2018 until it retired in December 2022. Most of the events InSight recorded are at high frequencies >= 2.4 Hz. The rest of the events, named the low-frequency family, produce signals that travel through the planet's interior, allowing us to understand the interior structure when event locations can be determined. In order to use the single-station approaches for computing the distance and the angle between the station and an event, at least two clear seismic phase arrivals (such as P- and S-waves for distance and P-wave for event angle) are required. However, marsquakes are often weak and do not always exhibit clear seismic phases; therefore, they cannot be assigned distances using traditional techniques. Here, we use the well-understood, highest-quality events as templates to investigate and assign a source region to the weaker seismic signals. Seismicity on Mars occurs mostly along or north of the boundary between the southern highlands and northern lowlands. Valles Marineris is seismically more active than previous catalogs of located events imply. Further, we show evidence that two events likely originate from the Olympus Mons region.