The seismicity of Mars, as catalogued by InSight&#8217;s Marsquake Service
Authors: Dahmen Nikolaj ,   InSight's Marsquake Service
Published: July 2021

NASA&#8217;s InSight lander continues to record high-quality seismic data from the surface of Mars two and a half years after landing [1,7,9]. The data collected by the SEIS seismometer package [8] are routinely monitored by the Marsquake Service (MQS) [4,5], a core mission service that is tasked with curating the Martian seismicity catalogue. To date, more than 500 distant marsquakes have been identified, which can be classified by their frequency content into high- and low- frequency event families [4,7,10]. In addition, the catalogue includes over 800 short-duration events potentially associated with local thermal cracking [6]. The local atmospheric conditions have a strong influence on the seismic noise level, which varies from levels below pre-mission expectation during the evening, to high-noise levels during the day owing to strong winds and atmospheric turbulence. Due to the low signal amplitude of the marsquakes, their detection is mainly restricted to evenings and nights with low to moderate winds. Following the marsquake detection and discrimination from atmospherically-induced energy, MQS identifies crustal and body phase arrivals and proposes a distance based on the travel time differences. Only a handful of low-frequency marsquakes have a clear polarized arrival that allows MQS to determine the backazimuth and hence provide an event location. Deep into the second Martian season of continuous seismic observation, we provide an update on the recent seismicity and the seasonally repeating features of the dataset. This includes an overview of MQS&#8217; procedures of monitoring the seismic dataset and the different marsquake types observed, as well as a review of event location, magnitude [2], moment tensors [3] and possible seismic sources.References:[1] Banerdt, W. Bruce, et al. "Initial results from the InSight mission on Mars." Nature Geoscience 13.3 (2020): 183-189.[2] B&#246;se, Maren, et al. "Magnitude Scales for Marsquakes Calibrated from InSight Data." Bulletin of the Seismological Society of America (2021).[3] Brinkman, Nienke, et al. "First focal mechanisms of marsquakes." Journal of Geophysical Research: Planets 126.4 (2021): e2020JE006546[4] Clinton, John, et al. "The Marsquake catalogue from InSight, sols 0&#8211;478." Physics of the Earth and Planetary Interiors 310 (2021): 106595.[5] Clinton, John, et al. "The Marsquake service: Securing daily analysis of SEIS data and building the Martian seismicity catalogue for InSight." Space Science Reviews 214.8 (2018): 1-33.[6] Dahmen, Nikolaj, et al. "Super high frequency events: a new class of events recorded by the InSight seismometers on Mars." Journal of Geophysical Research: Planets 126.2 (2021): e2020JE006599.[7] Giardini, Domenico, et al. "The seismicity of Mars." Nature Geoscience 13.3 (2020): 205-212.[8] Lognonn&#233;, Philippe, et al. "SEIS: Insight&#8217;s seismic experiment for internal structure of Mars." Space Science Reviews 215.1 (2019).[9] Lognonn&#233;, Philippe, et al. "Constraints on the shallow elastic and anelastic structure of Mars from InSight seismic data." Nature Geoscience 13.3 (2020): 213-220.[10] van Driel, Martin, et al. "High&#8208;Frequency Seismic Events on Mars Observed by InSight." Journal of Geophysical Research: Planets 126.2 (2021): e2020JE006670.