Seismicity of Mars

Abstract

Abstract. Determining of focal mechanism mechanism and seismic moment tensor (MT) are he most difficult problems in seismology. We propose the method that enables to obtain the focal mechanism solution by inversion of waveforms for the Marsquakes which was recorded by the Very Broad Band sensors and associated channel ELYSE and is located 37.2° away from InSight. Seismic data recorded by the SEIS experiment [7], [8] onboard the InSight mission [1] have shown that Mars is seismically active with more than 1300 events detected and catalogued by the InSight Marsquake Service (MQS) [5], [4], [3]. The global seismic event rate sets Mars as moderately active, between the weak lunar activity and the terrestrial intraplate seismicity [1] and provided enough seismic records to perform the first structure inversions of the planet. See [9] for a review of results. But on May 4th, 2022, NASA’s InSight Mars lander has detected the largest quake ever observed on another planet: an estimated magnitude Mw4.7 temblor that occurred the 1,222nd martian day, or sol, of the mission [6]. We used a point-source approximation, assuming the location and origin time are known. We also used method based on a point source approach for an elastic, horizontally-layered medium to retrieve source parameters of events on Mars. The seismic moment tensor was calculated using the matrix method for only the direct P- and S waves. So, we propose to invert only the direct waves instead of the full field. This method is less sensitive to path effects than reflected and transformed waves. Our method enables obtaining a focal mechanism solution by inversion of waveforms recorded at only one station.