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Review of the Seismicity of Mars

Description: 

The InSight mission collected an astounding seismic dataset from Mars during more than four years (1450 sols) of operation until it was retired on 21 December 2022. The Marsquake Service detected more than 1300 events of seismic origin. The largest marsquake (S1222a, M=4.6) was recorded recently on May 4, 2022. Two other significant events (S1000a and S1094b) have been confirmed as distant impacts, with magnitudes of M4.0 and 4.2 and crater diameters of 130 and 150 m respectively. Here, we present the current understanding of the Martian seismicity and the different types of events we have observed on Mars.

The Low Frequency (LF) family of events include energy predominantly below 1 Hz. They are similar to teleseismic events on Earth, with clear P and S waves. The epicenter is known for about half of the LF events, owing to the difficulty of determining back-azimuth. Seismicity occurs at only a few spots around Mars and no tectonic events were located within 25° of InSight. A large number of LF events are located 26–30° from the station, associated with the volcanic Cerberus Fossae region. Two events lie beyond the core shadow and have PP and SS phases - S0976a in the Valles Marineris region 146° away from InSight, and the S1000a impact. LF events have the largest magnitudes. The High-frequency (HF) family of events exhibit energy predominantly at and above the 2.4 Hz local subsurface resonance. HF events generally have magnitudes below M2.5 and originate from a distance range of 25–30°, from a region around the central Cerberus Fossae. Likely these are shallow events associated with volcanic dykes. HF events have a clear seasonal trend that is not yet understood. A small number of HF events are characterized by higher frequency content, up to 20–30 Hz with a notable amplification on the horizontal components at very high frequency, and are termed Very High Frequency (VF) events. The amplification is plausibly explained by the local subsurface structure. These events are observed only close to the lander. The closest VF events include a distinctive acoustic signal, and remote imaging confirms they are impacts.

Session: Earthquake Source Parameters: Theory, Observations and Interpretations

Type: Oral

Date: 4/18/2023

Presentation Time: 02:00 PM (local time)

Presenting Author: John Clinton

Student Presenter: No

Invited Presentation: Yes

Authors