The Seismicity of Mars as Recorded by InSight's Marsquake Service

Introduction: NASA’s InSight lander has been operating on the surface of Mars for over 1200 Martian solar days (sols). Despite decreasing power, the lander has acquired near continuous seismic data throughout the mission to date. The Marsquake Service (MQS) performs daily analysis of the data and catalogues the seismicity. The catalogue currently contains over 1300 local, regional and teleseismic marsquakes and more than 1300 events that are likely associated with thermal cracking close to the lander (Table 1). Here we will present the latest update on the marsquake catalogue.

Martian Seismic Data: The Martian seismic dataset is often heavily contaminated by atmospheric effects, especially during the daytime and in the Northern hemisphere autumn and winter (Figure 1)[1,2]. This environmental noise can obscure the seismicity which is often at low amplitudes. During spring and summer, the atmospheric conditions are much more favourable from shortly before sunset until approximately sunrise and much of the MQS catalogue is detected during these hours. Other transient effects on the data that can interfere with event detection are discussed in [3]. One notable feature of the seismic noise on Mars is a resonance at 2.4 Hz which is observed during quiet periods and is also excited by seismic events that contain energy at that frequency. This resonance is likely caused by sub-surface structure [4] and greatly enhances the detection rate of higher frequency events.

Figure 1: Daily spectrograms of VBB vertical component stacked from sol 72 to sol 1233 with catalogued marsquakes overlain. White lines are where data were not recorded. The black dotted line represents the equivalent sol in mission year 1 to sol 1233. The black dashed line marks 1 year since SEIS was fully deployed.

 

Marsquake Types and Qualities: MQS categorises marsquakes based on their frequency content and their location quality [2,5]. A full description of the categories and qualities can be found in [2], here we list the general characteristics:

Low Frequency (LF): All energy is below 2.4 Hz and most of the time below 1 Hz.

Broadband (BB): Energy is predominantly at low frequencies but can include energy at and above 2.4 Hz.

2.4 Hz: Energy is contained in a narrow frequency band around 2.4 Hz, reaching a maximum of 4 Hz. These events are thought to be low amplitude versions of High Frequency events.

High Frequency (HF): Energy is predominantly at 2.4 Hz but also extends above 4 Hz. There may also be energy at low frequencies but the dominant energy is at higher frequencies (as opposed to BB events).

Very High Frequency (VF): Energy is at high frequencies, sometimes reaching up to 30 Hz. Energy is strongest on the horizontal components, especially at higher frequencies.

Super High Frequency (SF): very short duration (~10s of seconds) events with mainly horizontal energy between 5-10 Hz. These events are highly temperature dependent and are likely due to thermal cracks observed in the near surface close to the lander [6].

For all except SF events a location quality is assigned based on the ability to identify phase picks and locate the event as follows:

Quality A: Multiple clear phases are identified, and clear polarisation can be defined. The source is well located with distance and backazimuth.

Quality B: Either the distance or the backazimuth is clear but not both. A full location cannot be provided. When clear phases are identified distance is calculated.

Quality C: Clear seismic signal is observed but phases are not readily assigned, nor polarisation identified. A distance may be assigned but will be uncertain.

Quality D: The signal has low signal to noise either due to a low amplitude signal or high contamination from environmental noise. No location is given and there is a small risk that the event may not be tectonic in origin.

The Marsquake Catalogue: The marsquake catalogue is released every three months with a three-month delay. The latest release is V10 [7]. The catalogue includes not only the type and quality of the events but also general information such as location, origin, magnitude and any secondary phases that have been picked. Table 1 shows the total seismicity catalogued up to sol 1233.

 

Table 1

Event Type	Total	A	B	C	D
LF	56	6	11	21	18
BB	37	6	10	16	5
2.4 Hz	988	0	49	353	586
HF	164	0	76	79	9
VF	69	0	25	33	11
SF	1383	0	0	323	1060

 

Noteworthy New Events: The V10 catalogue [7] and data release [8] contain some significant new events including 6 new Quality A events. Most notable is S1094b, BB, QA. This event, with M_w^Ma=4.0 is one of the largest BB events ever detected and originates in a region where no previous seismicity had been seen with a distance of ~60° and a backazimuth of 40°.

We will also introduce the largest event ever recorded on Mars, S1222a.

Summary: The InSight lander has provided an incredible seismic dataset and the MQS has meticulously catalogued the seismicity. Now well into its extended mission the seismicity from the second Martian year of operations has been exceptional and MQS will continue to add to the catalogue.

 

References: [1] Lognonné et al., 2020, Nature Geo., 13(3), 213-220. DOI: 10.1038/s41561-020-0536-y, [2] Clinton et al., 2021, Physics of the Earth and Planetary Interiors, 310, 106595, DOI: 10.1016/j.pepi.2020.106595, [3] Ceylan et al., 2021, Physics of the Earth and Planetary Interiors, 310, 106597, DOI: 10.1016/j.pepi.2020.106597, [4] Hobiger et al., 2021, Nature Comms, 12(1), 1-13, DOI: 10.1038/s41467-021-26957-7, [5] Giardini et al., 2020, Nature Geo., 13(3) 205-212, DOI: 10.1038/s41561-020-0539-8, [6] Dahmen et al., 2020, J. Geophys. Res., 126, p.e.2020JE006599, DOI: 10.1029/2020JE006599, [7] InSight Marsquake Service (2022), Mars Seismic Catalogue, InSight Mission; V10 2022-04-01, ETHZ, IPGP, JPL, ICL, Univ. Bristol,
https://doi.org/10.12686/a16, [8] InSight Mars SEIS Data Service, 2022, SEIS raw data, InSight Mission, IPGP, JPL, CNES, ETHZ, ICL, MPS, ISAE-Supaero, LPG, MFSC, DOI: 10.18715/SEIS.INSIGHT.XB_2016