Abstract
The InSight (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) mission began collecting high quality seismic data on Mars in February 2019. This manuscript documents the seismicity observed by SEIS, InSight's seismometer, from this time until the end of March 2020. Within the InSight project, the Marsquake Service (MQS) is responsible for prompt review of all seismic data collected by InSight, detection of events that are likely to be of seismic origin, and curation and release of seismic catalogues. In the first year of data collection, MQS have identified 465 seismic events that we interpret to be from regional and teleseismic marsquakes. Seismic events are grouped into 2 different event families: the low frequency family is dominated by energy at long period below 1 s, and the high frequency family primarily include energy at and above 2.4 Hz. Event magnitudes, from Mars-specific scales, range from 1.3 to 3.7. A third class of events with very short duration but high frequency bursts have been observed 712 times. These are likely associated with a local source driven by thermal stresses. This paper describes the data collected so far in the mission and the procedures under which MQS operates; summarises the content of the current MQS seismic catalogue; and presents the key features of the events we have observed so far, using the largest events as examples.
Highlights
The InSight mission to Mars expects to use seismology to elucidate the structure and formation of the red planet (Banerdt et al, 2020)
SEIS was placed on the ground on Sol 25, and full protection was achieved on Sol 70 after the Wind and Thermal Shield (WTS) was placed over it
There were very significant reductions in noise observed during the deployment phase. This period spans data collected first from the SP sensor, when it was initially turned on days after landing while SEIS was still placed on the deck (Panning et al, 2020), to that observed by the VBB following the deployment on the Martian surface about 1 m away from the lander, through the comple tion of various efforts to reduce stresses induced from the tether that connects SEIS to the lander, and placement of the WTS over SEIS (Ceylan et al, 2020)
Summary
The InSight mission to Mars expects to use seismology to elucidate the structure and formation of the red planet (Banerdt et al, 2020). No high frequency events have azimuthally polarised arrivals, but there are often 2 clear energy packages interpreted as Pg and Sg (van Driel et al, 2020) Another class of seismic signals have been observed that are of much shorter duration and restricted to frequencies above 5 Hz. Over 700 of these have occurred since Sol 182, when continuous data began to be collected at higher sampling rates. The expected continuous data rate for 3-compo nent VBB data was 2 sps, with a combined vertical component at 10 sps created by on-board combining of the raw VBB and SP components (higher sampling rates up to 100 Hz were available only for short event requests), the body wave and local magnitude scales were derived at longer periods than used on Earth.
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