Details

Autor(en) / Beteiligte

• Brinkman, N.
• Sollberger, D.
• Schmelzbach, C.
• Stähler, S. C.
• Robertsson, J.

Titel

Applications of Time‐Frequency Domain Polarization Filtering to InSight Seismic Data

Ist Teil von

• Earth and space science (Hoboken, N.J.), 2023-11, Vol.10 (11), p.n/a

Ort / Verlag

Hoboken: John Wiley & Sons, Inc

Erscheinungsjahr

2023

Link zum Volltext

Quelle

Wiley Online Library Journals

Beschreibungen/Notizen

• Abstract The seismometer Seismic Experiment for Interior Structure (SEIS) onboard the InSight lander was used to continuously record the seismicity on Mars from February 2019 to December 2022. To maximize the information that can be extracted from the seismic data, it is critical to identify and to suppress undesired features (e.g., environmental noise, scattered waves, seismic imprint of lander vibrations) and non‐seismic noise (e.g., instrument related artifacts). We present an advanced polarization filtering workflow in the time‐frequency domain to suppress undesired features and to enhance the signal‐to‐noise ratio of the SEIS recordings. We estimate time‐frequency‐dependent polarization attributes such as the ellipticity, directionality of the particle motion, and the degree of polarization to identify and filter out undesired data parts. After filtering in the time‐frequency domain, the seismic data are transformed back to the time domain, yielding broadband waveform data that can be used for further seismological analysis. We illustrate the benefits of our filtering approach with three use cases. Firstly, we show how polarization filtered data can help to constrain the source mechanism of the sol 1,222 event, the largest marsquake detected so far. Using the proposed polarization filtering techniques, we are able to enhance the S‐wave arrival by suppressing interfering randomly polarized scattered waves to successfully infer on the moment tensor of this event. Secondly, we show that polarization filters can be used to suppress instrument‐related glitches and, thirdly, to remove the seismic imprint left by the vibrating lander (mechanical resonances of the lander). Plain Language Summary The NASA InSight mission brought a seismometer to the surface of Mars that continuously monitored ground vibrations at the landing site. The goal was to record vibrations caused by marsquakes. Since seismic waves from marsquakes travel through the planet, such recordings contain information that allows scientists to image the interior structure of Mars. The signals from most of the quakes recorded by InSight are faint due to their low magnitudes and the large epicentral distance. Additionally, the recordings are contaminated by noise from local winds and the harsh temperature conditions on Mars lead to sudden stress relaxations inside the seismometer that are visible as distinct pulses (so‐called glitches) in the data stream. To accurately image the interior structure of the planet, it is of crucial importance to distinguish and separate such local, distorting signals from signals that originate from deeper parts of the planet. To do so, we make use of a method called polarization filtering, which is based on the analysis of the motion of the seismometer in three‐dimensional space as a function of time and frequency. We show that this motion is distinct for environmental noise, glitches, and marsquake signals and exploit it to clean the data from local disturbances. Key Points InSight's Seismic Experiment for Interior Structure (SEIS) data are contaminated by various types of seismic and non‐seismic noise components Time‐frequency domain polarization filtering allows one to automatically identify and suppress undesired noise components Polarization‐filtered waveform data enable a more stable moment tensor inversion and facilitate the interpretation of SEIS data