Detection, analysis and removal of glitches from InSight's seismic data
from Mars
Abstract
The instrument package SEIS (Seismic Experiment for Internal Structure)
with the three very broadband and three short-period seismic sensors is
installed on the surface on Mars as part of NASA’s InSight Discovery
mission. When compared to terrestrial installations, SEIS is deployed in
a very harsh wind and temperature environment that leads to inevitable
degradation of the quality of the recorded data. One ubiquitous artifact
in the raw data is an abundance of transient one-sided pulses often
accompanied by high-frequency spikes. These pulses, which we term
“glitches”, can be modeled as the response of the instrument to a step
in acceleration, while the spikes can be modeled as the response to a
simultaneous step in displacement. We attribute the glitches primarily
to SEIS-internal stress relaxations caused by the large temperature
variations to which the instrument is exposed during a Martian day. Only
a small fraction of glitches correspond to a motion of the SEIS package
as a whole caused by minuscule tilts of either the instrument or the
ground. In this study, we focus on the analysis of the glitch+spike
phenomenon and present how these signals can be automatically detected
and removed from SEIS’ raw data. As glitches affect many standard
seismological analysis methods such as receiver functions, spectral
decomposition and source inversions, we anticipate that studies of the
Martian seismicity as well as studies of Mars’ internal structure should
benefit from deglitched seismic data.