InSight is a proposed Discovery mission which will deliver a lander containing geophysical instrumentation, including a heat flow probe and a seismometer package, to Mars. The aim of this mission is to perform, for the first time, an in-situ investigation of the interior of a truly Earth- like planet other than our own, with the goal of understanding the formation and evolution of terrestrial planets through investigation of the interior structure and processes of Mars

Banerdt, W. Bruce

Beucler, Eric

Boschi, Lapo

Johnson, Catherine

Lognonne, Philippe

Mocquet, Antoine

Panning, Mark P.

Weber, Renee C.

NASA Technical Reports Server

InSight: Single station broadband seismology for probing Mars’ interior. Mark
P. Panning1, W. Bruce Banerdt2, Eric Beucler3, Lapo Boschi4, Catherine Johnson5, Philippe Lognonne6, Antoine
Mocquet3, Rene´e C. Weber7, 1Dept. of Geological Sciences, University of Florida, (mpanning@ufl.edu), 2Jet Propul-
sion Laboratory, 3Laboratoire de Plane´tologie et Ge´odynamique, Universite´ de Nantes, 4Institute of Geophysics, ETH
Zurich, 5Dept. of Earth and Ocean Sciences, University of British Columbia, 6Institut de Physique du Globe Paris,
7NASA Marshall Space Flight Center
Introduction: InSight is a proposed Discovery mis-
sion which will deliver a lander containing geophysical
instrumentation, including a heat flow probe and a seis-
mometer package, to Mars. The aim of this mission is to
perform, for the first time, an in-situ investigation of the
interior of a truly Earth- like planet other than our own,
with the goal of understanding the formation and evo-
lution of terrestrial planets through investigation of the
interior structure and processes of Mars.
SEIS Instrumentation: One of the critical instrumen-
tation components for the InSight mission will be the
Seismic Experiment for Interior Structure (SEIS) [1].
SEIS comprises two sensor assemblies mounted on a lev-
eling mechanism which will be deployed on the surface:
a 3- axis very broad band (VBB) oblique seismometer
within an evacuated sphere, and an independent 3-axis
short period (SP) seismometer outside. The combina-
tion of the two sensor assemblies allows for high pre-
cision measurements over a very broad frequency band
(<10−9m/s2/Hz1/2 between 0.001 and 1 Hz for VBB
and <5×10−9m/s2/Hz1/2 between 0.01 and 50 Hz for
SP).
Such instrumentation will allow for an unprece-
dented view of the interior of Mars. However, since the
proposed mission will have only a single lander and no
network, we will not be able to apply traditional source
location methods and will need to take advantage of sin-
gle station approaches.
Expected sources of energy: A first-order scientific
return of such a mission will be information on the seis-
mic activity of the planet. We can, however, use esti-
mates of Martian seismicity based on thermal calcula-
tions [2] or extrapolation of historical faulting [3, 4] to
estimate data availability. Based on these estimates and
the capabilities of the SEIS instrumentation, we antici-
pate being able to record body wave information for be-
tween 30 and 40 quakes of seismic moment greater than
or equal to 1013Nm during 2 years. Of these, we antic-
ipate on the order of 4 to 5 events with seismic moment
greater than or equal to 1016Nm (∼MW 4.7), which will
be large enough to allow for recording of at least 3 orbits
of Rayleigh waves.
Multiple orbit surface wave data: When a single
seismic station is available, the record of the successive
surface wave trains generated by an event can be used to
assess the spherically averaged phase and group veloc-
ities as a function of frequency, the epicentral distance,
and the origin time of the event. On the Earth, the deter-
mination of seismic velocities along the great circle paths
is a standard procedure, initiated in the 1950’s and 1960’s
[5, 6], that has been widely used for several decades [e.g.
7, 8], and can be applied without any knowledge of the
source location and origin time or correction for instru-
mental response. Using the R1, R2, and R3 notation for
the successive minor and major arc wavetrains, and the
signal-to-noise ratio expected for SEIS, R1 wavetrains
generated by a Mw 4.7 event can be observed on the
Earth at 5000 km epicentral distance in the 35-50 s pe-
riod range, but R2 and R3 wavetrains are below the noise
level (fig. 1). This is mainly due to the large associated
travel distances (35 000 km and 45 000 km), respectively,
and to the damping effect of the oceans. On Mars, the
smaller planetary radius (about half of the Earth’s) and
the absence of oceans, result in a much weaker atten-
uation of the dispersed wavetrains in this period range.
This should enable the SEIS seismometer to observe
R2 and R3 wavetrains at all distances for marsquakes
with moment magnitude greater than 4.7 (fig. 1). Con-
sidering a very conservative 20 s error on arrival time
determinations, the precisions expected on great-circle
surface-wave velocities and epicentral distances are ex-
pected within the ranges 1% and 200 km, respectively.
For these events where we are able to estimate epi-
central distance from surface wave arrival times, we can
make arrival time picks for body wave phases as well,
allowing for the estimation of P and S travel time curves.
If enough picks are available to fit a smooth curve to the
travel time picks, we can use classical seismology tech-
niques such as Herglotz-Wiechert inversion [e.g. 9, ch. 9]
to create a smoothed velocity profile for the mantle. Even
if the picks are too sparse for such an analytic approach,
a few differential S-P times can be used in connection
with the constraints from the Rayleigh wave dispersion
characteristics to constrain simple mantle velocity mod-
els. With the mantle velocity constraints, any reflected
phases observed in these events, such as PcP or ScS can
then be used to constrain the core radius.
https://ntrs.nasa.gov/search.jsp?R=20120013652 2019-08-30T21:51:38+00:00Z
2Figure 1: Amplitude of Rayleigh wave trains normalized by R1 amplitude at an epicentral distance of 90◦ on Earth
(10,000 km). S/N numbers on y-axis are forMW 4, but seismic moment labels in center of figure indicate the minimum
amplitude that is required to observe a particular wave train with a S/N ratio of 1.
Other single-station approaches: For events where
we may be able to observe some body wave or surface
wave energy but not multiple orbits to estimate epicen-
tral distance, we can still apply well-developed single-
station approaches to constrain structure of the crust and
upper mantle. In particular, the method of receiver func-
tions, which only requires three component recordings
of incoming P or S waves and no source information has
been in use for decades [10] and has been applied to lunar
data [11], should be able to constrain crustal thickness
as well as possibly identifying upper mantle discontinu-
ities. Further constraints on upper mantle structure may
be possible from other approaches such as the analysis of
the ellipticity of surface waveforms [12].
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InSight: Single Station Broadband Seismology for Probing Mars' Interior

InSight: Single Station Broadband Seismology for Probing Mars' Interior

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