Simultaneous Determination of Structure and Event Location Using Body and Surface Wave Measurements at a Single Station: Preparation for Mars Data from the InSight Mission

Abstract:

An important challenge for the upcoming InSight mission to Mars, which will
deliver a broadband seismic station to Mars along with other geophysical
instruments in 2016, is to accurately determine event locations with the use
of a single station. Locations are critical for the primary objective of the
mission, determining the internal structure of Mars, as well as a secondary
objective of measuring the activity of distribution of seismic events. As part
of the mission planning process, a variety of techniques have been explored for
location of marsquakes and inversion of structure, and preliminary procedures
and software are already under development as part of the InSight Mars Quake
and Mars Structure Services. One proposed method, involving the use of
recordings of multiple-orbit surface waves, has already been tested with
synthetic data and Earth recordings. This method has the strength of not
requiring an a priori velocity model of Mars for quake location, but will only
be practical for larger events. For smaller events where only first orbit
surface waves and body waves are observable, other methods are required. In
this study, we implement a transdimensional Bayesian inversion approach to
simultaneously invert for basic velocity structure and location parameters
(epicentral distance and origin time) using only measurements of body wave
arrival times and dispersion of first orbit surface waves. The method is
tested with synthetic data with expected Mars noise and Earth data for single
events and groups of events and evaluated for errors in both location and
structural determination, as well as tradeoffs between resolvable parameters
and the effect of 3D crustal variations.