IAG-IASPEI 2017

講演情報

Oral

IASPEI Symposia » S19. Planetary seismology

[S19-4] Science goals and modeling of the Insight/SEIS experiment

2017年8月1日(火) 10:30 〜 12:00 Room 402 (Kobe International Conference Center 4F, Room 402)

Chairs: Philippe Lognonné (Institut de Physique du Globe de Paris-Sorbonne Paris Cité) , Bruce Banerdt (Jet Propulsion Laboratory)

11:15 〜 11:30

[S19-4-04] Modeling the seismic signals generated by dust devils on Mars

Balthasar Kenda1, 2, Philippe Lognonne1, Aymeric Spiga3, Taichi Kawamura4, Sharon Kedar2, Bruce Banerdt2, Ralph Lorenz5, Don Banfield6, Matt Golombek2 (1.Institut de Physique du Globe de Paris, Paris, France, 2.Jet Propulsion Laboratory, California Institute of Technology, Pasadena, USA, 3.Universite Pierre et Marie Curie, Paris, France, 4.National Astronomical Observatory of Japan, Japan, 5.Johns Hopkins University Applied Physics Laboratory, Laurel, USA, 6.Cornell University, Ithaca, USA)

The 2018 InSight mission to Mars will deploy the Seismic Experiment for Interior Structure (SEIS) at the surface of the red planet. In addition to the signals generated by quakes and meteor impacts, the SEIS seismometers will continuously measure the excitation produced by the atmosphere. Among the signals of meteorological origin, dust devils and convective vortices are of special interest since they are localized, frequent and ubiquitous on Mars and they have a characteristic seismic signature.
We modeled the long-period (T > 10 s) signals of dust devils based on Large-Eddy Simulations of the daytime atmospheric dynamics at the InSight landing site and on the quasi-static response of the ground to pressure loading. Results show that vortices with typical pressure drops of 1-3 Pa can generate tilt effects of 5-20 nm/s^2 over the weak regolith. These are well above the detection threshold, and the influence area extends to a few hundreds of meters away from the vortex core. The catalog of episodes in the simulation is used to estimate the detection rate at a single station, which is expected to be as high as one episode per Martian day. Different subsurface models were considered and the possibility of using pressure and seismic data to determine the compliance of the Martian regolith is discussed. In an analog terrestrial field study, dust devils also produced infrasounds and higher-frequency seismic waves interpreted as shallow surface waves propagating in the subsurface. These additional signals contribute to better locate the vortex and to estimate the seismic velocities of the Martian subsurface down to a few tens of meter depth.