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Seismometer Detection of Dust Devil Vortices by Ground Tilt

Abstract : We report seismic signals on a desert playa caused by convective vortices and dust devils. The long-period (10-100 s) signatures, with tilts of similar to 10(-7) radians, are correlated with the presence of vortices, detected with nearby sensors as sharp temporary pressure drops (0.2-1 mbar) and solar obscuration by dust. We show that the shape and amplitude of the signals, manifesting primarily as horizontal accelerations, can be modeled approximately with a simple quasi-static point-load model of the negative pressure field associated with the vortices acting on the ground as an elastic half-space. We suggest the load imposed by a dust devil of diameter D and core pressure Delta P-o is similar to(pi/2)Delta PoD2, or for a typical terrestrial dust devil of 5 m diameter and 2 mbar, about the weight of a small car. The tilt depends on the inverse square of distance and on the elastic properties of the ground, and the large signals we observe are in part due to the relatively soft playa sediment and the shallow installation of the instrument. Ground tilt may be a particularly sensitive means of detecting dust devils. The simple point-load model fails for large dust devils at short ranges, but more elaborate models incorporating the work of Sorrells (1971) may explain some of the more complex features in such cases, taking the vortex winds and ground velocity into account. We discuss some implications for the InSight mission to Mars.
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Submitted on : Monday, April 27, 2020 - 10:16:23 AM
Last modification on : Friday, June 12, 2020 - 5:38:06 PM

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Ralph Lorenz, Sharon Kedar, Naomi Murdoch, Philippe Lognonné, Taichi Kawamura, et al.. Seismometer Detection of Dust Devil Vortices by Ground Tilt. Bulletin of the Seismological Society of America, Seismological Society of America, 2015, 105 (6), pp.3015-3023. ⟨10.1785/0120150133⟩. ⟨insu-02555145⟩

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