Projects

HoloLens Visualizations

The Fossett Laboratory for Virtual Earth and Planetary Exploration at Washington University in St. Louis is actively exploring possibilities for the use of augmented reality (AR) platforms for use in Earth science learning.

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The ability to bring classic, well researched outcrops into the classroom and viewed in 3D at 1:1 scale provides an instructor to take students to where geologic discoveries were made. The technology can also be used for field trip preparation or review, allowing accurate measurements to be taken using georeferenced photogrammetric models.

We are developing applications for the Microsoft HoloLens, an untethered AR headset that allows the display of 3D holograms from online sources, as well as shared experiences between a number of headsets. GeoXplorer is available for free on the Microsoft Store for HoloLens.

View Gothic Cavern AR

Augmented Reality Ice Sheet

Click on the image below to try out a WebGL prototype:

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Whillans Ice Stream Seismology

The Whillans Ice Stream located along the Siple Coast, channels ice from the West Antarctic Ice Sheet out on to the Ross Ice Shelf. At its end the topography flattens into a 100x100km ice plain that exhibits curious seismic properties. The plain, as a whole, undergoes twice-daily, stick-slip motion where it lurches forward 0.5m in ~30mins and then remains stationary for the rest of the slip cycle.

Seismic instruments, coupled with GPS stations have provided a way to characterize these slip events, uncovering the pattern of rupture. Three separate sticky-spots allow for the acceleration of rupture, and match up with 3 distinct surface wave arrivals observed  over 1000km away (Pratt et al., 2014).

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Noise sources within the Southern Ocean (and as far away as southern Greenland) have also been detected with this circular array of seismometers. The array is able to detect the location of storms based on the slowness and backazimuth of coherent energy within the noise field. Frequencies are also highly affected by the seasonal sea ice that switches off the primary (or single-frequency) and short-period secondary (or double-frequency) microseisms. Only the long-period secondary microseism remains strong year-round (Pratt et al., 2017).

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Finally, we have been using the ambient noise cross-correlations to tease out Rayleigh waves that reflect the shallow Earth structure between each station of the array. At the shortest periods (~4-6s) the Rayleigh wave ellipticity is sensitive to sediment thickness just beneath the bed of the ice stream. Our results show a somewhat abrupt thickening of sediments across a structure that is sub-parallel to the Trans-Antarctic Mountains (which is a paleo-rift flank) and interpret this thickening as a normal fault. The use of this technique on a small, temporary array may help improve our understanding of the characteristics of ice sheet beds.

interpretations

Madagascar Crust and Upper Mantle Structure

Madagascar remained a large gap in passive broadband seismic exploration until October 2011 when the 25-station MACOMO network was deployed across the island. Prior to this network, and the contemporaneous networks of RHUM-RUM and SELASOMA, even the thickness of the continental crust was unknown. Furthermore, intraplate volcanism has been found in the north, central, and one outcrop in the south of the island dated to within the last 1 million years. One of the primary objectives of this project was to understand the crust and upper mantle structure to see if there was connection between these volcanic provinces and the known hotspot locations of Réunion and Comoros.

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So far two papers have been released on data collected from this project: Pratt et al. 2017 and Andriampenomanana et al. 2017, both looking at the crust and upper mantle using surface waves and receiver functions respectively. Low seismic velocity regions are found beneath all three recent volcanic provinces, the smallest province, in the south, appears to be somewhat detached from the crust. Connections to surrounding hotspots are uncertain due to the limited coverage between Madagascar and the Îles Éparses, however there may well be a link between the northern Madagascan volcanic province and the Comoros hotspot at >150km depth. Crustal thicknesses are ~40km for the backbone of the island, though elevations are high >2000m in places. Asthenospheric support beneath the crust in absence of continental lithosphere is hypothesized to account for this elevation, however the mechanism that would allow for this upwelling is still debated.

Vsv model (ascii .txt lat,lon,dep,Vsv)

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