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CWP Seminars - 2015 Fall

CWP seminars discuss topics pertaining to our broad areas of research interests. These seminars are led by CWP faculty, students and, on occasion, by guest presenters. CWP seminars are held every Monday at 4 p.m. in the Green Center on the Colorado School of Mines campus. Click here to see previous CWP Seminars.

Note: To view weekly seminar schedules of individual CWP teams, click a link below:

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Fall 2015 CWP seminars

Date Speaker(s) Title Abstract
9/7

Thomas Planès

Thomas Planès

CWP Visiting Scholar

Monitoring the tidal response of a sea levee with ambient seismic noise

Internal erosion, a major cause of failure of earthen dams and levees, is often difficult to detect at early stages using traditional visual inspection. The passive and non-invasive seismic interferometry technique could enable the detection of internal changes taking place within these structures. The technique is here tested on the Dutch sea levee of Colijnsplaat, which presents signs of concentrated seepage in the form of sandboils. Using passive ambient seismic data collected over a 12 hour period, surface waves propagating along the levee are reconstructed through seismic interferometry. Two dominant ambient seismic noise sources are identified, the traffic on the Zeeland bridge and a nearby wind turbine. Time lapse variations of the surface wave velocities are then computed during the 12 hour tidal cycle for different frequency bands, i.e. depth ranges. The velocity variations correlate with on site pore water pressure measurements. Some spatially localized relative velocity variations of up to 5% are observed.

1st CWP seminar of the Fall 2015 semester (CWP administrative topics)

8/31

Antoine Guitton

Antoine Guitton

Stanford University

Full or not-so-full waveform inversion?

In the past few years, the number of Full Waveform Inversion (FWI) applications and results has increased dramatically with the premise that FWI can yield high resolutions models. However, given the number of approximations that are being made by practitioners to make FWI feasible, are high resolution models a wishful thinking or a tangible goal to attain? It is my observation that the best FWI results with the most impact on imaging are usually coming from the inversion of medium/long wavelengths of the model, inverting mostly long offsets, post-critical events or diving waves. Results showing a high degree of details in the velocity model, one of the selling points of FWI, are often questionable. For an acoustic medium parameterized with both Vp and density, this talk will review basic principles of FWI and one of its pitfalls: the inherent ambiguity between Vp and density, especially at short offsets. The importance of "parameterization" will also be discussed.

1st CWP seminar of the Fall 2015 semester (CWP administrative topics)

 

Previous CWP Seminars

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