Joint inversion of disparate geophysical observations for 3D geophysical modelling

Event Details
  • Date/Time:
    • Thursday August 31, 2017
      10:55 am - 11:40 am
  • Location: Ford Environmental Science & Technology Bldg, Rm. 1205
  • Phone: 4048941757
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Summary Sentence: Joint inversion of disparate geophysical observations for 3D geophysical modelling

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  • Dr. Monica Maceira Dr. Monica Maceira

EAS Fall Seminar Series

Dr. Monica Maceira, University of Tennessee Knoxville

When an earthquake or underground explosion occurs, the seismic waves that are generated propagate through the earth, reflecting and refracting at different interfaces and illuminating its 3D structure, while also carrying the signature of the source. The wavefield recorded for many events at many stations around the world can be used to image the structure of the Earth using tomographic approaches.

Seismic tomography, first introduced more than 40 years ago, is still a rapidly developing field, which provides the most important constraints to unravel our planet's present and past dynamics, and the driving forces for plate tectonics. In the last years, with the advent of new numerical methods, unprecedented data sets and more commonly available high performance computing resources, we have seen an outburst of 3D geophysical models and techniques for seismic imaging.

This talk will present recent developments and application of advanced multivariate inversion techniques to generate a realistic, comprehensive, and high-resolution 3D model of the seismic structure of the crust and upper mantle that satisfies several independent geophysical datasets - surface wave dispersion measurements, gravity data, teleseismic receiver functions, and seismic body wave travel times. Surface wave dispersion measurements are primarily sensitive to seismic shear-wave velocities, but at shallow depths it is difficult to obtain high-resolution velocities and to constrain the structure due to the depth-averaging of the more easily-modeled, longer-period surface waves. Gravity inversions have the greatest resolving power at shallow depths, and they provide constraints on rock density variations.

Moreover, while surface wave dispersion measurements are primarily sensitive to vertical shear-wave velocity averages, body wave receiver functions are sensitive to shear-wave velocity contrasts and vertical travel-times. Addition of seismic travel-time data helps to constrain the seismic velocities both vertically and horizontally in the model cells crossed by the ray paths. P-wave velocities and density variations are related to shear-speed using empirical velocity ratios and relations so that all datasets may be combined in a single inversion. We constrain the 3D variations to be laterally and vertically smooth.

I will present applications of the method to investigate the seismic velocity structure underneath several regions of interest and at different scales. The final optimized 3D velocity models allow us to explore how multi-parameter tomography addresses crustal heterogeneities in areas of limited coverage and improves travel time predictions as well as to address general tectonic and geodynamic questions. 

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  • Created By: nlawson3
  • Workflow Status: Published
  • Created On: Aug 24, 2017 - 11:41am
  • Last Updated: Aug 24, 2017 - 1:00pm