This is a kind reminder of our next “Talks on GIA” seminar which will be
next week on Wednesday, 29 January 2025 at
UTC: 18:00/6:00pm | PST: 10:00am | EST: 13:00am | CET: 19:00/7:00pm |
CST: 02:00 (30 Jan) | AEDT: 05:00 am (30 Jan)
https://everytimezone.com/s/9675de4c
Please click here to join the meeting, with Passcode: ToGIA_24
The topic will be:”Modeling mantle rheology between the seismic and post-glacial rebound time scales: the Extended Burgers Material”
presented by: Lambert Caron (Jet Propulsion Lab, California Institute of Technology, Pasadena, USA)
The extended Burgers material (EBM) model provides a linear viscoelastic
theory for interpreting a variety of rock deformation phenomena in
geophysics, playing an increasingly important role in parameterizing
laboratory data, providing seismic wave velocity and attenuation
interpretations, and in analyses of solid planetary tidal dispersion and
quality factor /Q/. At the heart of the EBM approach is the assumption
of a distribution of relaxation spectra tied to rock grain boundary and
interior granular mobility. The model also captures an asymptotic
long-term limiting behavior that is Maxwellian. Using newly developed
Love number computation capability in the Ice-sheet and Sea-level System
Model (ISSM), we compute a large ensemble of models exploring an EBM
parameter space including distinct upper and lower mantle properties. We
compare the resulting tidal Love numbers with constraints derived from
satellite laser ranging (SLR), satellite gravity time series, geodetic
observations of the Earth rotation rate and polar motion, and Global
Navigation Satellite Systems (GNSS), for periods ranging from 12 hours
to 18.6 years. We find that models with EBM rheology successfully meet
these constraints while retaining a steady-state viscosity consistent
with those derived from glacial isostatic adjustment analysis.
Importantly, the body tide deformation results are sensitive to the
short-term rheology of the lower mantle. We highlight significant
parameter correlation between the timescale and amplitude of the
transient relaxation, such that both fast low-amplitude relaxation and
slow high-amplitude solutions appear compatible with observations. New
constraints on EBM parameters have direct application to geodetic
studies of glacial isostatic adjustment, especially when surface loading
includes the rapid changes in the cryosphere and sea level occurring
during the 20th and 21st centuries.
© 2024 California Institute of Technology. Government Sponsorship
Acknowledged.
We are very much looking forward to the presentation and many participants.
Best wishes on behalf of all “Talks on GIA” organizers!
—
Dr. Matthias O. Willen