The upper mantle geoid: Implications for continental structure and the intraplate stress field
[1];
- Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
- New Mexico Inst. of Mining and Technology, Socorro, NM (United States). Dept. of Earth and Environmental Science
- Univ. of Arizona, Tucson, AZ (United States). Dept. of Geosciences
- Univ. of Melbourne (Australia). School of Earth Sciences
We use the fact that geoid anomalies are directly related to the local dipole moment of the density-depth distribution to help constrain density variations within the lithosphere and the associated tectonic stresses. The main challenge with this approach is isolating the upper mantle geoid contribution from the full geoid (which is dominated by sources in the lower mantle). Here, we address this issue by using a high-pass spherical harmonic filtering of the EGM2008–WGS 84 geoid to produce an “upper mantle” geoid. The tectonic implications of the upper mantle are discussed in terms of plate tectonics and intraplate stresses. We find that globally there is a ~9 m geoid step associated with the cooling oceanic lithosphere that imparts a net force of ~2.5 × 1012 N/m in the form of “ridge push”—a magnitude that is consistent with one-dimensional models based on first-order density profiles. Furthermore, we find a consistent 6 m geoid step across passive continental margins which has the net effect of reducing the compressive stresses in the continents due to the ridge push force. Furthermore, we use the upper mantle geoid to reevaluate the tectonic reference state which previous studies estimated using an assumption of Airy-based isostasy. Our evaluation of the upper mantle geoid confirms the near-equivalence of the gravitational potential energy of continental lithosphere with an elevation of ~750 m and the mid-ocean ridges. This result substantiates early conclusions about the tectonic reference state and further supports the prediction that continental regions are expected to be in a slightly extensional state of stress.
- Research Organization:
- Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
- Sponsoring Organization:
- National Science Foundation (NSF); USDOE
- Grant/Contract Number:
- 89233218CNA000001; EAR-0607808
- OSTI ID:
- 1526946
- Report Number(s):
- LA-UR-17-22883
- Journal Information:
- Geological Society of America, Special Paper, Vol. 514; ISSN 0072-1077
- Country of Publication:
- United States
- Language:
- English
Similar Records
Tectonic subsidence, geoid analysis, and the Miocene-Pliocene unconformity in the Rio Grande rift, southwestern United States: Implications for mantle upwelling as a driving force for rift opening
Oceanic intraplate earthquakes: Implications for local and regional intraplate stress