Harvard Seismology: Normal Modes

The analysis of the normal modes of the Earth is one of the most active areas of current research in quantitative seismology. Long used to constrain source mechanisms, normal modes are now being studied as a way to constrain large-scale 3-D structure in the mantle and in the inner core. Here at Harvard, we have several ongoing projects designed both to help us understand and predict mode behavior as well as to use our knowledge of that behavior to teach us more about the Earth and its seismicity.

Active participants in these projects are Göran Ekström, and Miaki Ishii.

Previously active participants in these projects are Jeroen Tromp, Xiong He, Daniel Russakoff, and Eva Zanzerkia.

Recent Developments

Mantle modelling using mode splitting.

A new analysis of the Great Colombia earthquake of 7/31/70.

Fitting normal mode spectra.

Anomalously Split Modes.

Publications

• Ishii, M., & Tromp, J., 1999.
  Even-degree lateral variations in the mantle constrained by free oscillations and the free-air gravity anomaly. Geophys. J. Int. 145, 77-96.

• Ishii, M., & Tromp, J., 1999.
  Normal-mode and free-air gravity constraints on lateral variations in velocity and density of Earth's mantle. Science 285, 1231-1236.

• Russakoff, D., Ekström, G., & Tromp, J., 1997.
  A new analysis of the Great Colombia earthquake of 1970. J. Geophys. Res. 102, 20423-20434.

• He, X., & Tromp, J., 1996.
  Normal-mode constraints on the structure of the Earth. J. Geophys. Res. 101, 20053-20082.

• Tromp, J., & Zanzerkia, E., 1995.
  Toroidal splitting observations from the great 1994 Bolivia and Kuril Islands earthquakes. Geophysl. Res. Lett. 20(16), 2297-2300.