John Paul O'Donnell
- Position: Research Fellow
- Email: J.P.ODonnell@leeds.ac.uk
When an earthquake occurs, part of the energy released radiates outward from the rupture in the form of seismic waves. As these waves travel through the Earth they are continually altered by the structures they encounter. By decoding the information imprinted on the waveforms seismologists learn about the internal structure of the Earth. In particular, by combining the information garnered from a large number of earthquakes seismologists can effectively image the internal 3D structure of the Earth. These so-called seismic tomography models help us understand the dynamic Earth.
- Postdoc, University of Leeds, 2015-present
- Postdoc, The Pennsylvania State University, 2011-2015
- PhD Geophysics, 2005-2010, The National University of Ireland, Galway
- Higher Diploma in Education, 2004-2005, University College Dublin
- BA Mod Theoretical Physics, 1999-2003, Trinity College Dublin
I’ve used seismic waves to study the lithosphere and uppermost mantle in several regions to different ends: in Ireland to probe for signatures of the ancient Iapetus suture, in eastern Africa to better understand the evolution of the East African Rift System and in Antarctica to explore the structure of the West Antarctic Rift System. At Leeds, I will use seismic tomography to image the structure of the lithosphere and upper mantle beneath the Antarctic Peninsula and Ellsworth Land. In a roundabout way, this information will help predict the effect that the evolving West Antarctic Ice Sheet will have on global sea-level change:
Fluctuations in the ice sheet mass cause fluctuations in the Earth’s gravity field, so gravity data can be used to track ice loss. However, the total gravity signal also reflects other Earth structures and processes, the most problematic of which is Glacial Isostatic Adjustment (GIA). During GIA, mass within the Earth’s mantle slowly flows back toward equilibrium following the addition (advance) or subtraction (retreat) of a significant surface ice load. The extreme viscosity of the Earth’s mantle means that this internal mass re-distribution can lag the actual ice sheet advance or retreat by thousands of years. Therefore, we can only isolate the gravity signal caused by present ice mass change by removing the GIA signal caused by the past behaviour of the ice sheet. To do this, we must know both the ice sheet history and the viscosity of the mantle. However, knowledge of mantle viscosity remains elusive. Temperature is considered the dominant control on mantle viscosity. Since seismic wave propagation in the Earth is particularly sensitive to thermal variations, seismology is an ideal tool to probe mantle viscosity.
The UK Antarctic seismic network (UKANET) consists of 10 broadband stations located across the southern Antarctic Peninsula and Ellsworth Land in West Antarctica that will record seismic energy from earthquakes occurring worldwide over a two-year period. The stations will record concurrently with partner US Polar Earth Observing Network (POLENET) stations over the first year of the deployment, enhancing our capability to probe Earth structure. Our analysis of the data will ultimately recover the thermal signature (and hence viscosity) of the underlying mantle encoded in the recorded waveforms.
- Johnson, J. S., O’Donnell, J. P. and Thomas, E. R., 2018. In situ measurements of snow accumulation in the Amundsen Sea Embayment during 2016. Antarct. Sci., 30(3), 197-203, https://doi.org/10.1017/S095410201800006
- O'Donnell, J. P., Shamsalsadati, S., Brazier, R. A. and Nyblade, A. A., 2017. Locations and Source Parameters for Calibration Events in Turkey, Saudi Arabia, Ethiopia, and Tanzania. Bull. Seismol. Soc. Am., 108(1), 145-154, http://doi.org/10.1785/0120170180
- O'Donnell, J. P., Selway, K., Nyblade, A. A., Brazier, R. A., Wiens, D. A., Anandakrishnan, S., Aster, R. C., Huerta, A. D., Wilson, T. and Winberry, J. P., 2017. The uppermost mantle seismic velocity and viscosity structure of central West Antarctica. Earth Planet. Sci. Lett., 472, 38-49, http://doi.org/10.1016/j.epsl.2017.05.016
- Accardo et al., 2017. Surface-wave imaging of the weakly-extended Malawi Rift from ambient-noise and teleseismic Rayleigh waves from onshore and lake-bottom seismometers. Geophys. J. Int., 209, 1892-1905, https://doi.org/10.1093/gji/ggx133
- Shillington et al., 2016. Acquisition of a unique onshore/offshore geophysical and geochemical dataset in the Northern Malawi (Nyasa) Rift. Seismol. Res. Lett., 87(5), http://dx.doi.org/10.1785/0220160112
- O’Donnell, J. P., Selway, K., Nyblade, A. A., Brazier, R. A., El Tahir, N. and Durrheim, R. J., 2016. Thick lithosphere, deep crustal earthquakes and no melt: a triple challenge to understanding extension in the western branch of the East African Rift. Geophys. J. Int., 204, 985-998, http://dx.doi.org/10.1093/gji/ggv492
- O’Donnell, J. P. and Nyblade, A. A., 2014. Antarctica’s hypsometry and crustal thickness: Implications for the origin of anomalous topography in East Antarctica. Earth Planet. Sci. Lett., 388, 143-155, http://dx.doi.org/10.1016/j.epsl.2013.11.051
- O’Donnell, J. P., Adams, A., Nyblade, A. A., Mulibo, G. D. and Tugume, F., 2013. The uppermost mantle shear wave velocity structure of eastern Africa from Rayleigh wave tomography: Constraints on rift evolution. Geophys. J. Int., 194, 961-978, http://dx.doi.org/10.1093/gji/ggt135
- Boomer, K. B., Brazier R. A., O’Donnell, J. P., Nyblade, A. A., Kokoska, J. and Liu, S., 2013. From Craton to Rift: Empirically Based Ground Truth Criteria for Local Events Recorded on Regional Networks, Bull. Seismol. Soc. Am., 103(4), 2295-2304, http://dx.doi.org/10.1785/0120120276.
- O’Donnell, J. P., Daly, E., Tiberi, C., Bastow, I. D., O’Reilly, B. M., Readman, P. W. and Hauser, F., 2011. Lithosphere-asthenosphere interaction beneath Ireland from joint inversion of teleseismic P-wave delay times and GRACE gravity. Geophys. J. Int., 184, 1379-1396, http://dx.doi.org/10.1111/j.1365-246X.2011.04921.x