Research
My research so far has been mostly interdisciplinary, being at the boundary between solid Earth geophysics, physical oceanography and atmospheric science. I have been developing theories, performing numerical simulation and carrying out data analysis using a variety of methods, tools and kind of data typical of these three disciplines.
Below is a(n incomplete) list of topics I have been working on, with a record of some related peer-reviewed publications.
The focus of my current research lies in physical oceanography and concerns the study of the vertical mixing, circulation and sea state of the Mediterranean Sea by means of numerical simulations.
Mobile Earthquake Recorder in Marine Areas by Independent Divers (MERMAIDs)
The origin of the ambient seismic (noise) wavefield
The ground is never truly at rest. A quasi-random signal, independent from the earthquake activity, is recorded continuously everywhere on Earth. This background seismic wavefield is mainly due to ocean storms driven by atmospheric disturbances. Historically called microseisms, the seismic background of the Earth generated by at the ocean surface is often referred to as seismic ambient noise. We are interested in advancing our understanding of the physical mechanisms lying behind the generation of seismic ambient noise across the whole spectrum (seismic hum, primary microseisms, and secondary microseisms) through 2-D and 3-D numerical simulations. This process -- known as the forward problem -- allows us to make and test hypotheses on the location and characteristics of the sources of ambient noise.
Some related publications:
Gualtieri, L., Bachmann, E., Simons, J. F., Tromp, J., 2021, Generation of secondary microseism Love waves: effects of bathymetry, 3D structure, and source seasonality, Geophysical Journal International, 226(1), 192-219, doi:10.1093/gji/ggab095.
Gualtieri, L., Bachmann, E., Simons, J. F., Tromp, J., 2020. The origin of secondary microseism Love waves, Proceedings of the National Academy of Sciences, 117(47), 29504-29511, doi:10.1073/pnas.2013806117.
BOOK: Nakata, N., Gualtieri, L. and Fichtner, A. (Authors & Editors.), 2019, Seismic Ambient Noise, 372 pages, Cambridge University Press, Cambridge, UK.
BOOK CHAPTER: Ardhuin, F., Gualtieri, L. and Stutzmann, E. 2019, Physics of ambient noise generation by ocean waves. Book chapter in Seismic Ambient Noise, N. Nakata, L. Gualtieri and A. Fichtner (eds.), Cambridge University Press.
Gualtieri, L., Stutzmann, E., Juretzek, C., Hadziioannou, C., Ardhuin, F., 2019, Global-scale analysis and modeling of primary microseisms, Geophysical Journal International, 218(1), 560–572, doi:10.1093/gji/ggz161.
Gualtieri, L., Stutzmann, E., Capdeville, Y., Farra, V., Mangeney, A., Morelli, A., 2015, On the shaping factors of the secondary microseismic wavefield, Journal of Geophysical Research - Solid Earth, 120(9), 6241−6262, doi:10.1002/2015JB012157
Ardhuin, F., Gualtieri, L., Stutzmann, E., 2015, How ocean waves rock the Earth: two mechanisms explain seismic noise with periods 3 to 300 s, Geophysical Research Letters, 42(3), 765−772, doi:10.1002/2014GL062782.
Gualtieri, L., Stutzmann, E., Farra, V., Capdeville, Y., Schimmel, M., Ardhuin, F., Morelli, A., 2014, Modelling the ocean site effect on seismic noise body waves, Geophysical Journal International, 197(2), 1096−1106, doi:10.1093/gji/ggu042.
Gualtieri, L., Stutzmann, E., Capdeville, Y., Ardhuin, F., Schimmel, M., Mangeney, A., Morelli, A., 2013. Modeling secondary microseismic noise by normal mode summation, Geophysical Journal International, 193(3), 1732−1745, doi:10.1093/gji/ggt090.
Environmental seismology: exploring surface processes with seismic data
Coupling between Atmosphere, Ocean and Solid Earth
Being that 70% of the surface of our planet is covered by the ocean, the seismic signals generated by ocean storms represent the vast majority of the seismic data any seismometer on Earth can record. Long considered “noise” by those using signals from earthquakes, the ambient seismic wavefield is generated continuously by the coupling between the ocean-atmosphere system, and the solid Earth. Studying the energy exchange among these three systems is one of the next Seismological Grand Challenges. We use modern data analysis techniques (e.g. machine learning, beamforming) and numerical modeling to assess characteristics of events in the ocean and the atmosphere through seismology.
Some related publications:
Retailleau, L. & Gualtieri, L., 2021, Multi-phase seismic source imprint of tropical cyclones, Nature Communications, 12, 2064, doi:10.1038/s41467-021-22231-y.
BOOK: Nakata, N., Gualtieri, L. and Fichtner, A. (Authors & Editors.), 2019, Seismic Ambient Noise, 372 pages, Cambridge University Press, Cambridge, UK.
Retailleau & Gualtieri, L., 2019, Toward high-resolution period-dependent seismic monitoring of tropical cyclones, Geophysical Research Letters, 46(3), 1329−1337, doi:10.1029/2018GL080785.
Gualtieri, L., Camargo, J.S., Pascale, S., Pons, F.M.E., Ekström, G., 2018, The persistent signature of tropical cyclones in seismic ambient noise, Earth and Planetary Science Letters, 484, 287−294, doi:10.1016/j.epsl.2017.12.026.
Mass-wasting events as sources of seismic waves
Mass-wasting events, like landslides and rockfalls, generate seismic waves as the mobilized mass accelerates and decelerates, sliding along the ground. The moving mass accelerates and decelerates during the sliding because of the forces that the Earth exercise on it: gravity, friction, and centripetal forces. According to Newton’s third law, these forces have reactive counterparts in the opposite direction, which are responsible for loading and unloading the ground and generating seismic waves. Using various analytical and numerical methods, we model the seismic signals generated by rockfalls and landslides, as recorded at the local and regional scale, to understand their dynamics and the characteristics of the moving center of mass.
Some related publications:
Gualtieri, L. & Ekström, G., 2017, Seismic reconstruction of the 2012 Palisades rockfall using the analytical solution to Lamb’s problem, Bulletin of the Seismological Society of America, 107(1), 63 − 71, doi:10.1785/0120160238.
Gualtieri, L. & Ekström, G., 2018, Broadband analysis and modeling of the 2015 Taan Fjord, Alaska landslide using Instaseis, Geophysical Journal International, 213, 1912−1923, doi:10.1093/gji/ggy086.
Scanning the Earth's interior: seismic tomography
Seismic tomography is one of the most powerful tools to investigate the internal structure of our planet. Conceptually similar to medical imaging based on ultrasound recordings, seismic tomography translates recordings of seismic waves into 3-D models of the subsurface at scales ranging from few meters to thousands of kilometers. Our group is interested in developing new methods for imaging the Earth's interior and investigating Earth's properties.
Some related publications:
Magrini, F., Boschi, L., Gualtieri, L., Lekic, V., Cammarano, F. (2021), Brittle-ductile transition in continental crust revealed by Rayleigh-wave attenuation, Scientific Reports, 11, 10149, doi:10.1038/s41598-021-89497-6.
Gualtieri, L., P. Serretti, and A. Morelli (2014), Finite-difference P wave travel time seismic tomography of the crust and uppermost mantle in the Italian region, Geochem. Geophys. Geosyst., 15, 69–88, doi:10.1002/2013GC004988.