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  Thèse de Shipra Sethi

Modeling of Noise sources
Encadrant (et co-encadrant) : 

Seismic noise is recorded by broadband seismometers in the absence of earthquakes. It

is generated by the atmosphere-ocean system with different mechanisms in the different

frequency bands. Even though some mechanisms have been known for decades, an integrated

understanding of the noise in the broadband period band 1-300 sec is still missing. The

purpose of the PhD is to use novel theoretical, numerical and signal processing methods to

provide a unified understanding of the noise sources and quantitative models of the broadband


Most noise sources are located in the oceans, they vary over time and many sources

continuously generate seismic waves that propagate within the Earth in the broadband period

range 1-300sec. Depending on the period range, the source can be created by mutual

interactions of ocean waves or by the interaction of waves or infragravity waves with the

bathymetry at the coast.

Body waves provide useful information on noise sources but they are not directly

visible on seismic records because they are weak signals. The purpose of the PhD is to

develop novel signal processing and inversion tools and to apply them to detect body waves

in a data mining approach. The objective is to obtain spatio-temporal models of the sources.

These models will enable to better understand the noise generation in the broadband

frequency range. They will also be used to improve ocean wave models.

The second part of the PhD will be dedicated to the modelling of noise considering

seismic propagation in 3D Earth and to investigate the generation of the different waves, in

particular SH body waves and Love waves