Anne Obermann

Senior Researcher, Lecturer

Swiss Seismological Service, ETH

Zurich, Switzerland


Research Interests

Keywords: Seismology, ambient seismic noise, seismic interferometry, coda waves, volcanoes and active faults monitoring

In November 2013 I finished my PhD at ISTerre (Grenoble, France) under the supervision of Michel Campillo and Eric Larose. I have worked on different aspects of monitoring the elastic properties of the crust, with both numerical analysis and applications with ambient seismic noise.

With the numerical studies, we investigated the depth sensitivity of coda waves in heterogeneous media. This work allowed us to relate the depth sensitivity of coda waves to a combination of bulk wave sensitivity and surface wave sensitivity that depends on the time in the coda and on the scattering mean free path of the medium. We could show a time dependence of the relative velocity changes in the coda that allows us to discriminate a change that occurs at the surface from a change that occurs at depth.

Besides these numerical studies, I am interested in the localisation of deformations in the crust associated with major hazardous events such as volcanic eruptions and earthquakes using continuously available records of ambient seismic noise. Within this context, we developed an inversion method based on probabilistic approaches for the wave propagation to locate changes in the medium. I applied and refined this inversion method with three case studies. We studied pre-and co-eruptive changes at Piton de la Fournaise volcano in La Reunion Island. The challenge here was to correctly locate the forthcoming eruption. We then applied the method to a unique data set from the Wenchuan Seismological Array, that was operational during the Mw7.9, 2008 Wenchuan earthquake in China. In this study, we take the time evolution of the coda into account and jointly invert the data at different times in the coda to study changes at the lower and middle crust, which significantly increases the resolution. Lately, we implemented a 3D sensitivity kernel into the inversion procedure and used it to study the fracturing of concrete blocks under increased tension.