DC06 Olga Nesterova - Isamgeo
The goal of the project is to develop, test and validate monitoring tools based on seismic surface waves and particularly on the use of passive seismic sources (noise) for the assessment of natural risks and detailed characterization of the shallow subsurface, particularly in urban areas. The determination of detailed shallow subsurface structures in terms of shear wave velocity, the assessment of peak ground acceleration (as an effect of local seismic amplification) and the determination of anthropogenic underground structures also from backscattered energy migration are among the most obvious products of such a research plan, with important practical results in terms of local seismic response assessment and detailed understanding of urban subsoil structures for a number of management goals.
Mechanical waves are powerful diagnostic tools to detect heterogeneities in solid media. At least partially, their capabilities derive from their being easily scalable in terms of the used source frequencies, corresponding to scaled wavelengths, that can span a range from tens of km to a few mm or less. Among seismic waves, surface waves are a class of particular interest. Surface seismic waves have been used for decades for the near-surface subsoil characterization in engineering and environmental applications. The potential of seismic waves at a wide range of scale has not been fully exploited yet, while most of the theoretical apparatus and numerical tools are available or easily adapted across scales.
At the same time, the recent availability of spatially distributed low-cost seismic sensors (fibers, MEMS, etc) paves the ways for a more complete wavefield sampling in space, thus allowing for unprecedented information extraction from surface (as well as body) waves. This large availability of spatially distributed data calls, in turn, for suitable real time acquisition, processing and inversion algorithms that have never been used at this small scale, and yet are widely available (with adaptations) e.g. from acoustics and seismological network processing.
The combination of (a) novel acquisition tools, (b) adapted data processing approaches, and (c) novel strategies for surface wave inversion, represent the overall plan of this PhD project. A specific focus will be put on the use of passive seismic acquisition, i.e. on the use of natural and/or anthropogenic sources of diffused and uncontrolled origin, as the main acquisition strategy as opposed to cases where energy is purposely put into the ground via controlled seismic sources – the latter being generally more troublesome in terms of logistics and (perceived) environmental impact.
Keywords: Seismic micro-zonation, Local seismic response, Surface waves, Local seismic networks, Site effects
Research fields: Geosciences, civil engineering, environmental science
Click here to watch Olga introduce herself as well as her PhD subject.
DAS and MEMS have been widely used in different environments (e.g. oil wells for DAS, and many accelerometric
applications in the mechanical industry for MEMS). Yet their use in densely distributed networks for monitoring ambient noise in urban environments is still in its infancy. The main challenge lies in the capability to deploy dense networks and manage large datasets in order to retrieve spatially dense information in terms of both shallow subsoil characteristics and local seismic source localisation. These networks are designed to characterise the subsurface by means of direct, reflected, refracted and backscattered seismic waves, and particularly surface (Rayleigh) waves. The goal of the project is to develop, test and validate monitoring tools based on seismic surface waves and, more specifically, on the use of passive seismic sources (noise) for the assessment of natural risks and a detailed characterisation of the shallow subsurface, notably in urban areas. This effort will lead to determining detailed shallow subsurface structures in terms of shear wave velocity, an assessment of Peak Ground Acceleration (as an effect of local seismic amplification), and anthropogenic underground structures, also from backscattered energy migration.
1. Development and testing of inversion in 3D tomography (pointing towards shear wave velocity estimation) for urban environments
2. Development and testing of surface wave backscattering analysis algorithms, with special emphasis on the identification of sharp lateral discontinuities in the shallow subsurface, as often linked to man-made structures in complex settings accompanied by
3. the acquisition and processing of spatially dense accelerometric data, with the goal of producing spatially alias-free shake maps capable of estimating true PGAs in urban areas.
- ULB, Arnaud Deraemaeker, 2 months, M13-M14: Training on the numerical modelling of wave propagation.
- UBRI, Anthony Croxford, 2 months, M18-M19: Training on acoustic Non-Destructive Testing methods, paper writing.
- BAM, Vera Lay, 2 months, M25-M26: Testing of acquisition and processing strategies at the BAM test site.
- Barone I., E. Kästle, C. Strobbia and G. Cassiani, 2021, Surface Wave Tomography using 3D active-source seismic data, Geophysics, 86(1), A1-V89, doi: 10.1190/geo2020-0068-1.
- Barone I., J. Boaga, A. Carrera, A. Flores Orozco, G. Cassiani, 2021 Tackling lateral variability using surface waves: a tomography-like approach, Surveys in Geophysics, Vol. 42(2), 317-338, doi: 10.1007/s10712-021-09631-x
- Barone I., G. Cassiani, A. Ourabah, J. Boaga, M. Pavoni, R. Deiana, 2022, Surface wave tomography using dense 3D data around the Scrovegni Chapel in Padua, Italy, Scientific Reports, 12, 11806, doi: 10.1038/s41598-022-16061-1
Contact
Contact
DC06 Olga Nesterova
Contact
Local industrial supervisor Alessandro Brovelli
Contact
Academic co-supervisor Vera Lay
Contact
PhD supervisor Giorgio Cassiani