Seismology and data processing

This module introduces the basics of seismology. It focuses on the initiation of earthquakes, wave propagation and analysis of recordings to characterize the earthquake (location, magnitude, mechanism at the focus) and to image the interior of the Earth. We will also deal with the estimation of the seismic hazard of earthquakes. We will finally look at how this information allows us to better understand the geodynamics and the seismic cycle. A second part of the course focuses on the processing of seismograms with an introduction to signal processing techniques during computer exercises (Fourier transform, filter, convolution, correlation) and imaging/tomography. A practical course with real data concludes the year with the pointing of data, the calculation of magnitudes, the localization and the mechanism of an earthquake focus to characterize and quantify the active deformation of the East African Rift.  

Hourly volumes:

• CM : 25h
• TD : 12h
• TP : 8h

Students are able to, at the end of the module:

• To understand the relationship between stress, strain and the seismic cycle
• To understand why and how seismology can image the interior of the Earth
• Characterize an earthquake (location, magnitude, mechanism at the focus)

They also master the basics of seismic data processing and seismic hazard estimation.

• Mathematical concepts: trigonometry, vectors, equations (degree 1 and 2), derivation, integration, gradient
• Notions in physics: balance of forces, work, force, energy, conservation equation

Recommended prerequisites:

• Geoscience concepts: plate tectonics, main interfaces of the earth's structure

• Notions of continuous media mechanics and wave physics (period, frequency)
• Notions of partial derivatives and partial equations

Continuous control

Synthetic description of the concepts covered in CM:

• Concept of stress, strain, Hooke's law, modulus of elasticity and Poisson's ratio. Deformation domains up to failure: link with the seismic cycle, deformation styles observable at the surface (folds, faults) and rheological behavior with depth
• Wave propagation (equation, phenomena at interfaces, hodochrones)
• Location and magnitude of an earthquake, mechanism at the focus
• Seismic tomography and link with physical parameters (temperature, pressure, lithology, fluids)
• Introduction to deterministic and probabilistic seismic hazard
• Introduction to paleoseismology
• • Large earthquakes and tsunamis
  • Introduction to signal processing (Fourier transform, filter, correlation, convolution)

Synthetic description of the TD sessions and number of hours associated with each session

• Concept of stress, strain, Hooke's law, modulus of elasticity and Poisson's ratio. Deformation domains up to failure: link with the seismic cycle, deformation styles observable at the surface (folds, faults) and rheological behavior with depth (3h)
• Wave propagation equation (1.5h)
• Location and magnitude of an earthquake, mechanism at the focus (3h)
• Seismic tomography and link with physical parameters (temperature, pressure, lithology, fluids) (1.5h)
• Introduction to deterministic and probabilistic seismic hazard (3h)

Synthetic description of the practical sessions and number of hours associated with each session

• Fourier transform and filtering of simple signals (sum of sine or cosine) and real data

• Know Hooke's law and be able to relate stress, strain, modulus of elasticity and Poisson's ratio.
• Know the deformation domains until rupture: make the link with the seismic cycle, the deformation styles observable on the surface (folds, faults) and the rheological behavior with depth
• Calculate the magnitude of an earthquake, estimate its location and the mechanism at the focus
• Understand how a seismic tomography image is obtained and how to propose an interpretation (lithology, temperature, fluids)
• Estimate the seismic hazard in a simple case