Seismology and data processing

This module introduces the basics of seismology. It focuses on the initiation of earthquakes, wave propagation and the analysis of recordings to characterize the earthquake (location, magnitude, focal mechanism) and image the Earth's interior. We'll also look at estimating the seismic hazard of earthquakes. Finally, we'll look at how this information enables us to better understand geodynamics and the seismic cycle. The second part of the course focuses on the processing of seismograms, with an introduction to signal processing techniques through computer exercises (Fourier transform, filter, convolution, correlation) and imaging/tomography. The year concludes with a practical course on real data, including data plotting, magnitude calculations, and the location and mechanism of an earthquake focus to characterize and quantify active deformation in the East African Rift.  

Hourly volumes:

• CM: 25h
• TD: 12h
• Practical work: 8h

By the end of the module, students will be able to:

• Understand the relationship between stress, strain and the seismic cycle
• Understand why and how seismology is used to image the Earth's interior.
• Characterize an earthquake (location, magnitude, focal mechanism)

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

• Mathematical concepts: trigonometry, vectors, equations (degree 1 and 2), derivation, integration, gradient.
• Physics concepts: force balance, 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 :

• Concepts of stress, strain, Hooke's law, modulus of elasticity and Poisson's ratio. Domains of deformation 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)
• Earthquake location and magnitude, focus mechanism
• Seismic tomography and link to physical parameters (temperature, pressure, lithology, fluids)
• Introduction to deterministic and probabilistic seismic hazards
• Introduction to paleoseismology
• • Major earthquakes and tsunamis
  • Introduction to signal processing (Fourier transform, filter, correlation, convolution)

Summary description of TD sessions and number of hours associated with each session

• Notion 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, focus mechanism (3h)
• Seismic tomography and link with physical parameters (temperature, pressure, lithology, fluids) (1.5h)
• Introduction to deterministic and probabilistic seismic hazard (3h)

Summary description of practical sessions and number of hours for each session

• Fourier transform and filtering of simple signals (sum of sines or cosines) and real data

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