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 earthquakes (location, magnitude, focal mechanism) and image the Earth's interior. We will also discuss earthquake hazard assessment. Finally, we will look at how this information allows us to better understand geodynamics and the seismic cycle. The second part of the course focuses more specifically on the processing of seismograms, with an introduction to signal processing techniques during computer lab sessions (Fourier transform, filtering, convolution, correlation) and imaging/tomography. A tutorial using real data concludes the year with data plotting, magnitude calculation, and the location and mechanism of an earthquake focus to characterize and quantify the active deformation of the East African Rift.  

Hourly volumes:

• CM: 25 hours
• TD: 12 p.m.
• Practical work: 8 hours

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

• To understand the relationship between stress, deformation, and the seismic cycle
• To understand why and how seismology can be used to image the interior of the Earth
• To characterize an earthquake (location, magnitude, focal mechanism)

They also have a good grasp of the basics of seismic data processing and seismic hazard assessment.

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

Recommended prerequisites:

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

• Concepts of continuum mechanics and wave physics (period, frequency)
• Concepts of partial derivatives and partial equations

Continuous assessment

Brief description of the concepts covered in CM:

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

Brief description of tutorial sessions and number of hours associated with each session

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

Brief description of practical sessions and number of hours associated with each session

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

• Understand Hooke's law and know how to relate stress, strain, modulus of elasticity, and Poisson's ratio.
• Understanding deformation zones up to rupture: linking the seismic cycle, deformation styles observable on the surface (folds, faults), and rheological behavior with depth.
• Calculate the magnitude of an earthquake, estimate its location and the mechanism at the focus
• Understanding how a seismic tomography image is obtained and knowing how to interpret it (lithology, temperature, fluids)
• Estimating seismic hazard in a simple case