Introduction to Active Tectonics and Deformation Modeling

4. GE177b- Objectives • Introduce a variety of techniques to describe ‘quantitatively’ deformation of the lithosphere and fault slip history. • Introduce the basic mechanisms governing lithospheric deformation and conceptual models of the ‘seismic cycle’. • Expose the students to a number of modeling tools commonly used in tectonics studies. I will try to lead you to think not only in terms of kinematics but also in terms of stress and rheology.

5. GE177b- Objectives At the end of the class you should be able • to carry on a active tectonic studies on your own using satellite images, DEM and able to plan a field survey. (Observe, Measure) • to analyze the results based of general concepts in tectonics and simple modeling tools (Interpret, Model) • to read and assess the current literature in active tectonics (Critical Reading)

6. I. Introduction to Active Tectonics • Objectives: • Introduce some outstanding issues in continental tectonic and seismotectonics. • Give an overview of the tools and concepts that will be addressed over the course of the class.

8. Topography and seismicity suggests continental deformation is distributed

9. Where are the active faults? Velocities relative to Eurasia, Bettinelli et al (2006), Calais et al (2006), Simons et al (2007), Gan et al (2007), Chlieh et al (2010)

10. Satellite Mosaic and topography of Central Asia The response is in the landscape

11. (Tapponnier and Molnar, 1975)

12. Some outstanding issues in Active Tectonics • Is continental deformation distributed or localized? (Is it appropriate to model continental lithosphere as a viscously deforming medium or an elasto-plastic medium? ) • What is the influence of surface processes on tectonics?

13. Coupling between Tectonics, Erosion and Climate Isostatic response to valley deepening might lead to peak uplift (England and Molnar, 1990)…

14. Some outstanding issues in Active Tectonics • Is continental deformation distributed or localized? (Is it appropriate to model continental lithosphere as a viscously deforming medium or an elasto-plastic medium? ) • What is the influence of surface processes on tectonics? • Is continental deformation a ‘side effect’ of plate tectonics or does it play an important role in global dynamics?

15. Plate motion of India relative to Eurasia (Copley et al, 2010)

16. Some outstanding issues in Active Tectonics • Is continental deformation distributed or localized? (Is it appropriate to model continental lithosphere as a viscously deforming medium or an elasto-plastic medium? ) • What is the influence of surface processes on tectonics? • Is continental deformation a ‘side effect’ of plate tectonics or does it play an important role in global dynamics? • What factors determine the relative proportion of seismic and aseismic deformation? (What determines whether a fault patch creeps steadily or produce seismic slip?) • How regular/irregular is the ‘seismic cycle’ on a fault?

17. The ‘Seismic Cycle’ jargon • Motion on faults is generally ‘stick-slip’. Some fault creeps aseismically but most produce recurring large earthquakes. • Conventionnally we distinguish • Co-seismic deformation • Interseismic deformation • Post-seismic deformation • Secular deformation (long term averaged)

18. Secular deformation results only from slip on the thrust fault

19. Secular deformation might result from slip on the thrust fault and distributed deformation within the orogenic wedge

20. Interseismic deformation might be non stationnary

21. Reality might lool more like this…

22. Some outstanding issues in Active Tectonics • Is continental deformation distributed or localized? (Is it appropriate to model continental lithosphere as a viscously deforming medium or an elasto-plastic medium? ) • What is the influence of surface processes on tectonics? • Is continental deformation a ‘side effect’ of plate tectonics or does it play an important role in global dynamics? • What factors determine the relative proportion of seismic and aseismic deformation? (What determines whether a fault patch creeps steadily or produce seismic slip?) • How regular/irregular is the ‘seismic cycle’ on a fault? • Are some aspects of the ‘seismic cycle’ predictable? (rupture extent, magnitude, time, slip, …) • How do faults interact? Does it lead to some systematic pattern? • What is the rheology governing fault bevavior? • ….

23. What information/observations do we need to make progress on these issues? • Good kinematic description of crustal deformation and fault behavior : • active faults • long-term slip rates, • Information about mode of slip (paleoseismo, paleogeodesy) • coseismic slip models • interseismic strain and interseismic coupling models… • Constraints on stresses…

24. GE177b-Outline I. Introduction to Active Tectonics II. Methods in Morphotectonics III. Determining the time evolution of fault slip IV. The ‘seismic cycle’ Appendices: - A: Geochronologic methods in Active Tectonics - B: Geodetic and Remote Sensing techniques - C: Elastic Dislocation Modeling