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Earthquakes and crustal Deformation - Objectives of class-

Explores deformation of lithosphere, seismic mechanisms, tectonic modeling, and seismic potential factors like subduction rate and stress distribution. Discusses active faults, strain rate, seismic hazard analysis methodologies, and the role of fluids in fault dynamics.

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Earthquakes and crustal Deformation - Objectives of class-

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  1. Earthquakes and crustal Deformation- Objectives of class- • 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’. • Introduce 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.

  2. What factors determine the seismic potential of subduction zone? • Subduction rate? • Sea floor age? • Sea floor roughness? • Sediments? • A combination of these factors? (Heuret et al,G3, 2011)

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

  4. Topography and seismicity suggests continental deformation is distributed Where are the active faults?

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

  6. (Tapponnier and Molnar, 1975)

  7. Strain Rate from GPS - What fraction of geodetic strain is elastic and building up stresses to be released in future earthquakes? - Is ‘interseismic strain ‘stationnary’

  8. Some outstanding issues in Active Tectonics • Is continental deformation distributed or localized? • What factors determine the seismic potential of a fault, a faults system or a plate boundary? • What factors determine the relative proportion of seismic and aseismic slip on a fault? • How do earthquakes initiate? • What determines how large an earthquake will end once seismic rupture is initiated? • How can we probe the stress distribution on faults? • What factors determine the level of ground shaking? • What factors determine sea floor displacement (hence the tsunamigenic potential) during a subduction earthquake? • How are fluids involved in fault dynamics?

  9. Why should we care about fluids? • The brittle crust is permeated with fluids of various nature (water, brines, gas) and various origin (meteoric, formation fluids, metamorphic fluids) • Direct observations showing that fluids can induce earthquakes. • We would like to understand better the relationship between seismicity and fluid flow for Geothermy, Oil and Gas recovery, CO2 storage…

  10. Seismic Hazard Analysis, Current Practice • Where do earthquakes occur? • How often will they happen and how large can they get? • How hard will they shake the ground? • When answers are available for Steps 1-3: Add up all of the sources to find the probability of exceeding damaging shaking.

  11. Hazard model for the central and eastern U. S. primarily based on past seismicity What rate of earthquakes should be expected in the future? (Ellsworth, Science, 2013)

  12. Hazard model for the central and eastern U. S. primarily based on past seismicity Higher rate of earthquakes implies higher hazard. But how much higher? And where has the hazard increased? (Ellsworth, Science, 2013)

  13. 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 rheology of faults zone and the crust • Constraints on stresses…

  14. Dynamic Modeling the Parkfield EQs Sequence on the San AF [Barbot et al, Science, 2012] How to calibrate and validate such models?

  15. I. Introduction • II. Methods in Morphotectonics • III. Methods in Geodesy an Remote sensing • IV. Relating strain, surface displacement and stress, based on elasticity • V. Fault slip vs time • VI. Learnings from Rock Mechanics • VII. Case studies

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