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EARTHQUAKE MAGNITUDE, INTENSITY, ENERGY, POWER LAW RELATIONS AND SOURCE MECHANISM

EARTHQUAKE MAGNITUDE, INTENSITY, ENERGY, POWER LAW RELATIONS AND SOURCE MECHANISM. J R Kayal Geological Survey of India Kolkata e-mail: jr_kayal@hotmail.com. EARTHQUAKE CLASSIFICATION MAGNITUDE CLASSIFICATION M ≥ 8.0 Great Earthquake 7.0 ≥ M < 8.0 Major / Large Earthquake

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EARTHQUAKE MAGNITUDE, INTENSITY, ENERGY, POWER LAW RELATIONS AND SOURCE MECHANISM

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  1. EARTHQUAKE MAGNITUDE, INTENSITY, ENERGY, POWER LAW RELATIONS AND SOURCE MECHANISM J R Kayal Geological Survey of India Kolkata e-mail:jr_kayal@hotmail.com

  2. EARTHQUAKE CLASSIFICATION MAGNITUDE CLASSIFICATION M ≥ 8.0 Great Earthquake 7.0 ≥ M < 8.0 Major / Large Earthquake 5.0 ≥ M < 7.0 Moderate Earthquake 3.0 ≥ M < 5.0 Small Earthquake 1.0 ≥ M < 3.0 Microearthquake M < 1.0 Ultra Microearthquake Hagiwara, 1964

  3. NATURE OF EARTHQUAKES • Foreshocks • Main shock • Aftershocks • Earthquake Swarm • Normal Seismic activity

  4. TYPES OF EARTHQUAKES • Tectonic Earthquake • Volcanic Earthquake • Collapse Earthquake • Explosion Earthquake CLASSIFICATION DISTANCE 1) Teleseismic Earthquake > 1000 km 2) Regional Earthquake > 500 km 3) Local Earthquake < 500 km

  5. EARTHQUAKE MAGNITUDE Richter Magnitude ML (Local Magnitude) ML = log A - log Ao ( ) Body-wave Magnitude (mb) Surface-wave Magnitude (Ms) Ms= log AHmax - log Ao (o) mb = log (A/T) - f (,h) MS = log (A/T)max + 1.66 log + 3.3 Moment Magnitude (Mw) Duration Magnitude (MD) Mw = 2/3 log Mo - 10.7 MD = - 0.87 + 2.00 log  + 0.0035  Mo = A u Macroseismic Magnitude (Mms) Mms = 0.5Io + log h + 0.35

  6. Richter Magnitude Scale Distance S – P Magnitude Amplitude km sec ML mm

  7. EARTHQUAKE INTENSITY • Rossi-Forel Intensity Scale (I – X) • Modified Mercalli (MM) Intensity Scale (1956 version), (I – XII) • Medvedev-Sponheuer-Karnik (MSK) Intensity Scale • (1992 Version), (I – XII) Isoseismals Isoseismals are the curved lines joining the localities of same intensity.

  8. Isoseismal of the 2001 Bhuj Earthquake, Mw 7.7

  9. Isoseismals of large earthquakes in India

  10. INTENSITY AND ACCELERATION log a = 2 or a=100 cm/sec2 = 0.1g,when I = 7 and a = 1g ,when I = 10 Richter, 1958

  11. EARTHQUAKE ENERGY log E = 12 + 1.8 ML log E = 5.8 + 2.4 mb log E = 11.4 + 1.5 Ms Magnitude versus ground motion and energy Magnitude Ground Motion Energy 1.0 10.0 times about 32 times 0.5 3.2 times about 5.5 times 0.3 2.0 times about 3 times 0.1 1.3 times about 1.4 times

  12. POWER LAW RELATIONS Frequency- magnitude Relation Log10N = a – bM Aftershock Attenuation (p-value) N(t)  t -p Fractal Dimension

  13. b - VALUE ESTIMATION The Least-Square Fit Method: The log values of the cumulative number of earthquakes (N) are plotted against magnitude (M). The Maximum Likelihood Method : The maximum likelihood estimate of b-value is given by Aki ( 1965) : b =log10e/M-M0

  14. b-value: b = 0.77 Log N Magnitude An example showing frequency-magnitude relationin NE India

  15. b-value Map Contour Map showing the variation of b-value in NE India

  16. p-value: p = 0.91 Log-Log Plot of no. of aftershocks with time

  17. Examples of Fractal Shapes Examples of Euclidean Shapes

  18. Fractal Dimension D2 = 1.56 Example of Correlation integral versus distance plot

  19. Fractal Map Contour Map showing variation of Fractal Dimension in NE India

  20. SOURCE MECHANISM (fault-plane solution) Classification of Faults • Thrust Fault • Normal Fault • Strike-slip Fault Dynamics of Faulting • Single Couple • Double Couple Elastic Rebound Theory

  21. Normal fault Regime Thrust fault Regime Strike-slip fault Regime

  22. Fault Dimension

  23. Different Types of Faulting

  24. Graben & Horst in Fault System

  25. Stress System Fracture Criteria: Mohr Circle

  26. Dynamics of Faulting

  27. Elastic Rebound Theory Reid, 1910

  28. Plotting of P-wave First-motion (Equal Area Projection)

  29. Equal Area Plot of a Plane and its Pole

  30. P-wave first-motion plot and fault plane solution Kayal, 1984

  31. Source mechanisms of earthquakes at spreading centre

  32. Source mechanisms of earthquakes at the subduction zone, Indo-Burma ranges Rao & Kalpana, 2005

  33. Source mechanisms of earthquakes at the Himalayan collision zone Ni & Barazangi, 1984

  34. Source mechanisms of intraplate earthquakes, peninsular India Kayal, 2000

  35. ( Kayal 2000, JGS )

  36. ( Kayal, 2000 JGS )

  37. (a) Fault-plane solutions of the Bhuj earthquakes (b) N-S depth section of the earthquakes (Kayal et al. 2002, JGS )

  38. Seismotectonic Model of 26th January, 2001 Bhuj Earthquake (Kayal et al. 2002, JGS )

  39. Thank you

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