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 MAGNITUDECLASSIFICATION 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 1)Foreshocks 2)Main shock 3)Aftershocks 4)Earthquake Swarm 5)Normal Seismic activity

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

5. EARTHQUAKE MAGNITUDE Richter Magnitude M L (Local Magnitude) M L = log A - log Ao (  ) Body-wave Magnitude (m b ) m b = log (A/T) - f ( ,h) Surface-wave Magnitude (M s ) M s = log AHmax - log Ao (  o) M S = log (A/T)max + 1.66 log  + 3.3 Moment Magnitude (M w ) M w = 2/3 log Mo - 10.7 M o =  A  u Duration Magnitude (M D ) M D = - 0.87 + 2.00 log  + 0.0035  Macroseismic Magnitude (M ms ) M ms = 0.5Io + log h + 0.35

6. Richter Magnitude Scale Distance S – P Magnitude Amplitude km sec M L 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, M w 7.7

9. Isoseismals of large earthquakes in India Isoseismals of large earthquakes in India

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

11. EARTHQUAKE ENERGY log E = 12 + 1.8 M L log E = 5.8 + 2.4 m b log E = 11.4 + 1.5 M s 1.010.0 timesabout 32 times 0.5 3.2 timesabout 5.5 times 0.3 2.0 timesabout 3 times 0.1 1.3 timesabout 1.4 times Magnitude Ground Motion Energy Magnitude versus ground motion and energy

12. POWER LAW RELATIONS Frequency- magnitude Relation Log 10 N = a – bM Aftershock Attenuation (p-value) N(t)  t -p Fractal Dimension

13. b - VALUE ESTIMATION 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 =log 10 e/M-M 0

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

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

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

17. Examples of Fractal Shapes Examples of Euclidean Shapes

18. Example of Correlation integral versus distance plot Fractal Dimension D 2 = 1.56

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

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

21. Normal fault RegimeThrust 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 )