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

EARTHQUAKE MAGNITUDE, INTENSITY, ENERGY, POWER LAW RELATIONS AND SOURCE MECHANISM. Walter D. Mooney U.S. Geological Survey California, USA e-mail: mooney @ usgs.gov. EARTHQUAKE CLASSIFICATION MAGNITUDE CLASSIFICATION M ≥ 8.0 Great 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 Walter D. Mooney U.S. Geological Survey California, USA e-mail: mooney @ usgs.gov

  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. 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

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

  10. 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

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

  12. 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

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

  14. Fault Dimension

  15. Different Types of Faulting

  16. Graben & Horst in Fault System

  17. Dynamics of Faulting

  18. Elastic Rebound Theory Reid, 1910

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

  20. Equal Area Plot of a Plane and its Pole

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

  22. Source mechanisms of earthquakes at spreading centre

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

  24. Thank you

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