EARTHQUAKE MAGNITUDE, INTENSITY, ENERGY, POWER LAW RELATIONS AND

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EARTHQUAKE MAGNITUDE, INTENSITY, ENERGY, POWER
LAW RELATIONS AND SOURCE MECHANISM
J R Kayal Geological Survey of India Kolkata e-mai
l jr_kayal_at_hotmail.com
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EARTHQUAKE CLASSIFICATION MAGNITUDE CLASSIFICAT
ION M 8.0 Great Earthquake 7.0 M lt
8.0 Major / Large Earthquake 5.0 M lt 7.0
Moderate Earthquake 3.0 M lt 5.0 Small
Earthquake 1.0 M lt 3.0 Microearthquake M
lt 1.0 Ultra Microearthquake
Hagiwara, 1964
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• NATURE OF EARTHQUAKES
• Foreshocks
• Main shock
• Aftershocks
• Earthquake Swarm
• Normal Seismic activity

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• TYPES OF EARTHQUAKES
• Tectonic Earthquake
• Volcanic Earthquake
• Collapse Earthquake
• Explosion Earthquake

CLASSIFICATION DISTANCE 1) Teleseismic
Earthquake gt 1000 km 2) Regional Earthquake gt
500 km 3) Local Earthquake lt 500 km
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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
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Richter Magnitude Scale
Distance S P Magnitude
Amplitude km sec
ML mm
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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.
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Isoseismal of the 2001 Bhuj Earthquake, Mw 7.7
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Isoseismals of large earthquakes in India
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INTENSITY AND ACCELERATION
log a 2 or a100 cm/sec2 0.1g, when I 7
and
a 1g , when I 10
Richter, 1958
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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
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POWER LAW RELATIONS
Frequency- magnitude Relation
Log10N a bM
Aftershock Attenuation (p-value)
N(t) ? t -p
Fractal Dimension
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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
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b-value

b 0.77
Log N
Magnitude
An example showing frequency-magnitude relation
in NE India
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b-value Map
Contour Map showing the variation of
b-value in NE India
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p-value
p 0.91
Log-Log Plot of no. of aftershocks with time
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Examples of Fractal Shapes
Examples of Euclidean Shapes
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Fractal Dimension
D2 1.56

Example of Correlation
integral versus distance plot
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Fractal Map
Contour Map showing variation of Fractal
Dimension in NE India
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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
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Normal fault Regime
Thrust fault Regime
Strike-slip fault Regime
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Fault Dimension
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Different Types of Faulting
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Graben Horst in Fault System
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Stress System
Fracture Criteria Mohr Circle
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Dynamics of Faulting
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Elastic Rebound Theory
Reid, 1910
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Plotting of P-wave First-motion (Equal Area
Projection)
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Equal Area Plot of a Plane and its Pole
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P-wave first-motion plot and fault plane solution
Kayal, 1984
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Source mechanisms of earthquakes at spreading
centre
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Source mechanisms of earthquakes at the
subduction zone, Indo-Burma ranges
Rao Kalpana, 2005
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Source mechanisms of earthquakes at the
Himalayan collision zone
Ni Barazangi, 1984
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Source mechanisms of intraplate earthquakes,
peninsular India
Kayal, 2000
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( Kayal 2000, JGS )
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( Kayal, 2000 JGS )
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(a) Fault-plane solutions of the Bhuj earthquakes
(b) N-S depth section of the earthquakes
(Kayal et al. 2002, JGS )
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Seismotectonic Model of 26th January, 2001 Bhuj
Earthquake
(Kayal et al. 2002, JGS )
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Thank you