EARTHQUAKE MAGNITUDE, INTENSITY, EARTHQUAKE MAGNITUDE, INTENSITY,
ENERGY, POWER LAW RELATIONS AND ENERGY, POWER LAW RELATIONS AND
SOURCE MECHANISMSOURCE MECHANISM
Walter D. MooneyU.S. Geological Survey
California, USAe-mail: mooney @ usgs.gov
EARTHQUAKE CLASSIFICATIONEARTHQUAKE 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
NATURE OF EARTHQUAKESNATURE OF EARTHQUAKES
1) Foreshocks
2) Main shock
3) Aftershocks
4) Earthquake Swarm
5) Normal Seismic activity
CLASSIFICATION DISTANCE
1) Teleseismic Earthquake > 1000 km
2) Regional Earthquake > 500 km
3) Local Earthquake < 500 km
TYPES OF EARTHQUAKESTYPES OF EARTHQUAKES
1) Tectonic Earthquake
2) Volcanic Earthquake
3) Collapse Earthquake
4) Explosion Earthquake
EARTHQUAKE MAGNITUDEEARTHQUAKE MAGNITUDE
Richter Magnitude ML (Local Magnitude)
ML = log A - log Ao ( )
Body-wave Magnitude (mb)
mb = log (A/T) - f (,h)
Surface-wave Magnitude (Ms)
Ms= log AHmax - log Ao (o)
MS = log (A/T)max + 1.66 log + 3.3
Moment Magnitude (Mw)Mw = 2/3 log Mo - 10.7 Mo = A u
Duration Magnitude (MD)
MD = - 0.87 + 2.00 log + 0.0035
Macroseismic Magnitude (Mms)Mms = 0.5Io + log h + 0.35
Richter Magnitude Scale
Distance S – P Magnitude Amplitude km sec ML mm
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.
EARTHQUAKE ENERGYEARTHQUAKE ENERGY
log E = 12 + 1.8 ML
log E = 5.8 + 2.4 mb
log E = 11.4 + 1.5 Ms
1.0 10.0 times about 32 times0.5 3.2 times about 5.5 times0.3 2.0 times about 3 times0.1 1.3 times about 1.4 times
Magnitude Ground Motion Magnitude Ground Motion Energy Energy
Magnitude versus ground motion and energy
POWER LAW RELATIONSPOWER LAW RELATIONS
Frequency- magnitude Relation
Log10N = a – bM
Aftershock Attenuation (p-value)
N(t) t -p
Fractal Dimension2~)( DrrC
b - VALUE ESTIMATIONb - 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
b = 0.77
Magnitude
Log
N
An example showing frequency-magnitude relation in NE India
b-value:
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
Normal fault Regime Thrust fault Regime
Strike-slip fault Regime
4 CHAPTER FIG. 1
Foot wall
hd
55°
35° Hanging wall
Fault Dimension
Different Types of Faulting
Graben & Horst in Fault System
Dynamics of FaultingDynamics of Faulting
Elastic Rebound TheoryElastic Rebound Theory
Reid, 1910
Plotting of P-wave First-motion(Equal Area Projection)
Equal Area Plot of a Plane and its Pole
P-wave first-motion plot and fault plane solution
Kayal, 1984
Source mechanisms of earthquakes at spreading centre
Source mechanisms of earthquakes at the subduction zone, Indo-Burma ranges
Rao & Kalpana, 2005
