earthquake magnitude, intensity, energy, power law relations and source mechanism walter d. mooney...

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