An earthquake is the resultof a sudden release of energy in the Earth's crust that creates seismic waves. The seismicity or seismic activity of an area refers to the frequency, type and size of earthquakes experienced over aperiod of time. Earthquakes are measured with a seismometer; a device which also records is known as seismograph.
EARTHQUAKE FAULT TYPES:
There are three main types of fault that may cause anearthquake: normal, reverse and strike-slip. Normal and reverse faulting are examples of dip-slip, where the displacement along the fault is in the direction of dip and movement on them involves avertical component. Normal faults occur mainly in areas where the crust is being extended such as a divergent boundary. Reverse faults occur in areas where the crust is being shortened such as at aconvergent boundary. Strike-slip faults are steep structures where the two sides of the fault slip horizontally past each other ; transform boundaries are a particular type of strike-slip fault. Manyearthquakes are caused by movement on faults that have components of both dip-slip and strike-slip; this is known as oblique slip.
EARTHQUAKES AWAY FROM PLATE BOUNDARIES:
Where plate boundariesoccur within continental lithosphere, deformation is spread out over a much larger area than the plate boundary itself. In the case of the fault continental transform, many earthquakes occur away fromthe plate boundary and are related to strains developed within the broader zone of deformation caused by major irregularities in the fault trace. The Northridge earthquake was associated with movementon a blind thrust within such a zone. Another example is the strongly oblique convergent plate boundary between the Arabian and Eurasian plates where it runs through the northwestern part of...