Causes and Types of Earthquakes

• Earthquakes are natural events resulting from the sudden release of energy in the Earth's crust.

Causes of Earthquakes

• Tectonic plate movement refers to the motion of large sections of the Earth's lithosphere (tectonic plates) over the semi-fluid asthenosphere, driven by heat from the Earth's core, causing convection currents in the mantle.
• Earthquakes can be triggered by volcanic activity, fracturing surrounding rocks.
• Volcanic earthquakes are also referred to as volcanic-tectonic earthquakes
• Human activities like mining, reservoir-induced seismicity (from filling large reservoirs behind dams), and hydraulic fracturing (fracking) can cause earthquakes.

Types of Plate Boundaries

• Convergent boundaries involve two plates colliding or moving towards each other, potentially leading to subduction.
• Divergent boundaries occur where plates move apart, creating tension and cracks, and can lead to earthquakes along faults.
• Transform boundaries where plates slide past each other horizontally, can release stress and cause earthquakes.

Faulting and its Role in Earthquakes

• Faulting is a geological process where Earth's crust breaks and shifts due to accumulated stress.
• A fault is a fracture or zone of fractures between two blocks of rock, allowing relative movement.

Types of Faults

• Normal faults happen when the Earth's crust is extended or pulled apart, causing the hanging wall to move downward relative to the footwall.
• Reverse (thrust) faults occur when the crust is compressed, causing the hanging wall to move upward relative to the footwall.
• Strike-slip faults are primarily horizontal with little vertical displacement, move laterally, typically at transform plate boundaries.

Two Types of Strike Shift Fault

• Left lateral fault
• Right lateral fault
• Some regions have multiple interconnected faults, known as fault zones.