Science | Arkin

• Fault is a planar fracture or discontinuity in a volume of rock, across which there has been significant displacement as a result of rock-mass movement.
• Faults form as the Earth's crust deforms due to stress.
• Foot wall is the block of rock that lies on the underside of an inclined fault or of a mineral deposit.
• Hanging wall is the block of rock that lies above an inclined fault.
• A fault plane is the plane, or surface formed between the two rock blocks that slip one with the other during an earthquake.
• A fault scarp is a feature on the surface of the earth that looks like a step caused by a slip on the fault.
• A fault line is a break or fracture in the ground that occurs when the Earth's tectonic plates move or shift, and these are areas where earthquakes are likely to occur.
• Stress is a force that acts on an area of rock to change its shape or volume.
• Tension stress pulls and stretches rock so that it becomes thinner in the middle.
• Compression stress squeezes rock together until it folds or break.
• Shearing stress pushes masses of rock in opposite directions in sideways movement.
• Normal faults occur when two blocks of rock are pulled apart, as by tension. The hanging wall goes downward.
• Reverse fault occur when two blocks of rock are forced together by compression. The hanging wall moves upward and fault is steep.
• Strike-Slip/Transform Fault are vertical (or nearly vertical) fractures where the blocks have mostly moved horizontally.
• Divergent is a plate boundary where two plates move away from each other.
• Convergent is a plate boundary where two plates move towards each other.
• Transform is a plate boundary where two plates move past each other in opposite directions.
• Sinistral is when the far side moves to the left.
• Dextral is when the far side moves to the right.
• Subduction is the process that occurs when two tectonic plates meet at convergent boundaries and one of the plates moves under the other due to gravity and differences in density. Over time they create volcanoes and mountains.
• Trenches are long, narrow depressions on the seafloor that form at the boundary of tectonic plates where one plate is pushed, or subducts, beneath another.
• Rifting is defined as the splitting apart of a single tectonic plate into two or more tectonic plates separated by divergent plate boundaries.
• A ridge is a long, narrow, elevated geomorphologic landform, structural feature, or a combination of both separated from the surrounding terrain by steep sides.
• Syncline is a fold with youthful layers nearer to the core of the structure.
• Anticline is a fold that is convex upward, while syncline is a fold that is concave upward.
• Limbs are the two sides of the fold.
• An earthquake is a weak to violent shaking of the ground produced by the sudden movement of rock materials below the earth's surface.
• The epicenter is the point on the ground directly above the focus.
• Fault is the weak point in the tectonic plate where pressure within the crust is released.
• Seismic waves are waves that transmit energy released by an earthquake.
• Focus is where the earthquake begins.
• Tectonic earthquakes are caused by the movement of the Earth's plates. The energy released during these earthquakes is incredibly powerful and can cause extensive damage.
• Volcanic earthquakes are caused by the movement of magma beneath the Earth's surface. These earthquakes are often smaller than tectonic earthquakes, but they can still cause significant damage.
• Collapse earthquakes occur when buildings or other structures collapse. These earthquakes are typically very small but can be deadly if they occur in a populated area.
• Explosion earthquakes are caused by the detonation of explosives. These earthquakes are usually very small but can cause damage if they occur near populated areas.
• Magnitude measures the amount of energy released at the source of an earthquake. It is determined from measurement on seismographs. It is represented by Hindu Arabic Numbers (e.g. 2.0, 4.5, 7.8) on the Richter Scale.
• Intensity measures how strong the shaking generated by the earthquake as perceived and felt by people in a certain locality or the degree of damage it caused in the area. The intensity is generally higher near the epicenter. It is represented by Roman Numerals (e.g. II, IV, IX) determined by the Mercalli Scale.
• Seismology is the study of earthquakes.
• Seismologist is the scientist who studies earthquakes.
• A seismograph is an instrument used to record earthquake waves (seismic waves). It measures the strength and the size of an earthquake by means of magnitude and intensity.