Earthquakes: Processes, Instrumentation, Geography, and Effects

Vocabulary flashcards covering earthquake distributions, instrumentation, scales, causes, and destructive/constructive effects based on the provided lecture transcript.

Circum-Pacific Earthquake Belt

The earthquake belt surrounding the Pacific Ocean—including Alaska, the Aleutian Islands, Japan, the Philippines, New Zealand, and the coasts of North and South America—that accounts for $68\%$ of all earthquakes in the world.

Mid-World Mountain Earthquake Belt

The earthquake belt extending from the Alps through Turkey, Iran, Iraq, the Himalayas, and into China, accounting for about $31\%$ of the world's earthquakes.

Focus (Hypocentre)

The point within the Earth where tension is released, leading to the occurrence of an earthquake and the outward propagation of vibrating waves.

Epicentre

The point on the surface of the Earth located directly above the earthquake's focus (hypocentre), where the greatest damage usually occurs.

Seismology

The scientific study of earthquakes and the propagation of elastic waves through the Earth.

Seismologist

A geophysicist who studies earthquakes and the mechanical characteristics of the Earth.

Seismometer

An instrument that measures the intensity of seismic activities.

Seismograph

An instrument containing a suspended mass that records earthquake waves on graph paper (producing a seismogram).

Seismoscope

An instrument that indicates seismic activity that has already occurred and provides information about its magnitude.

Richter Scale

A magnitude scale invented in $1935$ by American seismologist Charles Francis Richter ranging between $0$ and $9$.

Mercalli Scale

An intensity scale introduced in the twentieth century by Italian seismologist Giuseppe Mercalli, with gradations measuring vibrations from $\text{I}$ to $\text{XII}$.

Moment Magnitude Scale (MMS)

A scale developed in the $1970\text{s}$ by the US Geological Survey to calculate the magnitude of large earthquakes.

Faulting

The breaking and displacement of rocks along a line of weakness inside the Earth caused by accumulated tension and stress.

San Andreas Fault

A major fault line in California, USA, created by crustal cracking, which serves as the chief cause of earthquakes in California.

Krakatoa Eruption (1883)

A violent volcanic eruption in $1883$ caused by a temporarily plugged vent, which resulted in a violent earthquake.

Nepal Earthquake (25 April 2015)

A severe earthquake resulting from the subduction of the Indian Plate under the Eurasian Plate during their tectonic collision.

Salvador Earthquake (2001)

An earthquake occurring in $2001$ triggered by a massive landslide, causing hundreds of deaths.

Soil Liquefaction

A process during earthquake tremors in which water-saturated granular materials (such as sand) lose strength and temporarily transform from a solid to a liquid state.

Tsunami

Massive sea waves generated by seabed earthquakes that can reach heights of $20-25\,m$, such as the December 2004 Sumatra tsunami that caused around three lakh deaths.

Geysers and Hot Springs

Constructive features formed when earthquakes create cracks/fissures through which superheated steam and sulphur-rich water reach the surface from underground volcanic regions.