Skip to main content

Earthquake. Terminology and Concept

Earthquake

It is a transient violent movement of the Earth's surface that follows a release of energy in the Earth's crust.


2. Magnitude

It is a measure of the amount of energy released during an earthquake and expressed by Richter scale.


Effect of earthquake according to Richter scale.

Richter Magnitude Earthquake effects

Less than 3.5 Generally not felt, but recorded.

3.5-5.4 Often felt, but rarely causes damage.

Under 6.0 At most, slight damage to well-designed buildings. Can cause major damage to poorly constructed buildings over small regions.

6.1-6.9 Can be destructive in areas up to about 100 across where people live.

7.0-7.9 Major earthquake. Can cause serious damage over larger areas.

8 or greater Great Earthquake. Can cause serious damage in areas several hundred across.

3. Intensity

Intensity is a qualitative measure of the actual shaking at a location during an Earthquake, and is assigned in Roman Capital Numerical. It refers to the effects of earthquakes. Modified Mercalli scale is the standard measurement.


The intensity scale is based on the features of shaking, perception by people and animals, performance of buildings, and changes to natural surroundings.


Effects of earthquake based on its intensity

Intensity. Earthquake effects

I People do not feel any Earth movement

II A few people might notice movement if they are at rest and/or on the upper floors of tall buildings

III Many people indoors feel the movement. Hanging objects swing back and forth. People outdoors might not realize that an earthquake is occurring

IV Again, most people indoors feel the movement. The earthquake feels like a heavy truck hitting the walls. A few people outdoors may feel the movement as well.

V Almost everyone feels the movement. Sleeping people are awakened. Doors swing open or close. Dishes are broken. Trees might shake.

VI Everyone feels the movement. People have trouble walking. Objects fall from shelves. Damage is slight in poorly built buildings. No structural damage.

VII People have difficulty standing. Drivers feel their cars shaking. Some furniture breaks. Loose bricks fall from buildings.

VIII Drivers have trouble steering. Tall structures such as chimneys might twist and fall. Well-built buildings suffer slight damage. Poorly built structures suffer severe damage.

IX Well-built buildings suffer considerable damage. Some underground pipes are broken. The ground cracks. Reservoirs suffer serious damage.

X Most buildings and their foundations are destroyed. Some bridges are destroyed. Dams are seriously damaged. Large landslides occur. The ground cracks in large areas. Railroad tracks are bent slightly.

XI Most buildings collapse. Some bridges are destroyed. Large cracks appear in the ground. Underground pipelines are destroyed. Railroad tracks are badly bent.

XII Almost everything is destroyed. Objects are thrown into the air. The ground moves in waves or ripples. Large amounts of rock may move.


4. Focus or hypocenter

It is the point within the earth where an earthquake rupture starts


5. Epicenter

It is the point on the earth's surface vertically above the hypocenter, point in the crust.


6. Body waves

They move through the interior of the earth, as opposed to surface waves that ravel near the earth's surface.


6.1 P wave

A P wave, or compressional wave, the ground back and forth in the same direction and the opposite direction in the direction the wave is moving.


6.2 S wave

An S wave, or shear wave, shakes the ground back and forth perpendicular to the direction the wave is moving. S wave can travel only through solids.


7. Shallow Focus Earthquake

Earthquakes of focus less than 70 km deep from ground surface are called shallow focus earthquakes.


8. Teleseism

A teleseism is an earthquake recorded by a seismograph at a distance. By international convention the distance is over 1000 Kilometers from the epicenter.


 9. Microseism

These are more or less continuous disturbances in the ground recorded by seismographs.


10. Micro earthquake

A very small earthquake having a magnitude measurable less than three on scale is called a Micro-earthquake.


11. Accelerogram

The ground acceleration record produced by Accelerograph is called Accelerogram.


12. Accelerograph

This is an earthquake-recording device designed to measure the ground motion in terms of acceleration in the epicentral region of strong shaking.


13. Focal distance

The straight-line distance between the places of recording/observation to the hypocenter is called the focal distance.


14. Intermediate Focus Earthquake

When the focus of an Earthquake is between 70 to 300 km deep it is termed as Intermediate Focus Earthquake.


15. Epicentral Distance

Distance between epicenter and recording station(in km) is termed as Epicentral Distance.


16. Foreshocks

Smaller earthquakes preceding the main earthquake results in the generation of Foreshocks.


17. Aftershocks

Smaller earthquakes following the main earthquake results in the development of aftershocks.


18. Benioff zone

A region of earthquake activity inclined at an angle underneath a destructive boundary.


19. Destructive boundary

A part of the earth's crust where tectonic plates move towards one another, resulting in the seduction of one below the other.


20. Fault

A fracture in the rocks along which strain is occasionally released as an earthquake.


21. Active fault

Faults considered to be active if they have moved one or more time in the 10000 years.


22. Liquefaction

The process by which sediments and soil collapse, behaving like a thick liquid when shaken by earthquake waves.


23. Magnitude/frequency relationship

The observed relationship (with most hazards) that bigger scale events occur less frequently while smaller scale events are relatively common.


24. Richter scale

A measure of earthquake magnitude allowing an estimate of energy levels involved.


25. Rossi-Forrel scale

An observational scale for measuring earthquake intensity. This was improved and expanded by Mercalli to produce the "Modified Mercalli Scale".


26. Seismometer

An instrument for detecting and recording earthquake waves.


27. Seismograph

A printout from a seismometer. Studies of seismograph traces can be used to pinpoint both the epicenter of an earthquake and the nature of the fault movement.


28. Tsunami

An earthquake generated sea wave. Can travel thousands of miles and reach many metres in height when approaching shallow water.


Comments

Post a Comment

Popular posts from this blog

History of GIS

1. 1832 - Early Spatial Analysis in Epidemiology:    - Charles Picquet creates a map in Paris detailing cholera deaths per 1,000 inhabitants.    - Utilizes halftone color gradients for visual representation. 2. 1854 - John Snow's Cholera Outbreak Analysis:    - Epidemiologist John Snow identifies cholera outbreak source in London using spatial analysis.    - Maps casualties' residences and nearby water sources to pinpoint the outbreak's origin. 3. Early 20th Century - Photozincography and Layered Mapping:    - Photozincography development allows maps to be split into layers for vegetation, water, etc.    - Introduction of layers, later a key feature in GIS, for separate printing plates. 4. Mid-20th Century - Computer Facilitation of Cartography:    - Waldo Tobler's 1959 publication details using computers for cartography.    - Computer hardware development, driven by nuclear weapon research, leads to broader mapping applications by early 1960s. 5. 1960 - Canada Geograph...
Post a Comment
Read more

Spectral Signature vs. Spectral Reflectance Curve

Spectral Signature  A spectral signature is the unique pattern in which an object: absorbs energy reflects energy emits energy across different wavelengths of the electromagnetic spectrum. ✔ Key Points Every natural and man-made object on Earth interacts with sunlight differently. These interactions produce a distinct pattern , just like a "fingerprint". Sensors on satellites record these patterns as digital numbers (DN values) . These patterns help to identify and differentiate objects such as vegetation, soil, water, snow, buildings, minerals, etc. ✔ Examples of Spectral Signatures Healthy vegetation → High reflectance in NIR , strong absorption in red Water → Strong absorption in NIR and SWIR , low reflectance Dry soil → Gradual increase in reflectance from visible to NIR Snow → High reflectance in visible , low in SWIR ✔ Why Spectral Signature Matters It allows: Land cover classification Chan...
Post a Comment
Read more

Platforms in Remote Sensing

In remote sensing, a platform is the physical structure or vehicle that carries a sensor (camera, scanner, radar, etc.) to observe and collect information about the Earth's surface. Platforms are classified mainly by their altitude and mobility : Ground-Based Platforms Definition : Sensors mounted on the Earth's surface or very close to it. Examples : Tripods, towers, ground vehicles, handheld instruments. Applications : Calibration and validation of satellite data Detailed local studies (e.g., soil properties, vegetation health, air quality) Strength : High spatial detail but limited coverage. Airborne Platforms Definition : Sensors carried by aircraft, balloons, or drones (UAVs). Altitude : A few hundred meters to ~20 km. Examples : Airplanes with multispectral scanners UAVs with high-resolution cameras or LiDAR High-altitude balloons (stratospheric platforms) Applications : Local-to-regional mapping ...
Post a Comment
Read more

Model GIS object attribute entity

These concepts explain different ways of organizing, storing, and representing geographic information in a Geographic Information System (GIS) . They include database design models (ER model), data structure models (Object and Attribute models), and spatio-temporal representations that integrate location, entities, and time . Together, they help GIS manage both spatial data (where things are) and descriptive information (what they are and how they change over time) . 1. Object-Based Model (Object-Oriented Data Model) The Object-Based Model treats geographic features as independent objects that combine spatial geometry and descriptive attributes within a single structure. Core Concept: Each geographic feature (such as a building, road, or river ) is represented as a self-contained object that stores both: Geometry – location and shape (point, line, polygon) Attributes – descriptive properties (name, type, length, capacity) Unlike older georelational models , which stored spatial ...
Post a Comment
Read more

GIS data continuous discrete ordinal interval ratio

In Geographic Information Systems (GIS) , data is categorized based on its nature (discrete or continuous) and its measurement scale (nominal, ordinal, interval, or ratio). These distinctions influence how the data is collected, analyzed, and visualized. Let's break down these categories with concepts, terminologies, and examples: 1. Discrete Data Discrete data is obtained by counting distinct items or entities. Values are finite and cannot be infinitely subdivided. Characteristics : Represent distinct objects or occurrences. Commonly represented as vector data (points, lines, polygons). Values within a range are whole numbers or categories. Examples : Number of People : Counting individuals on a train or in a hospital. Building Types : Categorizing buildings as residential, commercial, or industrial. Tree Count : Number of trees in a specific area. 2. Continuous Data Continuous data is obtained by measuring phenomena that can take any value within a range...
Post a Comment
Read more