(I) - Not felt except by a very few under especially favourable conditions.
(II) - Felt only by a few persons at rest, especially on upper floors of buildings. Delicately suspended objects may swing.
(III) - Felt quite noticeably by persons indoors, especially on the upper floors of buildings. Many do not recognize it as an earthquake. Standing motor cars may rock slightly. Vibration similar to the passing of a truck. Duration estimated.
(IV) - Felt indoors by many, outdoors by few during the day. At night, some awakened. Dishes, windows, doors disturbed; walls make cracking sound. Sensation like heavy truck striking building. Standing motor cars rocked noticeably.
(V) - Felt by nearly everyone; many awakened. Some dishes and windows broken. Unstable objects overturned. Clocks may stop.
(VI) - Felt by all; many frightened and run outdoors, walk unsteadily. Windows, dishes, glassware broken... books off shelves... some heavy furniture moved or overturned; a few instances of fallen plaster. Damage slight.
(VII) - Difficult to stand... furniture broken..damage negligible in building of good design and construction; slight to moderate in well-built ordinary structures; considerable damage in poorly built or badly designed structures; some chimneys broken. Noticed by persons driving motor cars
(VIII) - Damage slight in specially designed structures; considerable in ordinary substantial buildings with partial collapse. Damage great in poorly built structures. Fall of chimneys, factory stacks, columns, monuments, walls. Heavy furniture moved.
(IX) - General panic... damage considerable in specially designed structures, well designed frame structures thrown out of plumb. Damage great in substantial buildings, with partial collapse. Buildings shifted off foundations
(X) - Some well built wooden structures destroyed; most masonry and frame structures destroyed with foundation. Rails bent.
(XI) - Few, if any masonry structures remain standing. Bridges destroyed. Rails bent greatly.
(XII) - Damage total. Lines of sight and level distorted. Objects thrown into the air.
Magnitude Frequency Per Year Great 8.0 + 1 Major 7 -7.9 18 Large 6-6.9 120 Moderate 5-5.9 1000 Minor 4-4.9 6,000 Generally Felt 3-3.9 49,000 Potentially Perceptible 2 – 2.9 300,00 Inperceptible less than 2 600,000+
SEISMIC WAVES The energy released by an earthquake travels through the earth. The speed of a seismic waves depends on the density and elasticity of the material through which they travel.
TYPES OF SEISMIC WAVES Body waves Surface waves P -WAVES S – WAVES R -WAVES L – WAVES
BODY WAVES Speed decreases with increasing density of rock and increases with rock elasticity
P –WAVES (PRIMARY WAVES) Compressional waves that vibrate parallel to the direction of wave movement. Travels through all medium. Fastest seismic waves.
S – WAVES (Secondary waves) Also known as shear waves. Vibrate perpendicular to the direction of wave movement. Travel only on solid.
Kobe Earthquake In January 1995 a road connecting Kôbe with Osaka collapsed during the most deadly earthquake to hit Japan since 1923. The quake ignited firestorms and caused massive destruction in Kôbe. In all, more than 5,000 people were killed and hundreds of thousands were left homeless .
Alaskan Earthquake The Alaskan earthquake of 1964 was rated 9.2 on the Richter scale. One of the most powerful earthquakes ever known to hit North America, it claimed 131 lives and devastated parts of Anchorage and Valdez. The quake destroyed foundations and left gaping cracks in the cement of this street.
Seismic Zones There are five seismic zones named as I to V as details given below:- Zone V : Covers the areas liable to seismic intensity IX and above on Modified Mercalli Intensity Scale. This is the most severe seismic zone and is referred here as Very High Damage Risk Zone. Zone IV : Gives the area liable to MM VIII. This, zone is second in severity to zone V. This is referred here as High Damage Risk Zone. Zone III : The associated intensity is MM VII. This is termed here as Moderate Damage Risk Zone. Zone II : The probable intensity is MM VI. This zone is referred to as Low Damage Risk Zone. Zone I : Here the maximum intensity is estimated as MM V or less. This zone is termed here as Very Low Damage Risk Zone
Global Positioning System (GPS): A system of Earth-orbiting satellites, each providing precise time and position information which enables GPS receiving devices to compute positions on the Earth. Signals must be received from at least three satellites in order to establish the receiver’s position in latitude and longitude, or according to a national coordinate system provided by the equipment. Measurements from a fourth satellite are required to calculate altitude (height) position.
It is a Japanese term which means “wave in port” or “Harbour Wave” Tsunami’s are high speed giant size sea waves caused due to increasing energy as the waves caused by a deep sea earthquake
Rupture in seafloor pushes water upwards starting the wave Wave moves rapidly in deep ocean reaching speed up to 500km/h Wave heads inland destroying all its path As the wave nears land it Slows up to 45km/h But is squeezed upwards increasing in height
Deep oceanic Assessment and Reporting of Tsunamis (DART) Following an under water earthquake pressure sensor placed on the ocean bed pick up the signals and transmit them to floating buoys on the sea, which in turn beam them to satellite for transmit them to warning centre.