Seismic zones in India


India being a huge landmass is especially inclined to seismic tremors. The Indian subcontinent is separated into five seismic zones concerning the seriousness of the quakes. The order of the zones has been finished by the geologist and researcher as right on time as 1956 when a 3-zone (Severe, Light and Minor danger) Seismic Zoning Map of India was delivered. From that point forward the issue of seismic risk has been tended to by various specialists and offices

The previously mentioned guide depended on a wide idea of seismic quake dissemination and geotectonics. The serious peril zones are generally restricted to plate limit districts, ie, the Himalayan frontal circular segment in the North, the chaman fault area in the north west and the Indo-Burma region in the north east. The lower danger zone is kept to indian shield in the south and average  peril zone limited to the transitional zone in the middle of the two.

The bureau of Indian standards is the official office for distributing the seismic risk maps and codes. It has brought out variants of seismic zoning map: a six zone outline 1962, a seven zone delineate 1966, and a five zone delineate/1984. The remainder of these maps is as of now legitimate; this guide was made in view of the estimations of greatest MM powers recorded in different parts of the nation, in noteworthy circumstances.

Zone V is the most defenseless against earthquake, where generally a portion of the nation’s most effective stun have happened. This locale incorporated the Andaman and Nicobar Islands, all of North-Eastern India, parts of north-western Bihar, eastern areas of Uttaranchal, the Kangra Valley in Himachal Pradesh, close to the Srinagar region in Jammu and Kashmir and the Rann of Kutchh in Gujarat. Seismic earthquake with extents in overabundance of 7.0 have occured in these territories, and have had forces higher than IX.

Quite a bit of India lies in Zone III, where a most extreme power of VII can be normal. Four of the real metropolitan zones lie in Zone IV, i.e. New Delhi, Mumbai and Calcutta. Just Chennai lies in Zone II. A substantial area of south-focal India lies in Zone I alongside a segment extending from eastern Rajasthan into northern Madhya Pradesh. A few ranges of Orissa, Jharkhand and Chhatisgarh additionally lie in Zone I.

Lately India has been a host to numerous seismic earthquake of shifting extent and force. The accompanying table gives a point by point order.

33TE EPICENTER

 

Lat(Deg N)      Long(Deg E)

LOCATION MAGNITUDE
1819 June 16   23.6                    68.6 KUTCH, GUJARAT 8.0
1869 JAN 10   25                        93 NEAR CACHAR, ASSAM 7.5
1885 MAY 30   34.1                    74.6 SOPOR, J&K 7.0
1897 JUN 12   26                        91 SHILLONG PLATEAU 8.7
1905 APR 04   32.3                    76.3 KANGRA, H.P 8.0
1918 JUL 08   24.5                    91.0 SRIMANGAL, ASSAM 7.6
33TE EPICENTER

 

Lat(Deg N)      Long(Deg E)

LOCATION MAGNITUDE
1819 June 16   23.6                    68.6 KUTCH, GUJARAT 8.0
1869 JAN 10   25                        93 NEAR CACHAR, ASSAM 7.5
1885 MAY 30   34.1                    74.6 SOPOR, J&K 7.0
1897 JUN 12   26                        91 SHILLONG PLATEAU 8.7
1905 APR 04   32.3                    76.3 KANGRA, H.P 8.0
1918 JUL 08   24.5                    91.0 SRIMANGAL, ASSAM 7.6
1930 JUL 02   25.8                    90.2 DHUBRI, ASSAM 7.1
1934 JAN 15   26.6                    86.8 BIHAR-NEPAL BORDER 8.3
1941 JUN 26   12.4                    92.5 ANDAMAN ISLANDS 8.1
1943 OCT 23   26.8                    94.0 ASSAM 7.4
1950 AUG 15   28.5                    96.7 ARUNACHAL PRADESH-CHINA BORDER 8.5
1956 JUL 21   23.3                    70.0 ANJAR, GUJARAT 7.0
1967 DEC 10   17.37                    73.75 KOYNA, MAHARASHTRA 6.5
1975 JAN 19   32.38                    78.49 KINNAUR, HP 6.2
1988 AUG 06   25.13                    95.15 MANIPUR-MYANMAR BORDER 6.6
1988 AUG 21   26.72                    86.63 BIHAR-NEPAL BORDER 6.4
1991 OCT 20   30.75                    78.86 UTTARKASHI, UP HILLS 6.6
1993 SEP 30   18.07                    76.62 LATUR-OSMANABAD, MAHARASHTRA 6.3
1997 MAY 22   23.08                    80.06 JABALPUR,MP 6.0
1999 MAR 29   30.41                    79.42 CHAMOLI DIST, UP 6.8

Richter Scale

Seismic waves are the vibrations from quakes that go through the Earth; they are recorded on instruments called seismographs. Seismographs record a crisscross trace that demonstrates the changing amplitude of ground motions underneath the instrument. Delicate seismographs, which significantly amplify these ground movements, can recognize solid quakes from sources anyplace on the planet. The time, areas, and size of a quake can be resolved from the information recorded by seismograph stations. The Richter extent scale was produced in 1935 by Charles F. Richter of the California Institute of Technology as a scientific gadget to think about the extent of seismic tremors. The size of a tremor is resolved from the logarithm of the abundance of waves recorded by seismographs. Changes are incorporated for the variety out there between the different seismographs and the epicenter of the quakes. On the Richter scale, size is communicated in entire numbers and decimal parts. For instance, a size 5.3 may be registered for a direct tremor, and a solid quake may be evaluated as greatness 6.3. In view of the logarithmic premise of the scale, every number increment in size speaks to a ten times increment in measured plentiful-ness; as a gauge of vitality, every entire number stride in the extent scale relates to the arrival of around 31 times more vitality than the sum connected with the previous entire number esteem Earthquakes with size of around 2.0 or less are typically call miniaturized scale tremors; they are not regularly felt by individuals and are by and large recorded just on nearby seismographs. Occasions with sizes of around 4.5 or more noteworthy – there are a few thousand such stuns every year –are sufficiently solid to be recorded by delicate seismographs everywhere throughout the world. Awesome quakes, for example, the 1964 Good Friday seismic tremor in Alaska, have sizes of 8.0 or higher. On the normal, one seismic tremor of such size happens some place on the planet every year. Despite the fact that the Richter Scale has no maximum farthest point, the biggest known stuns have had extents in the 8.8 to 8.9 territory. As of late, another scale called the minute greatness scale has been concocted for more exact investigation of extraordinary tremors. The Richter Scale is not used to express harm. A quake in a thickly populated zone which brings about numerous passing and striking harm may have an ample damage from same magnitude in a remote region that does just scare the untamed life. Substantial magnitude earthquakes and  seismic tremors that happen underneath the seas may not be felt by people.

SEISMIC ACTIVE ZONE:

The design of a seismic resistant building includes utilization of seismic coefficients. For the objective of manipulating these coefficients the country is separated into FIVE zones ( as recommended in IS 1897 – 1984)

ZONE 1 Area without any damage

ZONE 2 Area with major damage ( i.e., causing damages to structures with fundamentally periods greater than 1.0 second ) earthquakes corresponding to intensities V to VI of MM scale ( MM – Modified Mercalli Intensity scale )

ZONE 3 Moderate damage equivalent to intensity VII of MM scale

ZONE 4 Major damage equivalent to intensity VII and higher of MM scale.

ZONE 5 Area determined by pro seismically of specific major fault systems.