An earthquake is a phenomenon that occurs without warning and involves violent shaking of the ground and everything over it. It results from the release of accumulated stress of the moving lithospheric or crustal plates. The earth's crust is divided into seven major plates, that are about 50 miles thick, which move slowly and continuously over the earth's interior and several minor plates. Earthquakes are tectonic in origin; that is the moving plates are responsible for the occurrence of violent shakes. The occurrence of an earthquake in a populated area may cause numerous casualties and injuries as well as extensive damage to property.
The Earthquake Risk in India
India's increasing population and extensive unscientific constructions mushrooming all over, including multistoried luxury apartments, huge factory buildings, gigantic malls, supermarkets as well as warehouses and masonry buildings keep - India at high risk. During the last 15 years, the country has experienced 10 major earthquakes that have resulted in over 20,000 deaths. As per the current seismic zone map of the country (IS 1893: 2002), over 59 per cent of India’s land area is under threat of moderate to severe seismic hazard-; that means it is prone to shaking of MSK Intensity VII and above (BMTPC, 2006). In fact, the entire Himalayan belt is considered prone to great earthquakes of magnitude exceeding 8.0-; and in a relatively short span of about 50 years, four such earthquakes have occurred: 1897 Shillong (M8.7); 1905 Kangra (M8.0); 1934 Bihar-Nepal (M8.3); and 1950 Assam-Tibet (M8.6). Scientific publications have warned of the likelihood of the occurrence of very severe earthquakes in the Himalayan region, which could adversely affect the lives of several million people in India.
At one time regions of the country away from the Himalayas and other inter-plate boundaries were considered to be relatively safe from damaging earthquakes. However, in the recent past, even these areas have experienced devastating earthquakes, albeit of lower magnitude than the Himalayan earthquakes. The Koyna earthquake in 1967 led to revision of the seismic zoning map, resulting in deletion of the non-seismic zone from the map. The areas surrounding Koyna were also re-designated to Seismic Zone IV, indicating high hazard. The occurrence of the Killari earthquake in 1993 resulted in further revision of the seismic zoning map in which the low hazard zone or Seismic Zone I was merged with Seismic Zone II, and some parts of Deccan and Peninsular India were brought under Seismic Zone III consisting of areas designated as moderate hazard zone areas. Recent research suggests that as understanding of the seismic hazard of these regions increases, more areas assigned as low hazard may be re-designated to higher level of seismic hazard, or vice-versa.
The North-Eastern part of the country continues to experience moderate to large earthquakes at frequent intervals including the two great earthquakes mentioned above. Since 1950, the region has experienced several moderate earthquakes. On an average, the region experiences an earthquake with a magnitude greater than 6.0 every year. The Andaman and Nicobar Islands are also situated on an inter-plate boundary and frequently experience damaging earthquakes.
The increase in earthquake risk is due to a spurt in developmental activities driven by urbanization, economic development and the globalization of India’s economy. The increase in use of high-technology equipment and tools in manufacturing and service industries has also made them susceptible to disruption due to relatively moderate ground shaking. As a result, loss of human life is not the only determinant of earthquake risk any more. Severe economic losses leading to the collapse of the local or regional economy after an earthquake may have long-term adverse consequences for the entire country. This effect would be further magnified if an earthquake affects a mega-city, such as Delhi or Mumbai.
What to Do After an Earthquake
- Keep calm, switch on the radio/TV and obey any instructions you hear on it.
- Keep away from beaches and low banks of rivers. Huge waves may sweep in.
- Be prepared to expect aftershocks.
- Turn off the water, gas and electricity.
- Do not smoke and do not light matches or use a cigarette lighter. Do not turn on switches. There may be gas leaks or short-circuits. Use a torch.
- If there is a fire, try to put it out. If you cannot, call the fire brigade.
- If people are seriously injured, do not move them unless they are in danger.
- Immediately clean up any inflammable products that may have spilled (alcohol, paint, etc).
- If you know that people have been buried, tell the rescue teams. Do not rush and do not worsen the situation of injured persons or your own situation.
- Avoid places where there are loose electric wires and do not touch any metal object in contact with them.
- Do not drink water from open containers without having examined it and filtered it through a sieve, a filter or an ordinary clean cloth.
- If your home is badly damaged, you will have to leave it. Collect water containers, food, and ordinary and special medicines (for persons with heart complaints, diabetes, etc.)
- Do not re-enter badly damaged buildings and do not go near damaged structures.
- Battery operated torch
- Extra batteries
- Battery operated radio
- First aid kit and manual
- Emergency food (dry items) and water (packed and sealed)
- Candles and matches in a waterproof container
- Chlorine tablets or powdered water purifiers
- Can opener.
- Essential medicines
- Cash, Aadhar Card and Ration Card
- Thick ropes and cords
- Sturdy shoes
Tetemeko la ardhi ni tukio linalotokea bila onyo na linahusisha kutetemeka kwa nguvu kwa ardhi na kila kitu kilicho juu yake. Ni matokeo ya kutolewa kwa mkazo uliokusanywa wa mabamba ya lithospheric au crustal yanayohama. Kwa mfano, dunia imegawanywa katika mabamba saba makubwa, yenye unene wa kilometa 50 hivi, ambayo yanaendelea kusonga polepole na kwa kuendelea juu ya sehemu ya ndani ya dunia, na mabamba madogo kadhaa. Matetemeko ya ardhi ni ya asili ya tectonic; yaani, mabamba yanayohamia ndiyo husababisha matetemeko makali. Matetemeko ya ardhi katika eneo lenye watu wengi yanaweza kusababisha majeruhi na majeraha mengi na vilevile uharibifu mkubwa wa mali. India ina idadi ya watu inayoongezeka na ujenzi mkubwa usio wa kisayansi unaongezeka kila mahali, ikiwa ni pamoja na vyumba vya kifahari vya ghorofa nyingi, majengo makubwa ya kiwanda, maduka makubwa, maduka makubwa na vile vile maghala na majengo ya mawe yanaendelea kuwa hatari. Katika miaka ya hivi karibuni, nchi hiyo imepatwa na matetemeko makubwa ya ardhi ambayo yamesababisha vifo vya watu zaidi ya 20,000. Kulingana na ramani ya eneo la tetemeko la ardhi (IS 1893: 2002), zaidi ya asilimia 59 ya eneo la ardhi la India liko chini ya tishio la hatari ya tetemeko la ardhi la wastani hadi kali, ambayo inamaanisha kuwa ina uwezekano wa kutetemeka kwa kiwango cha MSK 7 na zaidi. Kwa kweli, eneo lote la Himalaya linaonwa kuwa lina uwezekano wa kutetemeka kwa tetemeko kubwa la ardhi lenye ukubwa wa zaidi ya 8.0, na katika kipindi kifupi cha miaka 50 hivi, tetemeko hilo limetokea mara nne: Shillong (M8.7), Kangra (M8.0) mwaka wa 1905, Bihar-Nepal (M8.3) mwaka wa 1934, na Assam-Tibet (M8.6) mwaka wa 1950. "Mapokeo ya utafiti wa kisayansi yanaonyesha kwamba kuna uwezekano mkubwa wa kutokea kwa matetemeko makubwa ya ardhi katika eneo la Himalaya, ambayo yanaweza kuathiri maisha ya mamilioni ya watu nchini India.""" Wakati mmoja, maeneo ya nchi yaliyo mbali na Milima ya Himalaya na mipaka mingine ya mabamba ya ardhi yalionwa kuwa salama kwa kiasi fulani kutokana na matetemeko ya ardhi. Hata hivyo, katika siku za karibuni, hata maeneo hayo yamepatwa na matetemeko ya ardhi yenye kuangamiza, ingawa yalikuwa ya ukubwa mdogo kuliko matetemeko ya Himalaya. Tetemeko la ardhi la 1967 lilisababisha marekebisho ya ramani ya eneo la tetemeko la ardhi, na kusababisha kuondolewa kwa eneo lisilo la tetemeko la ardhi kutoka ramani. Eneo la Koyna limetambuliwa kuwa eneo la tetemeko la ardhi la nne, na hivyo kuwa hatari kubwa. Kutokea kwa tetemeko la ardhi la Killari mnamo 1993 kulisababisha marekebisho zaidi ya ramani ya kigaidi ambapo eneo la hatari ya chini au eneo la kigaidi la I liliunganishwa na eneo la kigaidi la II, na sehemu zingine za Deccan na India ya Peninsula zilileta chini ya eneo la kigaidi la III linalojumuisha maeneo yaliyochaguliwa kama maeneo ya hatari ya wastani. Utafiti wa hivi karibuni unaonyesha kwamba kadiri ufahamu wa hatari ya tetemeko la ardhi katika mikoa hii unavyoongezeka, maeneo zaidi yaliyowekwa kama hatari ya chini yanaweza kupewa kiwango cha juu cha hatari ya tetemeko la ardhi, au kinyume chake. Sehemu ya kaskazini mashariki ya nchi inaendelea kupata matetemeko ya ardhi ya wastani hadi makubwa kwa vipindi vya mara kwa mara ikiwa ni pamoja na matetemeko mawili makubwa yaliyotajwa hapo juu. Tangu mwaka wa 1950, eneo hilo limepata matetemeko kadhaa ya ardhi. Kwa wastani, eneo hilo hupata tetemeko la ardhi lenye nguvu zaidi ya 6.0 kila mwaka. Visiwa vya Andaman na Nicobar pia viko kwenye mpaka wa kati ya mabamba na mara nyingi hupata matetemeko ya ardhi yenye kuharibu. Ongezeko la hatari ya matetemeko ya ardhi ni kwa sababu ya kuongezeka kwa shughuli za maendeleo zinazosukumwa na mijini, maendeleo ya kiuchumi na utandawazi wa uchumi wa India. Kuongezeka kwa matumizi ya vifaa vya teknolojia ya juu na zana katika viwanda vya utengenezaji na huduma pia imewafanya kuwa na uwezekano wa kuharibiwa kutokana na kutetemeka kwa ardhi kwa kiasi kidogo. Matokeo ni kwamba, kupoteza uhai wa kibinadamu si jambo pekee linaloamua hatari ya matetemeko ya ardhi tena. Uharibifu mkubwa wa kiuchumi unaosababisha kuanguka kwa uchumi wa eneo au mkoa baada ya tetemeko la ardhi unaweza kuwa na matokeo mabaya ya muda mrefu kwa nchi nzima. Athari hiyo ingeongezeka zaidi ikiwa tetemeko la ardhi lingegonga jiji kubwa kama vile Delhi au Mumbai. Nini cha Kufanya Baada ya Tetemeko la Ardhi - Weka utulivu, washa redio au televisheni na utii maagizo yoyote unayosikia. - Jitenge na fuo na kingo za chini za mito. Mawimbi makubwa yaweza kuvuma. - Jitayarishe kwa matetemeko ya baadaye. - Kuzima maji, gesi na umeme. - Usiweke sigara na usitie match au utumie kiwasha sigareti. Usiwashe vifungo. Huenda kukawa na uvujaji wa gesi au mzunguko mfupi. Tumia tochi. - Ikiwa kuna moto, jaribu kuuzima. Ikiwa huwezi, piga simu kwa idara ya moto. - Ikiwa watu wamejeruhiwa vibaya, msiwahamishe isipokuwa wakiwa katika hatari. - Mara moja kusafisha bidhaa yoyote flammable ambayo inaweza kuwa imemwagika (alkohol, rangi, nk). - Kama unajua kwamba watu wamezikwa, waambie timu za uokoaji. Usifanye haraka na usizidishe hali ya watu waliojeruhiwa au hali yako mwenyewe. - Epuka mahali ambapo kuna nyaya za umeme zilizofungwa na usiguse kitu chochote cha chuma kinachogusa waya hizo. - Usinywe maji kutoka vyombo wazi bila kuwa kuchunguzwa na kuchujwa kupitia sieve, kichujio au kitambaa safi ya kawaida. Ikiwa nyumba yako imeharibiwa sana, utahitaji kuihamisha. Kukusanya vyombo vya maji, chakula, na dawa za kawaida na maalum (kwa watu wenye matatizo ya moyo, kisukari, nk.) - Usirudi kwenye majengo yaliyoharibiwa sana na usikaribie majengo yaliyoharibiwa. - Battery kuendeshwa tochi - Batteri ziada - Battery kuendeshwa redio - First Aid kit na mwongozo - Chakula dharura (vitu kavu) na maji (packed na kufungwa) - Mishumaa na mechi katika chombo waterproof - Chlorine vidonge au poda ya maji purifiers - Can opener. - Dawa muhimu - Fedha, Kadi ya Aadhaar na Kadi ya Ration - Kamba nene na kamba - Viatu vyenye nguvu