By Dr. Arun Bapat
Anniversaries of natural happenings have been observed (or celebrated?) in various States since long. The NE Region had experienced a very large magnitude earthquake (of Magnitude = 8.7) on 12 June 1897. Today is the 120th Anniversary of this seismic event. Report on this earthquake by R D Oldham of Geological Survey of India (GSI) has initiated and established seismology on firm mathematical basis.
After the Bhuj earthquake of 26 January 2001 a number of organizations were established. At Government of India level the National Disaster Management Authority (NDMA) and National Institute of Disaster Management (NIDM) were established in 2005. At state levels, all States have established State Disaster Management Authorities (SDMAs). The aim of this exercise was to reduce the loss during disaster.
But even during a relatively less magnitude earthquake of 6.8 in Sikkim on 18 September 2011 it was not possible to save a single life. We have to think seriously why and where we went wrong? Whether it is planning, funding, organizational weakness, lethargic attitude, red tape or else? The answer to all these questions is change the focus of operational disaster management from post-disaster period to the pre-disaster period. Most of the disaster Management (DM) plans are focused and concentrated on post-seismic period. When the seismic shaking stops, the Disaster Managers rush to the site with stretchers, medical aid, food, mobile medical van and if required by helicopter etc and try to rescue the trapped people under the debris. They are able to save some trapped lives. But majority of the people are already dead. Unfortunately this is the present DM scenario in India. If the DM scenario is re-oriented from post-seismic to pre-seismic (including co-seismic period) it would be really effective in saving some lives. The pre-seismic efforts would include creating seismic awareness, educating people about various seismic precursors etc
The disastrous effects of earthquake could be reduced considerably if new houses are constructed and old houses are strengthened as per the seismic codal provisions of the relevant codes from Bureau of Standards. But this is a time and money consuming process.
If following points are followed it would be extremely useful to mitigate seismic disaster. These precursory observations are mainly valid for earthquake of magnitude 5.5 or more. For earthquakes of magnitude 5.0 or less this may not be observed. We would discuss three types of precursors (a) electronic type and (b) Using satellite data on real time basis and (c) biological precursors (human and animal behavior).
Electronic type seismic precursors
Before the occurrence of any moderate to large magnitude earthquake the hypocentral area (the underground location where actual rupture process occurs) gets heated. As the temperature rises, the geomagnetic field of the earth at that location goes on decreasing. The decrease adversely affects the propagation and reception of electromagnetic waves and communication. About two days before earthquake the landline telephone communication gets disturbed. The talk is accompanied with disturbing noise (khar-khar).
About 30 to 40 hours before earthquake, the reception on radio in the potential epicentral area, gets disturbed. If one is listening to a Radio programme at 1000 kHz, then the same station could be heard at 1100, 1200..1400 kHz etc.
There is an excellent example of difficulty in electromagnetic communication. Such communication system is used by police, fire brigade, army, aero planes etc for quick and easy communication. When an aero plane is approaching an airport, it contacts the airport by sending an electromagnetic communication system to the Airport Control Tower (ACT). The plane gets permission for landing. Few hours before the occurrence of magnitude 8.0 Haiti earthquake of Jan 2010, an aero plane could not establish contact with the airport and was forced to be diverted to other airport.
About ten hours before earthquake, the television reception gets disturbed. The disturbances are audio, visual and spectral. The number of disturbances goes on increasing till the occurrence of earthquake. This was observed very effectively before the Latur (1993) earthquake.
The next and most important observation is from Mobile telephone. About 100 minutes before occurrence of moderate to large magnitude earthquake mobile phones are affected. If one or two mobile telephones are not functioning it may be due to defect of instrument. In case all mobile telephones within a large area of 15 or 20 km or more area are affected then it may be examined by calling places at longer distances (20 to 50 km or more). If so then it could be assumed that earthquake could occur. If all mobile telephones are not functioning then it could be sign of earthquake within next 100 minutes.
It would thus be seen that the electronically connected seismic precursors give indications initially about 40 hours before, then of about 10 hours then it reaches a level of 100 minutes.
Using satellite data on real time basis
Satellite borne data could be effectively used for earthquake forecasting and prediction on 24 x 7 bases. Some parameters could be extremely useful for short term earthquake prediction. These are Out Going Long Wave Radiation (OLR) and Total Electron Content (TEC). These are freely available on India Meteorological Department web and number of other webs pages. These data have been used fruitfully in the case of Bam (Iran), Bhuj (India), Muzaffarabd (Pakistan), Sumatra (Indonesia) Sichuan (China) and Tohoku (Japan) Earthquakes. The North Eastern Satellite Application Center (NESAC) near Shillong has been doing good work and it could be requested to scout for such observations.
Biological seismic precursors
It has been reported and confirmed that all zoological specimen behave in abnormal behavior about ten hours before earthquake. All animals shout and become violent. If the animals are tied by rope or chain they want to be free. Domestic animals such as cows, buffaloes, dogs, cats, horses, lambs etc show abnormal behavior about ten hours before earthquake. Birds do not sit on trees or in nest. They fly in groups at low height with shrilling noise. Rodents and reptiles come out of their hidings and move in a directionless way and they are frightened. Insects like millipedes, centipedes, ants, move in haphazard manner.
Domestic pets also shout and may become silent or violent.
About 15 to 30 hours before the occurrence of medium to large earthquake the number of Patients from OPD and delivery cases shows a sudden rise. The rise could be three to five times the daily average value. With high magnitude it could be of the order of about five to seven times the daily values.
Some ailments such as High Blood Pressure, Headache, Vomiting, Migraine, Uneasiness, and Depression are caused by some disturbance or provocation. But these ailments are highly manifested without any cause or provocation. Patients are more confused due to this sudden intensification of ailment.
Clubbing the three precursors would give a realistic visualization of the seismic situation which could be effectively used to mitigate the seismic disaster.
A rough estimate of earthquake magnitude and effective distance is possible in a thumb rule type derivation. For magnitude 6.0 to 7.0 the precursors are highly predominant up to a distance of about 250 to 350 km radius. For magnitude large than 7.0 it could be observable up to 500 to 600 km radius. This is rough estimate and there could be variation of some percentage. These instructions may be circulated to all the concerned departments. In the seismically active regions
, these may be broadcast on radio and telecast on television.
If these instructions are followed it would be possible to reduce the loss of lives and property during earthquake.
The author is a Research Seismologist from Pune [email protected]