Reading seismic signals
Though seismic activity is rarely preventable, its onset will be preceded by several mundane signals that can be read and recognised by an ordinary citizen
During the recent past, there have been a number of publications, discussions and meetings about the possibility of a large magnitude earthquake in the Himalayas that have left most people with a deep sense of apprehension.
To deal with disasters, we have, at the national level, the National Disaster Management Authority (NDMA) and at the state level, there are State Disaster Management Authorities (SDMAs). In addition, there is a mighty rescue organisation, the National Disaster Relief Force (NDRF), with similar agencies at the state-level known as SDRFs.
These agencies are doing commendable work, but all their rescue efforts are mostly concentrated and oriented towards the post-disaster period. There is almost no (or minimal) activity for the pre-disaster period. Here, I propose to discuss some reliable seismic precursors that could be observed and recorded by a common man a few hours before a seismic contingency.
These precursors are of different types – electric, electronic, magnetic, medical and veterinary. No special training is required to observe these precursors. For effective implementation of this, a committee may be formed across various administrative levels such as the gram panchayat, zila parishad, each ward of municipal areas, et al. Similarly, social groups of interested persons may also be formed. If possible, include at least one doctor and one engineer in the group.
Hydel precursors: About three to four weeks before a very large earthquake of magnitude 8 or more, dry wells, drains, rivulets, brooks and the like are flooded with water oozing from the ground. Sometimes, the force is so great that the water comes out in the form of a fountain. This was found prior to the Bhuj earthquake of January 26, 2001. Similar incidents have occurred prior to the 1905 Kangra earthquake and the 1935 Quetta earthquake.
Thermal precursors: It has been observed that the local maximum and minimum temperatures in the potential epicentral areas show a rapid and remarkable rise. The India Meteorological Department (IMD) site would give the necessary information. The rise in temperature is quick and is manifested within about three to five days. It could be three to five degrees Celsius and, on the earthquake day or sometime before, it could be as high as plus-7 to plus-12 degrees Celsius. This has been observed before all large magnitude earthquakes in the world. The epicentre of the Great Sumatra earthquake and tsunami of December 26, 2004, was in the sea. It was observed through satellites that the sea surface temperature (SST) above the epicentral area was higher by about five to seven degrees C.
Communication Precursors: About three to four days before an earthquake, radio programmes are disturbed. If a radio station is broadcasting at 1,000 kHz, this would be heard in the potential epicentral area at higher frequencies such as 1,100, 1,200 and 1,500 kHz. Similarly, conversations on landline telephones are highly disturbed. A clear background noise (chatter) can be observed during calls.
Prior to the Uttarakhand earthquake of 1991, the entire police wireless network had become non-functional. No wireless signal was reaching Uttarakhand. There is an interesting example from a Caribbean island country that had suffered a magnitude 8 earthquake and the death toll was about 100,000. A few hours before the earthquake, a commercial plane was trying to contact the Air Traffic Control seeking permission to land. The pilot could not establish contact and was forced to divert to another airport.
Medical Precursors: About two to three days before an earthquake, hospitals would observe a sudden and sharp rise in the number of delivery cases and also abortions. This was observed for the first time prior to the Spitak earthquake in Armenia (then USSR) in 1988. I have collected data from three hospitals at Latur, Bhuj and Port Blair. If the number of deliveries on an average is three to four then it starts rising by a factor of three to five. On the day of the earthquake, it was seen to be about seven times the average rate.
This happens about 30 to 50 hours before the earthquake. Similarly, the number of outpatients shows a rise by a factor of seven to nine. Their ailments are mostly a sudden rise in blood pressure, uneasiness, a sense of fear and jitters, itching, vomiting and a sense of confusion. This is seen about 24 hours before an earthquake.
Veterinary Precursors: The entire zoological specimen of animals, birds, reptiles, and insects is seen confused and moving in a directionless manner. Even domestic pets become violent and attack their owner. Birds fly at a low height in small groups and with a high amount of shrilling. This highly reliable and assured precursor is seen about 15 hours before an earthquake.
Telecasting Precursors: The audio, visual and spectral receptions on television sets in the area are also disturbed. The number of disturbances keeps increasing till an earthquake occurs. This is a sure precursor and occurs about 15 hours before an earthquake.
Mobile Telephone Precursors: About 100 minutes before an earthquake, all mobile telephones in the potential
epicentral area become non-functional. Non-functioning of one or two mobile telephones should not be taken as
any seismic indicator. If users of landline telephones in locations within a 30-50 km radius have similar observations, close all electric, water and gas connections in the house and come out and
sit or stand away from the collapse
range of structures and mobile telephone towers.
(The author is a research seismologist and former chief of earthquake research at the Central Water and Power Research Station. The views expressed are strictly personal)
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