Being vigilant will help:
Earth tremors - no cause for alarm, says GSMB
As a country considered free from earthquakes in its recorded
history, Sri Lankans hardly bothered about facing disasters caused by
earthquakes. But the 2004 December 26 Tsunami which brought us
disastrous effects of a huge earthquake near Indonesia, compelled us to
be ever vigilant on earthquakes happening around the globe.
Dr. N.P. Wijayananda
The constant vigilance of Sri Lankans for Tsunami warnings has made
them more sensitive towards any tremor after the tragedy the country
faced on Boxing Day in 2004. Therefore, the earth tremors reported in
the Ampara district since November 2012, has made the people more
vigilant about the situation.
Though there are no major damages to properties due to these low
level tremors people are more concerned about the situation as they have
felt nearly five such tremors within a day since November 2012. The
Geological Survey and Mines Bureau (GSMB) is also concerned about the
situation as they receive seismic data from the seismic station in
Pallekele about these tremors.
Commenting on the situation, Chairman of the GSMB, Dr. N.P.
Wijayananda said that the GSMB is continuing its efforts to trace the
real cause behind these tremors after deploying their teams in the
According to Dr. Wijayananda during the year 2012, 21 earth tremors
have been recorded in different parts of the country in the seismic
stations. They have been reported in Kothmale, Maduru Oya national Park,
Allanmulla in Moneragala and near Veheragala reservoir. Nearly 15
tremors have been recorded in Ampara area since November 24.
The Seismic Data and Tsunami Alert Centre (SDTAC) of the GSMB is
receiving all these data through the seismic station at Pallekele, Kandy
and 10 other global stations.
"We had reported more tremors during 2012. It doesn't mean that these
tremors are more frequent. The reason for the number of incidents
reported to be high is that people are more aware about these incidents.
Almost all the people have mobile phones and they report to us or they
report to the media when there is such an event. There is a better flow
of information", he said.
"We have very advanced and sophisticated equipment at our seismic
stations and it picks up even the very low level tremors. Some tremors
recorded here are even without the knowledge of the people there", he
"People are saying a lot of things about earth tremors but we go only
by our recordings. It is difficult to rely solely on the reports from
the people. If there is any earth tremor that is recorded at our
centre", Dr. Wijayananda said, pointing to a computer which constantly
indicate the earth tremors and earthquakes around the world.
"What I can say is that none of the tremors reported in the country
are damaging. They are only vibrations", he said.Explaining further, Dr.
Wijayananda said if such tremors have to be damaging it has to have the
effect to cause a glass on a table fall, or cause glass windows to
crack. But non of these tremors had such effects.
"Some people say that some walls of the houses were cracked due to
these tremors. This can happen because of the tremor as well as due to
the weakness of a structure or the foundation. If the tremor is powerful
to crack a wall it should first shatter the glass on windows.
At least the tiles on the roof had to fall. If someone is complaining
their walls are cracked that may not be due to the tremor but due to the
weakness of foundation. So far people have not reported of such thing",
According to Dr. Wijayananda there are two possibilities for these
tremors. One is natural reasons and the other, man made.
"We earlier had experience about man made tremors. One such incident
was reported in Colombo when an underwater blast was carried out to
deepen the Colombo harbour. That was known to us and people did not
panic when they were told about the reason for the tremor", he said.
The Ports Authority had informed the GSMB about these underwater
blasts and it had given them the required parameters to carry out the
underwater blasts. The operations at the Colombo harbour had gone on for
more than two months and something went wrong with the particular blast
causing tremors in Colombo, he said.
"A situation similar to Ampara was also reported in Kirinda area in
Hambantota district in 2011 also, and the GSMB observed the situation.
When we carried out the investigations we found that the blasting
program carried out in the harbour tallied with the tremors reported in
Hambantota area. We were not aware of the situation and one company had
undertaken to carry out those blasts from the Ports Authority. People
got panicked. But later we found that it was the reason for these
tremors", he added.
One unusual things reported by the people in Ampara is that they hear
a vibration along with the tremor.
" If it is a natural tremor there will be no unusual sound. According
to our observations most of these tremors were reported during week days
and day time.
Therefore there is a good possibility that these tremors are relating
to man made incidents", he said.
When the tremors were reported in Ampara, the first reaction of the
GSMB was to check with the construction work of the Oluvil harbour but
they said no such activity was taking place there.
"Again we double checked with the Government Agent and asked whether
there are any deep piling in Ampara. The answer to that also was not
positive. If there is such activity there may be tremors but there
cannot be a sound", he said.
The next reaction of the GSMB was to establish mobile seismic units
there. But with the rainy season the teams could not travel to the areas
where these tremors were reported. Therefore they had to withdraw from
the area in the first week of December.
"What we tried through these mobile units was to check whether they
can detect the tremors that cannot be detected by the Pallekele station.
But the tremors detected by these mobile units were also recorded at the
Pallekele station", he said.
The other doubt the GSMB had was whether these tremors were caused by
blasts at the metal quarries, since there were a huge demand for
construction material."Therefore we carried out an artificial blast at a
metal quarry. But it also did not create such a tremor", he said."When
the water levels of the reservoirs increased also there is a possibility
of experiencing such tremors. This may happen in Victoria reservoir as
the water column is very high. In Ampara we have the Senanayaka Samudra.
There is no such water column in Senanayaka Samudra as in Victoria,
and there was no such water level in Senanayaka Samudra in November to
cause such tremor.
However, these tremors have been reported around Senanayaka Samudra
and the exact locations of the tremors are scattered around the jungle
terrain around Senanayaka Samudra.
"During the rainy season our teams could not reach these places to
carry out investigations.
Therefore with the two tremors reported in the area on January 25, we
have decided to carry out a long term investigation by deploying two
teams in the area. They are ready to start their investigations on
Wednesday", he said.
The Government Agent in Ampara and the Sri Lanka Army will also
extend their assistance to carry out these investigations. "What we
request the public or any other company is that if they are engaged in
activities in these areas that may cause such tremors please let us know
about it and if the activity is legal we can help them. The bureau has
the capacity to do that. Then people will not panic. People believe us
if they are informed of the real situation", Dr. Wijayananda said.