ATHENS, April 27 (Xinhua) -- Air pollution linked to car traffic declined by up to 50 percent, seismic noise related to human activity down by at least 30 percent compared with the pre-lockdown days, scientists at the Athens National Observatory have been impressed with Greeks' compliance with the full lockdown the government imposed on March 23 to curb the spread of COVID-19.
Nikos Michalopoulos, director of the observatory's Institute for Environmental Research and Sustainable Development, and Professor at the University of Crete, is participating in ongoing research conducted by the institute's experts regarding the effect of the people's movement restrictions on air quality.
"When we compared the period March 1-23, 2020, to previous years when they were no movement restrictions in place, we did not observe major significance," he told Xinhua in a recent interview.
"As of March 23 until today (April 24) we are recording a significant decrease in certain emissions that are linked to specific types of pollution, like car traffic. In this case, we have seen a decline reaching up to 50 percent (compared to the three-week period 1-23 March)," he said.
"Athens' air pollution regarding CO2 has shrunk by about 35-40 percent as of March 23 until today," he added.
However, the professor has foreseen that the data would rise again rapidly once the lockdown is lifted starting from May 4.
"I believe that after Monday, May 4, when the measures will be lifted, we will gradually see, even within a few days, the change. We want to see how much time it will take to humans to push the atmosphere back to pre-lockdown levels," he noted.
Michalopoulos and his team are in constant communication with other scientists across Europe with the aim to release a combined study, as similar outcomes from measurements have been reported from neighboring Italy to China, he said.
Christos Evangelidis, a researcher at the Institute of Geodynamics of the National Observatory of Athens, is responsible for the operation of the national broadband seismic network. He is taking part in another study on the relative silent seismic noise generated by human activity recorded across the globe this spring compared with the normal times.
In addition to earthquakes, seismometers are used also to record 24/7 the Earth's vibrations, including seismic noise linked to car traffic, industrial work and other human activities at higher frequency waves (above 1 Hertz), Evangelidis explained.
Looking at the measurements from the seismic station on the Acropolis hill or the parliament building and many others across the country, he has no doubt in the effectiveness of the lockdown.
"We observed that at higher frequencies the noises drop at least 30 percent after the lockdown measures. We keep seeing that. It is going down and remains down. This 30 percent reduction of the noise that we record in the seismic instruments is due to the anthropogenic activities, because the people are staying inside due to the lockdown measures and we record this silence, I would say," the expert said.
Evangelidis and his colleagues are also expecting a fast comeback to normal noise once the restrictions are eased. But until then, they are seizing the unique opportunity of this seismic silence to gather valuable data.
"Scientifically it would be interesting to see within cities where we have a small fault or a very small earthquake within the city that we couldn't see before because it was so much noise and now we might be able to observe it. We haven't seen anything yet, but we are looking closely," he told Xinhua, explaining that the silence has nothing to do with the earthquakes pattern.
"The earthquake activity remains the same. Earthquakes are happening all the time, especially in Greece we have a lot of earthquakes every day. We record them continuously. They are not affected at all," he said. Enditem
