London, Feb 26 : A new study has suggested that heavy downpours of rain could cause earthquakes in landscapes full of caves and channels by escalating pressure within underlying rock.
It is already known that rainfall can cause tremors. Places like Germany, Switzerland and France have experienced small earthquakes following heavy rainfall.
Some experts have suggested that although the rainfall in these areas was heavy, the fact that rain could lead to an earthquake at all signifies that it takes very little to produce a tremor.
However, Steve Miller, a geologist at the University of Bonn, Germany, disagrees, saying that the amount of water needed to trigger tremors is much more than previously thought, and that it is the landscape of a particular area that plays a key role in the incidence of rain-triggered earthquakes.
In the new study, Miller points out that all the three documented events of Germany, Switzerland and France occurred in a particular type of landscape known as karst.
Karst landscape features a distinctive topography of soft carbonate rock riddled with deep fissures, underground channels and cave systems.
These characteristic features are carved out when carbonate bedrock, typically limestone or dolomite, is dissolved slowly by the action of slightly acidic rainwater over thousands of years.
According to Miller, these structures are the key, reports New Scientist magazine.
He explained that on non-karst land surfaces, rainfall puts pressure on the Earth in a comparatively even fashion, and is usually quite swiftly carried away by surface rivers and streams. Consequently, the pressure of the rainfall on any underlying fault is small.
On the contrary, in karst, rain pours into the channels and caves, thus running deep into the rock. As a result the pressure of the rain rises inside the rock, which subsequently makes rain trigger earthquakes.
Miller said that increasing water pressure inside a rock is one of the three ways to break it, the other two being squeezing and stretching the rock.
The study is published in the Geophysical Journal International.