More than a thousand people have taken part in a protest march against fracking in Lancashire after minor earthquakes happened at the Preston New Road site on Friday.

Cuadrilla say they were not fracking at the time the tremors were felt, while the British Geological Survey (BGS) said the small earthquakes were "not unexpected since hydraulic fracking is generally accompanied by microseismicity (very small earthquakes that are too small to be felt)".

Fracking is the process that involves drilling into the ground, then pumping in water and chemicals to release gas.

One protester said he found the minor earthquakes "terrifying", adding: "I would say I'm shocked, but I'm not shocked. Fracking causes earthquakes."

Several minor tremors have been recorded since fracking began again at the Preston New Road site. Credit: ITV News

The magnitude recorded by the BGS on Friday was reportedly 0.3, while tremors felt on Thursday came in at -0.3 and -0.8.

Anything measuring zero or below is classified as "green", while recordings up to 0.5 are "amber", meaning fracking should proceed with caution.

Readings above 0.5 mean fracking should be suspended immediately.

Cuadrilla, the energy company which has begun fracking at the site, said they share their data with the BGS and the tremors were not strong enough to have been felt at surface level.

How shale gas is extracted. Credit: PA Graphics

BGS explained that they had "developed additional surface seismic sensors across the north of England" to help determine natural tremors and those induced by fracking.

"This dense network of sensors allows us to detect smaller earthquakes than we are typically able to do in other parts of the UK."

There are concerns fracking may cause earthquakes, and the chemicals could contaminate local ground water – affecting what comes out of people’s taps.

Opponents also fear an increase in noise and traffic pollution, and the pursuit for a new source of gas - a fossil fuel - is not compatible with efforts to tackle climate change.

One of those protesting was former Lib Dem leader Tim Farron who criticised the Government for allowing fracking - the extraction of shale gas from dep underground - "at the time we're meant to be heading towards a zero-carbon economy, but there's no sign of that whatsoever, when they are reducing investment in tidal and solar power."

A worker at the Cuadrilla fracking site in Preston New Road, Little Plumpton, Lancashire. Credit: PA

However, those in support of fracking claim it will reduce the UK's carbon-footprint.

A spokesperson for Lancashire for Shale: "By blocking the development of shale gas in Lancashire and elsewhere, campaigners risk locking us in to increasing dependence on higher emission imports whilst denying local people the opportunities, jobs and investment that a successful shale gas industry will be responsible for."

Saturday's protest came just days after three fracking protesters were release from prison after a six-week-stint behind bars for causing public nuisance by climbing on lorries in a bid to stop the fracking process at Preston New Road.

Simon Blevins, Richard Roberts and Rich Loizou were freed on Wednesday by Court of Appeal judges, who said their original sentences were "manifestly excessive".

Anti-fracking protesters have vowed to continue until fracking is banned, and as small earthquakes continue to be detected, it does not appear that they will stop anytime soon.