Are earthquakes more common in mining regions than they would otherwise be? e.g. is the frequency of earthquakes in those regions different when mining is occurring than when it is not?
I am interested in earthquakes generally, but also particularly interested in earthquakes strong enough to have damaging impacts (to life and infrastructure).
Yep, mining can trigger earthquakes.
According to a Scientific American article:
We've been monitoring [The Geysers] since 1975. All the earthquakes we see there are [human] induced. When they move production into a new area, earthquakes start there, and when they stop production, the earthquakes stop.
This is talking about geothermal power. They create small little fractures, which cause tiny earthquakes. They then harness this power for electricity.
Earthquakes can also be caused by coal mining and other mining, according to this study:
Klose has identified more than 200 human-caused temblors, mostly in the past 60 years. "They were rare before World War II," he said.
Most were caused by mining, he said, but nearly a third came from reservoir construction.
Oil and gas production can also trigger earthquakes, he added.
Three of the biggest human-caused earthquakes of all time, he pointed out, occurred in Uzbekistan's Gazli natural gas field between 1976 and 1984 (map of Uzbekistan).
Another study also concluded this.
The Short Answer is Yes. The consensus is that humans can prematurely trigger earthquakes, and this paper in 1986's EPSL annual reviews seems to be in full support. There is also this paper which suggests that mining induced earthquakes are quite common. A third paper published in Science last year also suggests that hydraulic fracking can cause earthquakes. There are many more papers on this subject, easily found using google scholar, as it is contentious to both the public and scientists alike.
The East Midlands region of the UK is currently experiencing small earthquakes that are believed to be related to mining activities. The British Geological Survey has a page about these events: New Ollerton Earthquake Activity.
In addition to triggering natural earthquakes, (as pointed out by @hichris123) Mines can also be sources of artificial seismic activities due to mine collapses and/or explosives.
Miners will generally try their best to keep their mine shaft stable, but their methods aren't 100% accurate. Sometimes mining in an unstable area or with the lack of support to a mine will cause the shaft to collapse, killing anyone still in it. When this happens, there can be a chance that an earthquake could be felt from a nearby town or city.
Are earthquakes more common in mining regions than they would otherwise be?
While there can be earthquakes in mining regions due to other reasons, yes, they are. When a mine collapses, the releasing of the rocks can be so abrupt that kinetic energy is discharged in the form of a low-magnitude earthquake. This is also known as a form of induced seismicity, and earthquakes resulting from induced seismicity generally aren't that serious.
When you google 'earthquakes due to mining', the following blurb will appear:
The six miners and three rescuers that were killed in the magnitude-3.9 earthquake due to the collapse of the Crandall Coal mine are now memorialized at the site. ... The abrupt release of elastic strain in the rocks during a mine collapse discharges energy in the form of seismic waves.
So this is a good example of induced seismicity.
e.g. is the frequency of earthquakes in those regions different when mining is occurring than when it is not?
Since you mentioned mining regions, it will be assumed that a collapsing mine would be more of a common occurrence in a mining region than anywhere else. So yes, the difference would be that there are more seismic waves creating earthquakes in a mining region compared to you're average city, because less mining is occurring in a city that in a mountain. But when no mining is in progress an a mining region, there will be less human-induced earthquakes.
