Induced seismicity
Induced seismicity is typically earthquakes and tremors that are caused by human activity that alters the stresses and strains on Earth's crust.
[1] The Human-Induced Earthquake Database (HiQuake) documents all reported cases of induced seismicity proposed on scientific grounds and is the most complete compilation of its kind.
The consequences of the induced seismicity could disrupt pre-existing faults in the Earth's crust as well as compromise the seal integrity of the storage locations.
For example, waste water from oil and gas production and carbon dioxide from a variety of industrial processes may be managed through underground injection.
[citation needed] The column of water in a large and deep artificial lake alters in-situ stress along an existing fault or fracture.
The 6.3 magnitude 1967 Koynanagar earthquake occurred in Maharashtra, India with its epicenter, fore- and aftershocks all located near or under the Koyna Dam reservoir.
After a landslide almost filled the reservoir in 1963, causing a massive flooding and around 2,000 deaths, it was drained and consequently seismic activity was almost non-existent.
On August 1, 1975, a magnitude 6.1 earthquake at Oroville, California, was attributed to seismicity from a large earth-fill dam and reservoir recently constructed and filled.
[31] Mining affects the stress state of the surrounding rock mass, often causing observable deformation and seismic activity.
[41] The 2011 Oklahoma earthquake near Prague, of magnitude 5.8,[42] occurred after 20 years of injecting waste water into porous deep formations at increasing pressures and saturation.
[5] Prior to April 2015 however, the Oklahoma Geological Survey's position was that the quake was most likely due to natural causes and was not triggered by waste injection.
More than 1,000 events with magnitudes (ML) between 0.7 and 4.3 (the largest earthquake ever associated with gas storage operations) and located close the injection platform were recorded in about 40 days.
[54] HDR and EGS systems are currently being developed and tested in Soultz-sous-Forêts (France), Desert Peak and the Geysers (U.S.), Landau (Germany), and Paralana and Cooper Basin (Australia).
In November 2017 a Mw 5.5 struck the city of Pohang (South Korea) injuring several people and causing extensive damage.
[61] For example, several cases of larger magnitude events (M > 4) have been recorded in Canada in the unconventional resources of Alberta and British Columbia.
Injection of fluids also increases the pore pressures in the reservoir, triggering slip on existing rock weakness planes.
Wastewater injection, hydraulic fracturing, and secondary recovery after oil extraction have all contributed significantly more to induced seismic events than carbon capture and storage in the last several years.
One such example is massively increased induced seismicity in Oklahoma, USA caused by injection of huge volumes of wastewater into the Arbuckle Group sedimentary rock.
[71] It has been shown that high-energy electromagnetic pulses can trigger the release of energy stored by tectonic movements by increasing the rate of local earthquakes, within 2–6 days after the emission by the EMP generators.
Earthquake hazards can include ground shaking, liquefaction, surface fault displacement, landslides, tsunamis, and uplift/subsidence for very large events (ML > 6.0).
Because induced seismic events, in general, are smaller than ML 5.0 with short durations, the primary concern is ground shaking.
Using the framework, the probability of exceeding a certain level of ground shaking at a site can be quantified, taking into account all the possible earthquakes (both natural and induced).
Formations of the rocks, subsurface structures, locations of faults, state of stresses and other parameters that contribute to possible seismic events are considered.
Vulnerability is defined as the potential of impact to those entities, for example, structural or non-structural damage to a building, and loss of well-being and life for people.
Nevertheless, when the seismic events are felt and cause damages or injuries, questions arise from the public whether it is appropriate to conduct oil and gas operations in those areas.
On October 6, 2015, people from industry, government, academia, and the public gathered together to discuss how effective it was to implement a traffic light system or protocol in Canada to help manage risks from induced seismicity.
[98] Risk assessment and tolerance for induced seismicity, however, is subjective and shaped by different factors like politics, economics, and understanding from the public.
Normally there are two types of TLS – the first one sets different thresholds, usually earthquake local magnitudes (ML) or ground motions from small to large.
Nuclear explosions may instead release the elastic strain energy that was stored in the rock, strengthening the initial blast shockwave.
[103] The report found that only a very small fraction of injection and extraction activities among the hundreds of thousands of energy development sites in the United States have induced seismicity at levels noticeable to the public.
