From: USGS
Seismicity of the coterminous United States and surrounding regions, 2009–2012. Black dots denote earthquakes with a magnitude ≥ 3.0 are shown; larger dots denote events with a magnitude ≥ 4.0. Background colors indicate earthquake hazard levels from the U.S. National Seismic Hazard Map (NSHM). Learn more about the NSHM at http://earthquake.usgs.gov/hazards/?source=sitenav. |
The number of earthquakes has increased dramatically over the past
few years within the central and eastern United States. Nearly 450
earthquakes magnitude 3.0 and larger occurred in the four years from
2010-2013, over 100 per year on average, compared with an average rate
of 20 earthquakes per year observed from 1970-2000.
This increase in earthquakes prompts two important questions: Are
they natural, or man-made? And what should be done in the future as we
address the causes and consequences of these events to reduce associated
risks? USGS scientists have been analyzing the changes in the rate of
earthquakes as well as the likely causes, and they have some answers.
USGS scientists have found that at some locations the increase in
seismicity coincides with the injection of wastewater in deep disposal
wells. Much of this wastewater is a byproduct of oil and gas production
and is routinely disposed of by injection into wells specifically
designed for this purpose.
Review Article on Injection-Induced Earthquakes
U.S. Geological Survey geophysicist William Ellsworth reviewed the issue of injection-induced earthquakes in a July 2013 study published in the journal Science.
The article focused on the injection of fluids into deep wells as a
common practice for disposal of wastewater, and discusses recent events
and key scientific challenges for assessing this hazard and moving
forward to reduce associated risks.
What is Induced Seismicity?
Although it may seem like science fiction, man-made earthquakes have
been a reality for decades. It has long been understood that earthquakes
can be induced by impoundment of water in reservoirs, surface and
underground mining, withdrawal of fluids and gas from the subsurface,
and injection of fluids into underground formations. MORE
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