Thursday is the 50th anniversary of the Great Alaskan Quake, which measured magnitude 9.2 making it the second strongest earthquake in history. The Subcommittee on Energy and Mineral Resources in the US House of Representatives will mark the occasion with a hearing titled "Advances in Earthquake Science: 50th Anniversary of the Great Alaskan Quake". Which served to inspire a blog post, on Wednesday, on the NRDC's Switchboard blog, discussing the big need to study induced earthquakes, especially those related to hydraulic fracturing activities.
As we reported the other day, the state of understanding is that induced earthquakes connected to fracking operations are thought to be triggered by injection wells. When a site is hydraulically fractured, a mixture of sand, water, and fracturing chemicals, are pumped underground under high pressure, and are used to fracture rock (shale) that contains oil or gas deposits. After the well is injected, some highly toxic water is "produced" from the well, and the typical practice is to inject that water underground, in an injection well. It's thought that when the injected water reaches a geologic fault, it can lubricate the rock enabling an earthquake to occur prematurely.
The NRDC says "more research is urgently needed is induced seismicity" which are earthquakes "caused by human activities, including mining, water reservoirs, and energy production," unlike natural earthquakes which occur from movements of the Earth's crust.
It's known that some oil and gas drilling activities have induced earthquakes, and the NRDC blog post cites earthquakes linked to underground disposal of brine, or CO2 (carbon dioxide). The latter NRDC post talked about induced earthquakes at one field, but another nearby field with similar history including years of water injection did not exhibit induced earthquakes. It says that one cannot flatly say fracking or injection will cause earthquakes, but that earthquakes do get induced in some circumstances.
The urgency to study the issue comes from recognition, by the USGS, that a flurry of earthquakes recently in Oklahoma, including a magnitude 5.7 quake, were induced by wastewater injection and fracking operations.
USGS researchers have found an accelerated rate of earthquakes, above magnitude 3.0, in the central and eastern United States. The rate increased from 21 earthquakes per year in the period of 1967 to 2000, and during the period of 2010-2012 there were 300 earthquakes, 188 of those occurring in 2011.
Being areas where earthquakes are infrequent, these areas are not as well prepared with building codes and earthquake awareness as is, say, the West Coast, which of course sees lots of earthquakes each year. On the West Coast, as we reported the other day, Clean Water Action is raising an alarm over plans to expand hydraulic fracturing operations in the Monterey Shale. In addition to the significantly large shale deposits, the areas many fault zones include the famous San Andreas Fault which is already at a high risk of a major earthquake in Southern California.
The NRDC says "there are still big gaps in our scientific knowledge" regarding induced earthquakes. They call for expanded research by academic institutions and government agencies (like the USGS) into induced earthquakes. More knowledge could "help scientists develop strategies that could significantly reduce the chance that such earthquakes will occur." Finally, if there are places where the risks of induced earthquakes are too high, and cannot be mitigated, then risky activities must be prohibited. Why? "Energy production must not come at the expense of public health and safety"