We already know that large dams cause small local tremors. This is a much larger event. To put it in context, it is larger than the Newcastle earthquake, which killed people. Clearly, more work needs to be done to understand anthropogenically induced earthquakes. This has implications for the proposed burying of CO2 emitted by fossil fuel electricity generation systems.
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Potentially induced earthquakes in Oklahoma, USA: Links between wastewater injection and the 2011 Mw 5.7 earthquake sequence

Katie M. Keranen, Heather M. Savage, Geoffrey A. Abers and Elizabeth S. Cochran

Geology, June 2013, v. 41, p. 699-702, first published on March 26, 2013, doi:10.1130/G34045.1

Abstract

Significant earthquakes are increasingly occurring within the continental interior of the United States, including five of moment magnitude (Mw) ≥ 5.0 in 2011 alone. Concurrently, the volume of fluid injected into the subsurface related to the production of unconventional resources continues to rise.

Here we identify the largest earthquake potentially related to injection, an Mw 5.7 earthquake in November 2011 in Oklahoma. The earthquake was felt in at least 17 states and caused damage in the epicentral region. It occurred in a sequence, with 2 earthquakes of Mw 5.0 and a prolific sequence of aftershocks.

We use the aftershocks to illuminate the faults that ruptured in the sequence, and show that the tip of the initial rupture plane is within ∼200 m of active injection wells and within ∼1 km of the surface; 30% of early aftershocks occur within the sedimentary section. Subsurface data indicate that fluid was injected into effectively sealed compartments, and we interpret that a net fluid volume increase after 18 yr of injection lowered effective stress on reservoir-bounding faults.

Significantly, this case indicates that decades-long lags between the commencement of fluid injection and the onset of induced earthquakes are possible, and modifies our common criteria for fluid-induced events. The progressive rupture of three fault planes in this sequence suggests that stress changes from the initial rupture triggered the successive earthquakes, including one larger than the first.

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Have you got a link to that info MV?

Podzol: I (just then) googled the doi: ####. (referenced above) and got the abstract – which I had read in and copied from Geology (and then added paragraph spaces). The full article is behind a paywall. However – the search revealed the full article. See below.

:)

http://geology.gsapubs.org/content/early/2013/03/26/G34045.1.abstract

http://www.csun.edu/~dorsogna/nodrill/Geology-2013-Keranen-G34045.1.pdf

Thanks for doing my googling!

What is your take on it? It is hurting head to imagine such huge earthquakes from injection, the pumping pressures, the time delays… I need a 3-D animation.

podzol said:

Thanks for doing my googling!

What is your take on it? It is hurting head to imagine such huge earthquakes from injection, the pumping pressures, the time delays… I need a 3-D animation.

.

The rocks were strained and had already faulted. It is quite likely that water leaked from the re-hydrated formations into the fault zones and lubricated them to failure.

However, water leaking from rocks into fault zones is a normal fault-lubrication mecchanism.

There is a strong possibility that this was going to occur anyway, without man’s interference. Without haveing a microseismic array set up long before the basin was mined for oil and re-injection started, it is impossible to figure out whether we delayed the inevitable, increased the likelihood and magnitude, or had no impact.

http://www.abc.net.au/science/articles/2012/10/22/3613607.htm

This is an article about removing water from the ground and a M5.1 earthquake. The opposite of the OP article. I am less inclined to accept this notion.

However it could be possible if originally, aseismic creep on the fault was lubricated by smectite clays kept fully hydrated below the water table. If the water table were lowered and the smectites dehydrated, stick-slip movement on the fault would most likely become the dominant movement mechanism. Earthquakes occur when movement is stick-slip.

Given that the major movement on the fault was 3km below ground, I feel (without specific evidence) that it is unlikely to have been exhumed from below the water table. 3km water wells are unusual.

Michael V said:

However it could be possible if originally, aseismic creep on the fault was lubricated by smectite clays kept fully hydrated below the water table.

I’m going to start telling people they have a head full of smectite clay

This adds some more science to this topic, to help us understand it a bit better.

Two-phase fluid flow properties of cataclastic fault rocks: Implications for CO2 storage in saline aquifers
Christian Tueckmantel, Quentin J. Fisher, Tom Manzocchi, Sergey Skachkov and Carlos A. Grattoni

Geology, January 2012, v. 40, p. 39-42, doi:10.1130/G32508.1

Abstract
Fault rocks can function as barriers to subsurface fluid flow and affect the storage of CO2 in geological structures. Even though flow across faults often involves more than one fluid phase, it is typically modeled using only single-phase functions due to a lack of fault rock relative permeability data and complexities in incorporating two-phase flow properties into flow simulations.

Here we present two-phase fluid flow data for cataclastic fault rocks in porous sandstone from the 90-Fathom fault (northeast England). The study area represents a field analogue for North Sea saline aquifers of Permian–Triassic age that are currently being considered for CO2 storage. We use the experimental data to populate a synthetic model of a faulted saline aquifer to assess the impact of these fault rocks on CO2 injection.

We show that even fault rocks with low clay contents and very limited quartz cementation can act as major baffles to the flow of a non-wetting phase if realistic two-phase properties are taken into account. Consequently, pressure may increase far more rapidly in the storage compartment during CO2 injection than anticipated based on models that only incorporate absolute fault rock permeabilities.

To avoid high pressures, which may lead to hydrofracturing and CO2 leakage, either more complex injection strategies need to be adopted or seismic data acquired to ensure the absence of faults in aquifers selected for CO2 storage.