What happens when you ASS U ME?

Keranen et al., 2013

After reading a recent study paper that links large (≥ Mw 5.0) earthquakes in Oklahoma to wastewater disposal, I am left with the dissatisfied feeling that the title and media buzz surrounding the paper’s release is a bit over-sensationalized.

The paper is a solid piece of seismology that locates three major events with hundreds of aftershocks — if only the story ended there (then it probably wouldn’t have gotten into Geology). Where it falters scientifically is the supposition that these events are “linked” to wastewater injection wells. The only link, that is clear, is that theses earthquakes occurred near the injection wells. The authors cite well-documented studies that have data, which correlate seismicity with fluid injection. This paper on the other hand, did not have any such data. What it does have is a lot of suppositions and cartoon diagrams of what could be happening.

The physics of induced seismicity is well established, from laboratory beer can experiments, to field studies in Rangely, CO and Dallas-Forth Worth, TX. We know how earthquakes are triggered. What we don’t know is if the Oklahoma earthquakes are indeed triggered events — in my humble seismologic opinion, this question is still unanswered. The authors did not sufficiently present data to validate this claim:

Here we present a potential case of fluid injection into isolated pockets resulting in seismicity delayed by nearly 20 yr from the initiation of injection, and by 5 yr following the most substantial increase in wellhead pressure. — Keranen et al., 2013 (Geology)

There are other ways to induce seismicity in the midcontinent. Let us discount those other ways first, then we can make educated hypotheses as to what else could be causing these intraplate earthquakes. When we, as scientists, seek to prove our assumptions without considering other explanations, the end result is damning to the community as a whole.

Disclosures:
(1) As a seismologist, I would be scientifically thrilled to induced and study large (≥ Mw 8.0) in the field. Unfortunately, I do not see (in the data) that these moderate earthquakes in Oklahoma are indeed induced.
(2) I am neither for nor against oil companies and their drilling practices. It is what it is.
(3) I am against inconclusive studies that mislead other scientists and the general public with sensationalism and unfounded assumptions. That’s just wrong.
(4) I have tremendous respect for the authors of this paper as scientists, I just think the conclusion is a bit unpolished. The study requires a more thorough treatment in a longer publication.
(5) Everything here is my own opinion.

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~ by Jefferson C. Chang on 27 March 2013.

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