January/February 2012

Expecting the Unexpected: Black Swans and Seismology


Probably no one in the seismological community, or any of the tens of millions of people who would subsequently be affected, was contemplating in detail the possibility of the strong mid-Atlantic region earthquake on the morning of 23 August 2011, during which strong ground motion was experienced by more people than in any other single event in U.S. history. It (inadvisably) emptied buildings in Manhattan and even (briefly) roused the U.S. government from its usual business of partisan siege warfare. Just a few hours before the Virginia earthquake, Colorado experienced one of the largest earthquakes in its history. As I write this, the media is abuzz with coverage of the largest earthquake in Oklahoma history. News from yet another tragic earthquake in Turkey is just now fading from the short-attention-span U.S. media.

2011 offered a number of examples of novel infrastructural and societal surprises atop the scientific ones … consider the ongoing “Earthquake Trial” in L’Aquila, Italy.

Even given the limited state of geological and seismological knowledge of the eastern United States and general intra-plate seismicity, the Virginia event was not especially surprising. Indeed things could have been much, much worse (e.g., consider the effects of a Charleston 1886-scale event of 6.5 or larger on the eastern seaboard), and the final result of this earthquake could be salutary if it leads to better appreciation of, and preparations for, eastern earthquakes. What was exceptional was that the Virginia earthquake was superimposed on the 21st century United States.

Geological and seismological perspectives aside, earthquakes are still always abrupt surprises in the popular sense. It is a common metaphor to compare the highly random aspects of exceptional earthquakes to throwing darts at a weighted map. It is clear, however, that the number and size of significant and sensitive targets on this map is steadily increasing. Illustrating this trend, 2011 offered a number of examples of novel infrastructural and societal surprises atop the scientific ones. Here are just a few examples. the tsunami-driven Tohoku-Oki earthquake failure of backup generators following electrical grid failure at the Fukushima-Daiichi complex initiated a cascade of engineering failures that resulted in the greatest accidental release of radiation since Chernobyl.

In an eerily similar scenario, ground motions from the modest Virginia earthquake exceeded design specifications for the North Anna nuclear power plant and produced a grid failure at the complex just 120 km upwind of Washington, D.C. Fortunately, and unlike Fukushima-Daiichi, North Anna successfully switched to its backup electrical generators (although one of the four failed to function). As a societal example of such unexpected consequences, consider the ongoing “Earthquake Trial” in L’Aquila, Italy. Apparently one week before the L’Aquila earthquake, offhand comments were made during an ad hoc press conference by (inappropriately, both at the time and in retrospect) to reassure the population. The subsequent tragic earthquake spurred unprecedented criminal and civil charges leveled by an angry and traumatized local population against both the misspoken government official and six Italian seismologist members of the associated advisory Major Risks Committee (who were not even present at the mismanaged press conference). The volatile legal atmosphere of post-L’Aquila Italy has understandably made many in the global seismological community anxious about potential exposure in a similar scenario (and speculating if natural or other societal disasters might represent fertile ground for future civil or even criminal actions; my suggestion to the lawyers would be to go after the economists first).

Recent unexpected and diverse effects and reactions following recent earthquakes have a common thread—we will have to increasingly expect the unexpected, not just in the context of the familiar randomness of seismicity itself but also in seismicity’s increasingly unpredictable social effects. Why is this so? There are a number of interrelated factors.

First, we are living in an increasingly interconnected world, where the flow of information and complexity of networks may be leading us toward potentially more chaotic responses to disruptive events. Recently increased volatility in the stock market fanned by vastly sped up trading, enhanced interconnectedness, reduced regulation, and more complex and interdependent (including, of course, in some cases fraudulent) investment instruments provides an illustrative example. Such trends are proceeding analogously in some sectors of infrastructure (the electrical grid is a classic example that is of great concern), government, media, and the broad economy. Managing the effects of such volatility is of course a complex interplay of the technical and the political worlds.

Second, populations in the hyper-connected world increasingly expect high-quality and near-immediate expert information at the same time that they are perversely more susceptible to easily disseminated inaccurate claims; a contributing factor to the L’Aquila debacle involved attempts to downplay a widely publicized radon-based indeterminate “prediction” that had alarmed residents.

In seismic and other natural hazards (including those being exacerbated by climate change), the potential for future disasters is compounded by the inexorable concentration and buildup of populations and infrastructure in cities, which puts vastly increased numbers of people at peril.

Third, a popular wave of dissatisfaction with governments and their (perceived or actual) competence is being widely rejected in increasingly skeptical (or worse) attitudes toward civil agencies and even toward their scientific staffs. These second and third issues point to the absolutely essential need for coordinated, respected, and authoritative sources of information.

Finally, in seismic and other natural hazards (including those being exacerbated by climate change), the potential for future disasters is compounded by the inexorable concentration and buildup of populations and infrastructure in cities, which puts vastly increased numbers of people at peril and can exacerbate all of the aforementioned factors (I would refer SRL readers who haven’t followed these sobering developments in some detail to read the superb “The Seismic Future of Cities” [Bilham 2009]). The increasing number of modern cities and megacities and their vulnerability to severe disruption by earthquakes has been recognized as a scenario for economic and social—as well as political—destabilization. The growth of megacities will dominate much of the natural hazards story throughout this century and beyond, and it is the factor that (probably) presents the greatest challenges to hazard mitigation efforts.

All told, we should expect that globally we will experience more such surprising (and even astounding) low-probability and potentially very high impact “Black Swan” events that will include unprecedented earthquake and post-earthquake scenarios (e.g., Taleb 2007). Seismologists are certainly going to have a busy future.    


Bilham, R. (2009). The seismic future of cities. Bulletin of Earthquake Engineering; doi:10.1007/s10518-009-9147-0. Taleb, N. N. (2007). The Black Swan: The Impact of the Highly Improbable. New York: Random House.

Richard Aster aster [at] ees [dot] nmt [dot] edu

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Posted: 27 December 2011