Science & Seismology 
Along the New Madrid Seismic Zone

   The word science derives from the Latin, meaning "to know." But as we enter a new century, there are reminders about what science has yet to learn.

    The Mars Polar Lander disappeared last December, minutes from touchdown, showing that certain parameters of space still resist the grasp of scientific understanding. There are examples closer to Earth, such as "why haven't we managed to cure the common cold?"

    And there is a major example of the limits of knowledge beneath the surface of the central United States.

    The New Madrid Seismic Zone spans the central Mississippi Valley, stretching from Illinois to Arkansas, winding through Missouri and nearby western Kentucky and Tennessee. Three of the largest earthquakes in U.S. history occurred along the New Madrid in the early 1800s, with main shocks exceeding 8.0 Richter magnitude. The fault has been relatively quiet lately, but it continues to produce several "micro-quakes" each year. Only a few of these category-ones and -twos are felt above ground.

    Much has been learned about the zone over the past several decades, including an understanding of its destructive potential. Civil engineers with the Central U.S. Earthquake Consortium estimate that a serious quake could kill thousands and cause more than $50 billion in damage, much of it in cities from St. Louis to Memphis, and deeply impacting Paducah and other Ohio River communities.

    But while seismology is sure about what can happen, its estimates of when remain highly probabilistic. The U.S. Geological Survey reports a 50 percent chance of a Richter magnitude 6.0 along the New Madrid over the next 15 years, and a 90 percent chance by 2050. (Similar-sized quakes in Eurasia have wrought heavy destruction, while a category-six temblor in California killed five dozen people in the 1990s).

   Can't science predict these quakes?

    Jim Devine, senior advisor for scientific applications at U.S.G.S., says that short-term earthquake prediction techniques in North America are constantly evolving, but that geoscience is constrained along the New Madrid, where the lack of a recent "major event" has left too little data.

    "We are not at the stage of accurate forecasting days or months in advance, and many of our scientists are beginning to believe that we may never be," Devine says.

    U.S.G.S. geophysicist Lucille Jones argues that it may be impossible to forecast serious earthquakes in the short term. "The difference between a common small earthquake and a damaging one is not in how it starts, but in how it stops," she says. "And the process is dynamic, one factor of ground motion affecting every other. To tell how significant they are before they're under way may be theoretically unknowable."

    Geophysicists don't agree about when -- or if -- they will be able to bank on valid forecasting, according to Devine, "but it's clear we'll never be telling you that 'the fault is ready to go next Tuesday at three o'clock.'"

    In other words, predictions about the New Madrid during our lifetimes will likely take the form of intermediate-term probabilistic estimates. Instead of a "percent chance" over 15 or 50 years, we'll hear a probability percentage spanning eight years or less. The time window could shorten as techniques become more robust.

    The physical forerunners to major quakes are called "precursors," or premonitory events. Detection and evaluation of precursors has proven difficult, but these indicants can include "ground creep"; changes in water levels; and deformation of underground rocks. According to geophysicist Robert Herrmann of St. Louis University's Earthquake Research Center, technology now under development in the oil industry -- such as crustal imaging -- may soon add to the seismologist's toolkit, enhancing recognition of precursors.

    If precursors were detected along the New Madrid, what would the public find out and when? Given the potential impact of a scientifically endorsed prediction, would the public even be notified?

    The experts are aware of the social and economic implications of earthquake prediction in the short- to intermediate-term (weeks to a few years in advance). Scientists say the bottom line of public information is addressed by both ethical and practical concerns: If the New Madrid shows signs of activity, seismologists would have to say so publicly because it is right; and also because their own credibility and integrity would be at stake. This according to experts at the core of decision-making, like U.S.G.S. geophysicist Joan Gomberg, a field officer in Memphis: "We agree that we could not sit on such information."

    But Gomberg says that scientists may offer differing opinions on the significance of premonitory events. This would complicate -- and possibly delay -- the issuance of public warnings.

    A cynic would appreciate the view of Richard Stuart Olson, author of the 1989 book, The Politics of Earthquake Prediction. Olson notes that disputes within the scientific community are often tempered by a "prevailing consensus," which discourages risky or divergent judgments. Geoscience is like other social orders, he says, maintaining "an orthodoxy that seeks to control conflict" within the field.

    But most scientists cite functional, not political, concerns: "We must be aware of Chicken Little 'the-sky-is-falling' situations," says Arch Johnston, Director of the Center for Earthquake Research and Information (CERI) in Memphis. "We might be off in our assessments, and have to wonder, what is the acceptable rate of false alarms? When does informing people of probable risk outweigh the degree to which people might become complacent in the face of future warnings?"

    So many questions about the New Madrid remain unanswered, says Neil Weber, chair of the Geosciences Department at Murray State University, that "there's more that we don't know than what we do." The documented history of tremors in the region, he says, doesn't go back far enough to establish accurate "recurrence intervals" within which quakes of known sizes could be expected to happen again.

    There are always an appointed handful of scientists on call in mid-America, a type of 24-hour "beeper patrol" that extends to U.S.G.S. officials in Colorado and Virginia. If significant precursors were identified or foreshocks measured, various research centers would receive teleseismic observations. Local experts would be consulted, perhaps including those from academic geoscience units in Kentucky, Tennessee, Missouri and Illinois. They would evaluate the meaningfulness of events or predictions, and decide on notification of the Department of the Interior; the White House; and governors of perhaps a dozen states in the heartland.

    Federal "Department Emergency Notification System" (DENS) guidelines suggest means of alert and procedure, which would pull emergency management officials into long-distance conference. Federal, state and local safety officials stress the importance of their being notified in advance of news media, this so they "understand the story" before having to explain it publicly.

    What about legal liability in the event of a forecast quake that didn't arrive? Agencies might rely upon so-called "Good Samaritan" legal statutes and indemnification protections if businesses file civil lawsuits alleging damage. The larger question -- about the economic consequences of essentially shutting down the Midwest on the heels of a scientifically endorsed warning -- hasn't yet caused much sleep loss among scientists.

    But as knowledge increases, seismologists may share the quandary of geneticists, who only recently have had to face more questions than they bargained for. A scientific epiphany in the lab today can lead to piercing moral dilemmas tomorrow, such as: "what do we say about our discovery, and when and how do we say it?"

    For now, it would seem, the axiom Space: the final frontier could be rewritten to substitute the word Earth. As it regards earthquake prediction, the New Madrid fault still qualifies as an enigma of science. But that will be less true as time goes on, and science needs to focus its attention on what that will mean for public policy in the 21^st Century.