U.S. scientists are too pessimistic about a breakthrough in reliable earthquake predictions, according to two seismologists who are prominent in the search.
Writing on Thursday in the journal Science, Carnegie Institution seismologist Paul G. Silver and Tokyo University earthquake chemist Hiroshi Wakita say a recent meeting in Japan showed that the United States is lagging Japan and China in prediction research.
Silver has written previously about possible precursors to California earthquakes reflected in a Northern California geyser, and Wakita contended last year that he had found telltale changes in subterranean chlorine concentrations before Japan's devastating Kobe earthquake.
It is relatively uncommon for scientists to be openly critical in print of an entire scientific community.
But Silver and Wakita say that U.S. seismologists have not paid enough attention to promising developments elsewhere in the world that have shown changes in water or chemical levels occur in the months before important earthquakes.
Responding to the article, U.S. Geological Survey seismologist Lucy Jones said, "Compared to the rest of the world, we do less in prediction" but more in preparedness.
"Predictions might be less useful to us, because we have so much stronger building codes," she said. "If your building structure is resilient, then prediction isn't so necessary. It's most necessary where people are least prepared, such as in China.
"Would you rather have two hours notice of an earthquake, or buildings so strong they won't fall down when they occur?" she asked.
Silver and Wakita refer in their article to a magnitude 7.3 earthquake on July 11, 1995, along the Burma-China border, where they said advance variations in radon concentration, water level, water temperature and other phenomena led to an official prediction that "averted a substantial loss of life."
They also note recent progress at predicting quakes on California's San Andreas fault after water level anomalies are observed.
"Many pre-seismic signals are observed far from the impending earthquake, making it difficult to find a physical mechanism [as a cause]," Silver and Wakita say.
"And," they add, "the quality of studies in this field has been variable. Consequently, many researchers have dismissed precursory claims based on these data."
Reliable earthquake prediction has been elusive, they write, "gradually leading to strong skepticism, especially in the United States, about the prospects for prediction and even for detecting precursors.
"But this present pessimism . . . is probably excessive," they conclude, and they urge American scientists to expand observation programs to capture many more seismic events and build a reliable database.
In a 1995 conference on earthquake prediction in Irvine, Wakita created a stir by showing a graph on chemical changes in ground water recorded by an instrument at a Sake manufacturing plant on Rokko Island, just off Kobe in the 10 months before the Kobe quake.
Wakita said that during that time, the chlorine level rose from 13.3 parts per million of water to 15.4, and, then, when the magnitude 6.9 quake struck, the reading immediately sank to the earlier level.
But other scientists at the meeting discounted the finding's significance.
They said that it was just one case and that for precursory phenomena to be confirmed, it would be necessary to plot such patterns in many different locales and find out how often such increases were followed by a significant earthquake, and how often they were not.
"It's scientifically interesting, but it's not a practical predictive tool until one has enough information to assess the probability that an earthquake will follow," Jones said.