Recent earthquake activity in China was not forecast. Image courtesy of USGS.
An earthquake which struck in western China on 12 February 2014 is just another in a series of inevitable natural disasters; events which we can expect but not forecast. But this week’s earthquake calls to mind another, in 1975, which authorities did successfully predict – and as a result, remarkably few lives were lost.
The Haicheng Earthquake of 1975
On 4 February 1975, the authorities in Haicheng, China, announced that a major earthquake was imminent and began an evacuation of many thousands of people from what they considered vulnerable areas.
When an M7.0 earthquake struck later that day, it devastated much of the city of Haicheng and its surrounding region. In spite of this devastation, the death toll of just over 2,000 people was far lower than the estimated 150,000 who otherwise might have died or been injured, according to United States Geological Survey (USGS) Historic Earthquakes.
The exact details of the prediction included complicated parts and drew on extensive data. In their exhaustive consideration of the process, Kelin Wang and his colleagues Qi-Fu Chen, Shihong Sun and Andong Wang identified certain key stages; specifically that there were two medium-term predictions based upon a series of foreshocks. Scientists also took account of other potential earthquake precursors, such as changes in ground water levels, ground deformation and even animal behaviour.
Scientists predicted the Haicheng earthquake of 1975, but not this quake, which struck the following year. Image courtesy of the NOAA.
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On the face of it, the attempt at prediction was an unprecedented success. As Wang and his colleagues put it, “the prediction of the Haicheng earthquake was a blend of confusion, empirical analysis, intuitive judgment, and good luck, it was an attempt to predict a major earthquake that for the first time did not end up with practical failure.” But was it the breakthrough it appeared?
In one sense, it certainly was. But earthquakes do not play by human rules; the following year, also in China, another earthquake of M7.5 struck China. This time there was no warning, no observed precursors; and the death toll, which is unclear, may have exceeded 650,000
Earthquake Prediction: The Seismologists’ Holy Grail
The Haicheng prediction shows the value, in terms of human life if not of property, of a foolproof method of predicting earthquakes. But, given that we know with some certainty where in the world tremors will occur, broadly how large we expect them to be and that they will occur regularly, the science of earthquake prediction remains poorly developed.
The public (and in some cases, prosecutors) expect that scientists will be able to tell them when and where an earthquake will occur. Seismologist Roger Musson, in his book The Million Death Quake, remarked rather ruefully that, “Back in the 1960s it was routinely assumed that earthquake prediction was just around the corner.” Unfortunately it hasn’t turned out that way.
The Parkfield earthquake of 2004 came years later than expected. Image courtesy of the USGS.
In 1981, a prediction by American Brian Brady that a “magnitude 7.5–8.0 event would occur [in Lima, Peru] on or about June 28, followed by a magnitude 9.2 event (Kanamori scale) on or about August 10, and a magnitude 9.9 event on or about September 16,” came to nothing, and as Barbara T. Richman points out, the erroneous prediction caused economic and social problems in the run up to the disaster which never came.
A few years later, the USGS supported an ambitious experiment in the town of Parkfield, California, where a series of earthquakes of similar magnitudes, led to the prediction of an earthquake of around M6.0 between 1985 and 1993. The earthquake duly came… 11 years late.
Current State of Quake Prediction
Seismologists are still working on the prediction of earthquakes but it’s a double-edged sword. The problems of false alarms – evacuating in preparation for a disaster which doesn’t occur – can cause a loss of trust in the prediction process and have economic implications of their own. The truth is that earthquakes and their processes continue to surprise us.
Studies of potential precursors, such as changes in groundwater levels or seismic activity, continue. But as Haicheng and its more deadly successor clearly demonstrate, what’s true for one earthquake may not be true for another; some have a series of foreshocks and some strike with no warnings at all.
February 2012 China Quake: Unpredicted
The February 2014 tremor in western China, as far as we are aware, was not forecast and killed no-one. But the cost of earthquakes in death, damage and dollars (it’s estimated that economic losses from the 2010 Haiti earthquake, for example, amounted to $7.74 billion) is so great that a successful prediction strategy is highly desirable – and seismologists continue to seek it.
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