Scientists can not exactly predict any earthquake, but can tell a probable earthquake within a certain period of time, and a 30-second early warning is possible, said a US seismologist.

Margaret Vinci, manager of the Office of Earthquake Programs at the Seismological Laboratory in California Institute of Technology, told Xinhua in an interview Thursday that earthquake was hard to predict since each earthquake was different and the epicenters were underground.

She said all the earthquakes took place in a sudden, and researches so far had found no common signs to predict them.

However, the scientist said researchers could tell the probability of some major earthquakes. For example, she said, scientists had issued a warning that there would be a devastating earthquake in Southern California in the next 30 years, but it could happen tomorrow, and could happen in 30 years.

Vinci said that was called the probability, and not a prediction, because a prediction had to be exact, and the probability covered years or dozens of years.

Scientists tell the probability based on their research on past earthquake history and the movement of faults. There has been no strong earthquake over magnitude 7.8 in Southern California in the past 100 years, and based on the cycle of strong earthquake in the area, scientists can say there is a probability of another strong earthquake in 30 years.

However, according to Vinci, scientists can not tell the exact location the earthquake will take place. She said there were 300 faults in Southern California and those faults pushed against each other, causing different sizes of quakes.

She said in Southern California, there were 38 quakes a day on average, but most of them were very tiny and caused no damage. In most cases, people can not feel the quake.

Asked to comment why some earthquakes did happen as some researchers predicted, Vinci said real scientists did not make predictions. She admitted that there were people making such predictions, and if such a prediction turned out to be accurate, that was because of a good luck. This person might have made over 500 predictions and only one turned out to be true.

"That is a guess, not a prediction," she added.

However, the Caltech scientist said early warning had been made possible by using sophisticated instrument to monitor the actual happening of any strong earthquake.

Vinci explained that earthquake moved two miles a second, and most earthquake epicenters could be 20 or 50 miles underground. When instrument senses the movement, it can provide a warning 30 seconds or even 70 seconds before people can feel it.

She said scientists in her laboratory could provide an early warning of 30 seconds before the earthquake hit the ground. Those 30 seconds are very precious for human beings since they can make use of the 30 seconds to save lives.

She said elevators in tall buildings could stop operating to avoid further damages, and power plants could make use of the 30 seconds to shut off.

Vinci said the technology was ready, but to her regret, there was no such early warning system in the US She said it would cost US$100 million to set up such a system and hopefully the US government would provide funding for the program.

There are currently early earthquake warning systems in Japan, Mexico, Turkey, Romania and China's Taiwan.

Earthquake Alarm Systems take the form of a suite of algorithms designed to rapidly detect the initiation of an earthquake, determine the size (magnitude) and location of the event, predict the peak ground motion expected in the region around the event, and issue a warning to people in locations that may expect significant ground motion. The algorithms use data from regional broadband seismic networks.

(Xinhua News Agency April 16, 2010)