Predicting Earthquakes

Never before have so many people packed into cities –places such as Los Angeles, Istanbul,Tokyo, and Lima- that are regulary affected by earthquakes. Located near the edge of Earth´s huge, shifting plates, these cities face the risk of death and economic disaster from large quakes – and from the tsunamis, fires, and other destruction they often cause.

We understand earthquakes better than we did a century ago. Now, scientists would like to predict them, but is this posible? Today, some of the simplest questions about earthquakes are still difficult to answer: Why do they start? What makes them stop? Perhaps the most inmportant question scientists need to answer is this: Are there clear patterns in earthquakes, or are they basically random and imposible o predict?

In Japan, government scientists say they have an answer to the question “We believe that earthquake prediction is posible” says Koshun Yamaoka, a scientist at the Earthquake Research Institute at the University of Tokyo. Earthquakes follow a pattern; they have observable signd, Yamaoka believes. In fact, Japan has already predicted where its next great earthquake will be: Tokai, a región along the Pacific coast about 161 kilometers (100 miles) southwest of Tokyo. Here, two plate boundaries have generated huge earthquake every 100 to 150 years. But the section along Tokai hasn´t had a major quake since 1854. The theory is that strain is building up in this región, and that it´s time for this zone to reduce its stress. Unfortunately, this is more a forecast prediction. It´s one thing to say that an earthquake is likely to happen in a high-risk área. It´s another to predict exactly where and when the quake will occur.

The desire for a precise prediction of time and place has lead to another theory: the idea of “preslip”. Naoyuki Kato, a scientist at the Earthquake Research Institute, says his laboratory experiments show that before a fault in the Earth´s crust finally breaks and causes an earthquake, it slips just a little. If we can detect these early slips taking place deep in the Earth´s crust, we may be able to predict the next big quake.

Scientists working in Parkfield, California, in the U.S. are also trying to see if Predicting earthquakes is posible. They´ve chosen the town of Parkfield not only because the San Andreas Fault runs through it, but because it´s known for having earthquakes quite regulary ­– approximately every 22 years. In the late 1980´s, scientist in Parkfield decided to study the fault to see if there were amy warning signs prior to a quake. To do this they drilled deep into the fault and set up equipment to register activity, Then they waited for the quake.

Year after year, nothing happened. When a quake did finally hit on September 28, 2004, it wads year off Schedule, but most disappointing were the lack of warning signs. Scientists reviewed the data but could find no evidence of anything unusual preceding the September 28th quake. It led many to believe that perhaps earthquakesreally are random events. Instead of giving up, though, scientists in Parkfield dug deeper into the ground.

By late summer 2005, they had reached the fault´s final depth of three kilometers (two miles), where they continued collecting data hoping to find a clue.

And then they found something. In an article published in the July 2008 journal Nature, the researchers in Parkfield claimed to have detected small charges in the fault shortly before an earthquake hit. What had they noticed? Just before a quake, the cracks in the fault had widened slightly. Scientists registered the first changes ten hours before a 3.0 quake hit; they identified identical signs two hours before a 1.0 quake – demostrating that perhaps the “pre-slip” theory is correct. In other words, it may in fact be posible to predict an earthquake.

Although there is still a long way to go, it appears from the research being done all over the world that earthquakes are not entirely random. If this is so, in the future we may be able to track the Earth´s movements and design early-warning systems that allow us to predict when a quake will happen and, in doing so, prevent the loss life.

SOURCE: Reading Explorer 3. HEINLE CENGAGE Learning, National Geographic 2010