SANTA CRUZ, Calif. -- Mexico City usually pays the heaviest price when earthquakes strike Mexico because of high activity along several faults and a geological quirk that makes the city especially vulnerable, an expert says.
'Mexico City sits in a high sedimentary basin, which amplifies the ground shaking like a bowl of jelly,' said Karen McNally, director of the Charles Richter Seismological Laboratory and a professor of geophysics at the University of California-Santa Cruz.
'In addition, of course, it is a very large population center with lots and lots of construction,' she added Thursday.
She noted Mexico has suffered more than 30 extremely powerful temblors (7.5 or more on the Richter scale) in the past 60 years. The latest major quake struck Thursday and registered 7.8 on the Richter scale. Hundreds of lives were lost, apparently mostly in Mexico City.
'Mexico has roughly five times as many large earthquakes as we do in California,' McNally said. 'The faults are slipping more rapidly and the fault zone is wider.'
But she noted that the United States is always in danger of an equally severe temblor. 'A large earthquake of 7.5 or greater might be expected reasonably at any time, particularly in the southern California area. One 6.5 to 7 is equally likely in the northern California area within the current time frame of maybe two or three years.'
Mexico has active volcanos as well as many earthquakes, making it as 'tectonically active' as Central America, the Pacific Coast of South America, Alaska and Japan, McNally said.
Asked what Mexico can do do cut down its quake damage, she said, 'Mexico can't prevent earthquakes. A good, enforced earthquake code would be important.'
She said the current Mexican codes are weak and are 'not uniformly enforced and not very rigid. In addition, plans for emergency response are important.'
