LOS ANGELES (CBSLA.com) — Tuesday’s powerful 7.1 magnitude earthquake in Mexico caused death, injuries and serious structural damage. What kind of damage would a quake of the same magnitude cause if it happens in the Los Angeles area?

U.S. Geological Survey seismologist Lucy Jones explained the difference.

“Mexico City is built on a dry lakebed. So there was a lake there. It dried out and left behind the sediments that are very very loose. Here in downtown Los Angeles, we have about a factor of five amplification because of soils, and Mexico City is over a factor of 100. So they have damage from earthquakes 100 miles away,” Jones explained.

There were also questions about why the much stronger 8.2 quake off the coast of Oaxaca, Mexico on Sept. 7 didn’t cause nearly as much damage or loss of life.

“This earthquake is smaller, but it’s closer to many more people. So where the 8.2 was offshore and at a depth of 40 miles down. This is only 80 miles from Mexico City and about 30 miles down with a lot of people nearby. Proximity makes a big difference,” Jones said.

After Monday night’s 3.6 magnitude jolt was felt on the Westside, fears led people to wonder if Mexico’s latest quake was connected.

“The 3.6 yesterday is a size that happens somewhere in the world many times per hour. The only thing that made it newsworthy that it was under the Westside of L.A. and a lot of people commented on it,” the seismologist added.

  1. The obvious question arising out of this quake is how did Mexico City’s “early warning” system perform when a quake was not 300 miles away but relatively nearby? The USGS many times has mentioned this Mexican early warning system as justification for building its own.

    However, Mexico City residents clearly did not get any usable warning this time. In California, the worst damage from a strong quake typically occurs much closer to the epicenter. That severely limits the utility of “early warning” systems, which depend on electronic warning to outrace the damaging vibrations.

    The rising death toll in Mexico argues forcefully for the United States to go beyond early warning and bring online electromagnetic earthquake forecasting technologies, which can deliver forecasts days and even weeks in advance.

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