>A 7.1 magnitude earthquake struck Western China this morning, killing over 400 people and injuring at least 10,000. The quake is the latest in a string of fatal tremblers this year: Haiti in January, Chile in February, Taiwan in March, and Mexico just last week. It may be easy to suspect some sort of connection among the disasters, or to wonder if we're experiencing more frequent or powerful quakes than we have before.
Seismologists, however, are quick to dispel such presumptions. Since 1900, the U.S. Geological Survey has recorded a yearly average of nearly 1.5 million earthquakes. The large majority are not felt, but the number of quakes that reach a magnitude of 7.0 or greater has stayed relatively steady -- if anything, it's decreased. The USGS expects about 18 major earthquakes (7.0-7.9) and one great earthquake (8.0 or higher) per year. Since 1971, we have only reached or exceeded this expectation four times. Though we've seen four serious earthquakes already this year, only Chile measured 8.0 or above.
In a Q&A with Washington Post readers, USGS geophysicist Michael Blanpied noted that quakes that would previously have gone unnoticed are now picked up by better seismic technology and publicized through internet news reports. Big quakes are also likely to affect larger numbers of people than they used to thanks to population growth and urban development.