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This article is from the In-Depth Report An Essential Guide to the U.S. East Coast Earthquake
60-Second Earth

Earthquakes Exert Global Influence

An earthquake in Indonesia can mean future tremors in California. David Biello reports

[The following is an exact transcript of this podcast.]

A powerful earthquake beneath the Pacific triggers a tsunami that devastates Samoa and American Samoa. Another powerful temblor strikes off the coast of Sumatra. But is there a connection beyond the fact that both sit on the geologically active Ring of Fire that encircles the Pacific Ocean? 

According to new research published in Nature this week: yes. 

U.S. seismologists looked back at powerful earthquakes of the past, such as the 2004 seismic event off Sumatra that spawned a killer tsunami throughout southeast Asia. That earthquake, the second largest ever recorded, had a discernible impact on the San Andreas fault half a world away. 

Earthquakes occur when such faults slip due to weakness or stress. But measuring fault strength has not been possible in the past.  

By looking back at the seismic record for the San Andreas fault near Parkfield, Calif., the "Earthquake Capital of the World," the seismologists found that an increase in microquakes there corresponded with subtle shifts in subterranean fluids between 1987 and 2008. 

Two of these shifts followed nearby earthquakes—within 200 miles—and boosted the number of tiny quakes. But the third shift occurred after the Sumatran quake in 2004. 

That means a new way to predict quakes in future and the possibility that this week's earthquake-related tragedies could strike on the other side of the Pacific, as well. 

—David Biello

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