Scientists anxious about other big quakes

run through Haiti and the Dominican Republic. In 2008 a team of geologists figured out how much strain had built up in the southern fault responsible for this week’s quake, the Enriquillo-Plantain Garden fault, which stretches from Jamaica in the west through Haiti into the Dominican Republic. Using GPS tracking devices, they calculated that the plates had moved about 6 feet past each other since the last big earthquake in 1751, and they predicted that the fault had built up enough stress to produce a magnitude 7.2 earthquake.

Similar calculations have revealed other at-risk faults in other regions of the world.

The ancient Turkish city Istanbul, home to 12 million people, may be due for a massive earthquake in the coming decade. It lies only 12 miles from the North Anatolian fault, which has not ruptured since 1766 and has built up even more strain than the fault that caused the Haitian quake. “We would expect an even larger earthquake than the one in Haiti — the worst case scenario goes up to 7.6,” said seismologist Oliver Heidbach of the Helmholtz Centre Potsdam in Germany, whose research appears this Sunday in the journal Nature Geoscience.

The southern portion of the San Andreas fault near Los Angeles, quiet for 300 years now, has also accumulated enough strain to produce a “big one” of magnitude 7.0 or greater, according to University of California-San Diego seismologist Yuri Fialko.

The USGS maintains hazard maps highlighting areas of the United States considered to be most at risk for big earthquakes. The strongest U.S. earthquake ever recorded, magnitude 9.2, was the Great Alaska Earthquake of 1964. Now regions in South Carolina and Washington state are considered at risk, and particular attention is being paid to the New Madrid fault — which runs through Missouri and six other Southern and Midwestern states. The last time this fault ruptured, in 1811, the vibrations were said to have caused church bells to ring as far away as Boston


Quakes beget quakes

ISNS reports that during the Haitian quake, only 30 to 60 miles of the 300-mile fault near Port-au-Prince ruptured and slid. The rest of it stayed stuck, still glued together by friction. The area that ruptured is likely to have increased the amount of strain — and the risk of quake — in other parts of the fault, especially in areas to the west of Port-au-Prince.

This happened in 2004 in Indonesia, after a magnitude