Haiti's devastating earthquake -- and its horrific human toll -- caught many by surprise. But there are more little-noticed hot seismic hot spots across the globe. Here are five places that geologists worry could be the next big one.
UNITED STATES, LOWER MISSISSIPPI DELTA REGION
Fault Line: New Madrid
Last big quake: 1812
Reasons to worry: A string of earthquakes in the early 19th century along the New Madrid fault -- covering parts of Illinois, Missouri, Arkansas, Kentucky, Tennessee, and Mississippi -- caused the Mississippi River to flow backwards, rang church bells in Boston, and affected an area more than three times as large as the famous San Francisco quake of 1906.
Two hundred years ago, the at-risk population was minimal. Today, the major cities of Saint Louis and Memphis lie within the danger zone of arguably the United State's most threatening fault line. FEMA warned in 2008 that a major New Madrid fault earthquake could cause "the highest economic losses due to a natural disaster in the United States," largely due to a relative lack of earthquake preparation compared with California and the Pacific Northwest.
Fault line: North Anatolian
Last big quake: Duzce, 1999
Reasons to worry: The 1999 earthquake in Izmit -- located off the Sea of Marmara, and just southeast of Istanbul -- killed nearly 18,000 people. Izmit was the latest in a series of quakes that struck westward across Turkey over the last 70 years. A quake only three months later in Duzce killed close to 900. In the last four decades, Turkey has suffered more than six earthquakes with more than 1,000 fatalities.
More frighteningly, scientists say the next quake is likely to break slightly west of Izmit -- and directly south of Istanbul, a city of 12 million people. The seismic buildup is likely to result in a few smaller events, rather than a single mega earthquake -- but that's little comfort to the residents one of the world's oldest and most historically important cities.
Fault line: in between the Pacific, Philippine, and Eurasian plates
Last big quake: Newcastle, 1989
Reasons to worry: Unlike the other countries on this list, Australia does not actually lie along a fault line between two tectonic plates -- that is, it's an intraplate location, which is hardly cause for comfort. Australia's seismic activity is the result of plate pressure far from the continent itself, which means that literally any part of Australia is under potential threat and the country's quakes are extremely difficult to predict.
Luckily, most Australian quakes, including 10 in 2008 with a magnitude greater than 4.0, have struck in the barren center of the country, causing minimal damage. But the unpredictability of seismic bursts has led to a false sense of security -- building materials in major cities like Sydney are old, corroded, and vulnerable, as evidenced a by relatively minor 5.5 magnitude 1989 Newcastle earthquake that caused more than U.S. $1.4 billion in damage. A quake near Sydney, which has a population 15 times greater than Newcastle, would be far more deadly.
Fault line: Himalayan Frontal Thrust, Main Boundary Thrust, Main Central Thrust
Last big quake: 1988, Nepal-India border region
Reasons to worry: Just south of the Himalaya Range, and only 150 miles southwest of Mt. Everest, the Nepalese capital of Kathmandu is right on the border between the Indian and Eurasian plates. Despite there being no major earthquakes in the area in recent years, geologists warn that the numerous faults along the Himalayas put the Nepalese capital at risk of a massive seismic event.
Worse, Nepal's earthquake preparedness is dismally low, thanks to poor construction methods and a rapidly increasing urban population. The lack of recent earthquake activity is actually another cause for concern -- typically, the longer the length between quakes, the more likely the next one will be especially powerful. Like Haiti, Nepal has been wracked by recent political turmoil. A 10-year civil war ended in 2006, and political stability and economic development since then have been minimal, hampering the authorities' ability to prepare for a natural disaster.
Fault line: Median Tectonic, Itoigawa-Shizuoka Tectonic, Tanakura Tectonic
Last big quake: Great Hanshin-Awaji, 1995
Reasons to worry: Japan is a more well-known earthquake spot due to catastrophic events like the 1995 Great Hanshin-Awaji earthquake, which killed 6,400 people. Luckily, Japan's experience with earthquakes has led it to invest significantly in preparedness and quake-resistant infrastructure, but this should not lead to a false sense of security.
Japan remains at risk because of its extremely densely packed cities -- if a big quake were to directly hit megacities like Tokyo or Kyoto, studies show that casualties could potentially kill upwards of 60,000. The Great Kanto quake of 1923 killed well over 100,000. Furthermore, earthquake activity off the coast of Japan leaves the country vulnerable to tsunamis. Japan's heavy reliance on nuclear power is another cause for concern, particularly after a 2007 quake caused a dangerous leak at a plant in Kashiwazaki.
Ronald Martinez/Getty Images; AFP/Getty Images; Brendon Thorne/Getty Images; PRAKASH MATHEMA/AFP/Getty Images; JIJI PRESS/AFP/Getty Images