A massive earthquake struck Haiti just before 5 p.m. on Jan. 12, about 10 miles southwest of Port-au-Prince, the country's capital. The quake was the worst in the region in more than 200 years, and as many as 50,000 people were feared dead.
The quake left the country in shambles, without electricity or phone service, tangling efforts to provide relief. Governments and private groups from Beijing to Grand Rapids pledged assistance, but two days after the quake only the barest trickle of aid had arrived.
The day after the quake, Haiti's president, René Préval, called the destruction "unimaginable.''
On Jan. 14, Secretary of State Hillary Rodham Clinton said that "there will be tens of thousands of casualties - we don't have any exact numbers." She said that about three million people -- a third of the country's population -- had been affected.
The earthquake could be felt across the border in the Dominican Republic, on the eastern part of the island of Hispaniola. High-rise buildings in the capital, Santo Domingo, shook and sent people streaming down stairways into the streets, fearing that the tremor could intensify.
More than 30 significant aftershocks of a 4.5 magnitude or higher rattled Haiti through the night of the 12th and into the early morning, according to Amy Vaughan, a geophysicist with the United States Geological Survey.
Huge swaths of the capital, Port-au-Prince, lay in ruins, and thousands of people were feared dead in the rubble of government buildings, foreign aid offices and shantytowns. Schools, hospitals and a prison collapsed. Sixteen United Nations peacekeepers were killed and at least 140 United Nations workers were missing, including the chief of its mission, Hédi Annabi. The city's archbishop, Msgr. Joseph Serge Miot, was feared dead.
The poor who define this nation squatted in the streets, some hurt and bloody, many more without food and water, close to piles of covered corpses and rubble. Limbs protruded from disintegrated concrete, muffled cries emanated from deep inside the wrecks of buildings - many of them poorly constructed in the first place.
On Jan. 13, as Ban Ki-Moon, the secretary general of the United Nations, warned of a humanitarian disaster, President Obama promised that Haiti would have the "unwavering support" of the United States.
But while world leaders pledged hundreds of millions of dollars and thousands of troops, delivering on these promises was a logistical nightmare. On Jan. 14, aid was arriving only in a trickle to those thought to need assistance.
Power was still out and telecommunications rarely functioned. Most medical facilities had been severely damaged, if not leveled. Supplies of food and fresh water were dwindling. Ships could not bring their cargos of supplies into Haiti's damaged port; the airport was functioning with severe limits; roads were blocked not only by debris but also by people with no safe shelter to retreat to.
Mr. Obama said that United States aid agencies were moving swiftly to get help to Haiti and that search-and-rescue teams were already en route. Mr. Obama did not make a specific aid pledge, and administration officials said they were still trying to figure out what the island needed. But he urged Americans to dig into their pockets and to go to the White House's Web site, www.whitehouse.gov, to find ways to donate money.
Aid agencies from around the world geared up to help. Agencies already in Haiti said they would open their storehouses of food and water there, and the World Food Program was flying in nearly 100 tons of ready-to-eat meals and high-energy biscuits from El Salvador. The United Nations said it was freeing up $10 million in emergency relief funds, the European Union pledged $4.4 million, and groups like Doctors Without Borders were setting up clinics in tents and open-air triage centers to treat the injured.
Supplies began filtering in from the Dominican Republic, as charter flights were restarted between Santo Domingo and Port-au-Prince. But efforts to administer emergency services and distribute food and water were halting, and in some places seemingly nonexistent. A few S.U.V.'s driven by United Nations personnel plied streets clogged with rubble, pedestrians and other vehicles. Fuel shortages emerged as an immediate concern as motorists sought to find gas stations with functioning fuel pumps.
Earthquakes in the Caribbean
Haiti sits on a large fault that has caused catastrophic quakes in the past, but this one was described as among the most powerful to hit the region.
The Caribbean is not usually considered a seismic danger zone, but earthquakes have struck there in the past.
"There's a history of large, devastating earthquakes," said Paul Mann, a senior research scientist at the Institute for Geophysics at the University of Texas, "but they're separated by hundreds of years." Most of Haiti lies on the Gonave microplate, a sliver of the earth's crust between the much larger North American plate to the north and the Caribbean plate to the south. The earthquake on Tuesday occurred when what appears to be part of the southern fault zone broke and slid.
The fault is similar in structure to the San Andreas fault that slices through California, Dr. Mann said.
Such earthquakes, which are called strike-slip, tend to be shallow and produce violent shaking at the surface.
"They can be very devastating, especially when there are cities nearby," Dr. Mann said.
David Wald, a seismologist with the Geological Survey, said that an earthquake of this strength had not struck Haiti in more than 200 years, a fact apparently based on contemporaneous accounts. The most powerful one to strike the country in recent years measured 6.7 magnitude in 1984.
Social Conditions in Haiti
Haiti is known for its many man-made woes - its dire poverty, political infighting and proclivity for insurrection.
The country is, by a significant margin, the poorest in the Western Hemisphere, with four out of five people living in poverty and more than half in abject poverty. Deforestation and over-farming have left much of Haiti eroded and barren, undermining subsistence farming efforts, driving up food prices and leaving the country even more vulnerable to natural disasters. Its long history of political instability and corruption has added to the turmoil.
The United States and other countries have devoted significant humanitarian support to Haiti, financing a large United Nations peacekeeping mission that has recently reported major gains in controlling crime. International aid has also supported an array of organizations aimed at raising the country's dismal health and education levels.
Since 2008, the country's situation has worsened dramatically, as it faces food riots, government instability and a series of hurricanes that killed hundreds and battered the economy.
Hurricanes Gustav, Hanna and Ike and Tropical Storm Fay landed within the space of a month in August and September 2008. The four storms flooded whole towns, knocked out bridges and left a destitute population in even more desperate conditions. Nationally, damages came to a total of $900 million, or nearly 15 percent of the gross domestic product. The national toll was 800 dead.
How to Help
Cell phone users can text "Haiti" to the number 90999 and donate $10 to the Red Cross. The amount will be added to the donor's cellphone bill. Other organizations have set up similar systems. Text "YELE" to 501501 to donate $5 to Yele Haiti.
Medical organizations based in Haiti before the quake are struggling to cope with its aftermath. Doctors Without Borders reports it has treated more than 1,000 people on the ground and has appealed for support. Partners in Health, a major non-governmental health care provider in Haiti, operates clinics in Port-au-Prince and is also soliciting donations.
The Times' Lede blog has posted a list of various charity organizations that plan to provide relief.