The well-known Enriquillo fault was quickly blamed, but new data revealed a more complicated picture. "Because this is a blind fault, we don't have some of the clues at the surface, like scars from past ruptures, that show where the fault runs.

The Enriquillo-Plantain Garden fault zone (EPGFZ) had not produced a major earthquake in recent decades. the Léogâne fault, as inferred from previous slip inversions, but with two subfaults, each corresponding to a major slip patch.

"Those were the two important smoking guns" that made scientists question their early assumptions about the quake, says Eric Calais, a Purdue University geologist who is in Haiti as a science adviser to the U.N. Development Program and is a lead author of the study, which was published last month in Nature Geoscience. Globally, 3 percent of tsunamis are caused by slides.

. (See more about the January earthquake that devastated Haiti. ScienceDaily. Geologists like Amelung's Miami colleague, Tim Dixon, began to identify the Enriquillo fault as a major Caribbean quake hazard in the 1980s. On the Enriquillo fault you can almost walk the line of the fault because scars from many past events reveal the fault below.

Interpretation of our various seismic data sets has indicated prolonged sedimentary environments of fluvial channeling and channel migration to a depth of approximately 350 m as expected in this fan delta setting. A survey of 52 buildings in nearby Léogâne found that more than 90 percent had either collapsed or will require repairs. We considered two possible slip models, the simple single-fault slip model proposed by Calais et al. ScienceDaily, 26 October 2010.

"This makes it much more difficult to predict.". Haiti's Cholera Riots: A Plot to Stop the Elections?

Purdue University. To geologists, it's good to see Haitians on such heightened alert.

Questions? We resolve CFS changes on the Léogâne rupture plane itself, as well as on regional faults such as the Enriquillo, Neiba-Matheux, and Trois Baies faults. "This means that the Enriquillo fault is still capable of producing large earthquakes and that Haiti has to adapt to this seismic hazard," said Calais, who in September was appointed science adviser for the United Nations Development Program in Haiti.

Purdue University. For the Trois Baies fault, located to the northwest of the rupture between the Gonâve island and the Southern Peninsula and striking N120°, we find a modest CFS increase (~0.1 bar) on the shallow portion of the segment and a ~0.5 bar CFS increase on the deeper portion.

In Haiti, slide-triggered tsunamis may be 30 percent more frequent, Hornbach said. Both slip models imply a ~1 bar increase of CFS bar on the Enriquillo fault to the west and east of the January 2010 rupture. That's largely because they've found, according to a new study by 10 prominent geologists, that the lion's share of the January temblor occurred not along the fault line they originally suspected, known as the Enriquillo–Plantain Garden fault zone, but on a previously unknown fault. That isn't the case with the Léogâne fault.". "It was a surprise," said Susan Hough, of the U.S. Geological Survey (USGS) in Pasadena, Calif., who studied the Haiti earthquake "It's a ridge in an affluent part of the city, and it really got hammered.". Tsunami triggerJust as surprising as the complexities of the quake is that it triggered several small tsunamis.

Materials provided by Purdue University. The Léogâne fault, which cannot be observed at the surface, descends northward at an oblique angle away from the EPG fault system, and many geologists contend that the earthquake resulted from the…. More important, it's another reminder that Haiti has to rebuild smarter — the quake's death toll could have been slashed if the country hadn't allowed so much shoddy concrete construction and poor urban planning — so that when the next big quake does hit places like Carrefour, Haitians can escape horrors like those of January 2010. It is not intended to provide medical or other professional advice.

The damage was estimated at about $8 billion, according to Munich Re, the world's largest insurer. Scientists later discovered that the earthquake's energy spread in an unusual way — it was significantly amplified along this mountain ridge, causing substantial structural damage. "This was such a big surprise that I thought all our calculations were wrong.".

Andrew Freed, paper co-author and a Purdue professor of earth and atmospheric sciences, said the absence of any surface rupture was the first clue that the earthquake did not happen along the Enriquillo fault. The team analyzed data they recorded before the Jan. 12 earthquake and new measurements taken after the event.

It's still sitting on a [seismic] time bomb that Haiti had unfortunately ignored before Jan. 12, and which we and the Haitians now have to focus on more closely."

The team plans to continue to take measurements of the postseismic processes that allow them to understand changing stresses within the Earth's crust over time that could help point to areas where seismic hazard is increasing. The Haiti quake, however, triggered massive underwater landslides that, along with a small amount of ground motion, made the waves, Hornbach said. The 120  km2 Léogâne fan delta in southwestern Haiti borders the epicentral region of the devastating magnitude 7.0 Haiti earthquake of 12 January 2010. Carol Prentice, a geologist with the USGS, explains observations made by her team of geologists to children near Beloc, Haiti who experienced the 2010 earthquake firsthand.

It was performed in collaboration with, and in support to, the Haitian National System for Disaster Risk Reduction. Purdue University. Views expressed here do not necessarily reflect those of ScienceDaily, its staff, its contributors, or its partners. …by contractional deformation along the Léogâne fault, a small hidden thrust fault discovered underneath the city of Léogâne. And, perhaps most important, why did so little of the Enriquillo fault itself seem to rupture? Léogâne (Haitian Creole: Leyogàn) is one of the coastal communes in Haiti.It is located in the eponymous Léogâne Arrondissement, which is part of the Ouest Department.The port town is located about 30 km (19 mi) west of the Haitian capital, Port-au-Prince.Léogâne has a rich and unique culture, especially with regard to the arts, music, literature, cuisine, and architecture. "But we can use this for hazard assessment and say this region has a high likelihood of a large earthquake, and plan for whatever we're building in this region.".

Usually, a fault that moves up and down will move the seafloor and produce massive waves; strike-slip fault systems slide side-to-side when two plates butt heads. There was no clear evidence on our seismic reflection lines for substantial faulting in the seismically slow, shallow fan delta sediments. The fault is a blind thrust, meaning one side of the fault is being thrust over the other, but the fault does not reach the surface.

This fault therefore appears to have been triggered by the January 2010 event.

The earthquake actually occurred at the boundary of the Caribbean plate and the Gonave microplate, which sits between the North American and Caribbean plates. The flat plain of the Léogâne area experienced some of the worst shaking, destruction of buildings, and loss of life caused by the Haiti earthquake.