RESTON, Va. - The threat of additional damaging earthquakes in Haiti will remain for the next year.

The U.S. Geological Survey (USGS) issued an update to its Jan. 21, 2010, statement, which includes the aftershock probabilities for the next 30-to-90-day period and for the overall year.

U.S. Geological Survey Director Marcia McNutt asked the team of USGS earthquake scientists to continue to provide an evaluation of the earthquakes facing Haiti now and in the future. Here is the updated statement in its entirety from the USGS:

This statement revises and updates the statement issued by the USGS on Jan. 21, 2010.

The magnitude-7 earthquake of Jan. 12, 2010, near Port-au-Prince, Haiti, has generated a sharp increase in concerns about the potential for future earthquakes in Haiti and the surrounding region. These concerns extend to understanding the causes of the earthquake hazard and learning what can be done to ensure seismic safety in the future. The purpose of this statement is to convey our best judgment on these subjects.

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Source: USGS

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Tsunamis send electric signals through the ocean that appear to be sensed by the vast network of communication cables on the seabed, according to a new study led by Manoj Nair of the University of Colorado and NOAA.

Nair and his colleagues used computer models to estimate the size of an electric field created by the force of the 2004 Indian Ocean tsunami as it traveled over major submarine cables. Salty seawater, a good conductor of electricity, generates an electric field as it moves through Earth's geomagnetic field.

"We estimate that the 2004 tsunami induced voltages of about 500 millivolts (mV) in the cables. This is very small compared to a 9-volt battery, but still large enough to be distinguished from background noise on a magnetically quiet day," Nair said. "By monitoring voltages across this network of ocean cables, we may be able to enhance the current tsunami warning system."

But Nair cautioned that much research is still needed to effectively isolate the tsunami signals from other sources, such as Earth's upper atmosphere, or ionosphere, whose signals can reach 100 mV. One millivolt is equivalent to one-thousandth of a volt.

Tsunamis are created by a large displacement of water resulting from earthquakes, landslides, volcanic eruptions, and even meteors hitting the ocean. Vessels far out at sea may not notice the waves passing underneath at the speed of a jetliner, because the wave heights are very small in the deep ocean. This makes their detection and monitoring a challenge.

The current tsunami warning system relies on a global seismometer network to detect earthquakes that may indicate that a tsunami has formed. Deep-ocean pressure sensors and coastal tide gauges are the only tools available to detect and measure an actual tsunami. The electric current induced in submarine cables may provide an additional way to confirm and track a tsunami.

Since the 2004 tsunami, the international warning system has expanded to include 47 deep-ocean pressure sensors, most of them in the Pacific area. After an investment of more than $100 million and strong support of Congress, NOAA has made tsunami warnings and education a priority. Within the United States, real-time data from these deep ocean sensors are used to forecast the impact of the tsunami on U.S. shorelines.

Co-authors are Alexei Kuvshinov of the Swiss Federal Institute of Technology, Zürich, S. Neetu of the National Institute of Oceanography, India and T. Harinarayana of the National Geophysical Research Institute, Hyderabad, India. Nair is also associated with NOAA's Cooperative Institute for Research in Environmental Science at the University of Colorado.

The study will appear in the February edition of the journal Earth, Planets and Space.

Source: NOAA

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NOAA's National Hurricane Center in Miami will issue watches and warnings for tropical storms and hurricanes along threatened coastal areas 12 hours earlier than in previous years. According to NHC experts, advancements in track forecasts are making it possible for forecasters to provide greater lead time.

Tropical storm watches will be issued when tropical storm conditions are possible along the coast within 48 hours. Tropical storm warnings will be issued when those conditions are expected within 36 hours. This is an increase of 12 hours from those issued in previous years.

Similar increases in lead-time will apply to hurricane watches and warnings. The hurricane watches and warnings will generally be timed to provide 48 and 36 hours notice, respectively, before the onset of tropical storm force winds. That additional time will also allow people preparing for the storm - securing oil rig platforms, getting food and water stockpiled, boarding windows, etc., - enough time to finish preparations and get to safe shelter.

"With increases in population and infrastructure along vulnerable U.S. coastlines, emergency managers need more lead time in order to make life-saving decisions regarding evacuations," said Bill Read, director of NOAA's National Hurricane Center.

These changes will go into effect for the 2010 hurricane season, which begins on May 15 in the Eastern Pacific and on June 1 for the Atlantic Basin.

Source: NOAA

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