The Next Great Earthquake

The 2004 Sumatra-Andaman earthquake and resulting tsunami are now infamous for the damage they caused, but at the time many scientists believed this area was unlikely tocreate a quake of such magnitude.

In the March 23 issue of the journal Science, a geophysicist from Rensselaer Polytechnic Institute urges the public and policy makers to consider all subduction-type tectonic boundaries to be "locked, loaded, and dangerous."

"Seismologists have long tried to determine which subduction boundaries are more likely than others to break," says Robert McCaffrey, professor ofearth and environmental sciences at Rensselaer. "Yet, the great earthquake of 2004 ruptured a segment that was thought to be among the least likely to go."

On Dec. 26, 2004, the earth beneath the Indian Ocean buckled and ruptured, unleashing one of the largest earthquakes in recorded history. Shockwaves from the magnitude 9.2 (M9) quake created a wall of rushing water that devastated communities up to 1,000 miles away.

M9 earthquakes typically occur at a specific type of tectonic boundary called a subduction zone, where one plate is gently slipping underneath another plate, which causes friction, cracking, and lifting of the plates. An M9 earthquake can be created by only 20 meters of slip between two converging plates -- less then the length of an 18-wheeler truck -- but its effects can be global in their impact.

Slips of this length only occur every 200 to 1,000 years or more at aparticular boundary, leaving no reliable historic records to track their frequency, McCaffrey notes. Complete records are only available going back 100 years. Scientists had widely accepted that the age and speed of the subducting plate is important in creating M9 earthquakes, based primarily on support from this 100-year historical record.

But this narrow understanding put the Sumatran subduction zone in avery low risk category. McCaffrey suggests that such limited records are incapable of mapping a trend in geological events that could be several centuries or more apart.

Geologists also focused on the temperature of subduction zones, indicating that temperature at the plate convergence region plays a strong role in the strength of a resulting earthquake. These thermal considerations place the Andaman subduction zone in the high-magnitude class, but one pitfall with this type of classification is that it characterizes some subduction zones as being incapable of producing an M9.

"[The day of the quake], Earth gave us a stark reminder of the important difference between improbability and impossibility," McCaffrey says. "Our understanding of where and when the next great earthquake will happen is in its infancy at best. We have not had enough time to decipher M9 behavior."

In creating new public policy, McCaffrey urges officials to consider all subduction zones as lethal. "Several are near densely populated landareas, and the potential impacts of shaking and tsunamis cannot be overstated," he says.

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Officials Update Tsunami Recovery Two Years Later

Though the U.S. was among the largest contributors, the global response to the events of December 26, 2004 was essential in meeting the immediate needs of the affected populations of the region and to prevent a secondary disaster due to lack of sanitation and other public health concerns, according to officials who led the effort.

Mark Ward, senior deputy assistant administrator for the U.S. Agency for International Development (USAID), spoke at a tsunami relief and recovery update briefing at theNational Press Club in Washington. The purpose of the event was to provide an update on reconstruction activities in the region in recognition of the second anniversary of the Indian Ocean tsunami. Also speaking was Eric Schwartz, the UN Secretary General's Special Envoy for Tsunami Recovery.

An undersea earthquake in the Indian Ocean occured on Dec. 26, 2004, triggering a series of devastating tsunamis killing more than 275,000 with thousands of others missing, with recent analysis compiled lists a total of 229,866 people lost, including 186,983 dead and 42,883 missing, according to Wikipedia. The catastrophe is one of the deadliest disasters in modern history.

The needed responses were met by the cooperation of the people and governments of the region and by public and private organizations and governmentsaround the world, according to officials who spoke at the Press Club.

In the two years since the tsunami, much work has been done to rebuild lives and livelihoods and U.S. government assistance has totaled more than$840 million in this effort. In addition, U.S. charitable donations haveexceeded $1.8 billion, according to the Center on Philanthropy at Indiana University.

As a result of this generosity, the U.S. is working with the affectedregions to rebuild infrastructure, provide jobs and training (particularly for women), strengthen communities and local governments, and develop early warning systems and effective disaster response programs.

"I'm pleased with our program to date, but more needs to be done," says Ward. "We're building roads that will withstand a tsunami, water sanitation systems, clinics, and homes. We're also providing job training and credit for small businesses. All of this is needed for a self-sufficient recovery."

Ward chaired both the USAID Tsunami Task Force as well as the USAID South Asia Earthquake Task Force and is now leading the U.S. government's Lebanon Reconstruction Task Force.


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