Learning from Sumatra
The Dec. 26, 2004, Sumatra event was the largest earthquake in 40 years. It was also the first magnitude-9 giant to be captured by global networks of modern seismic instruments. The observations, capable of recording a broad spectrum of the energy released, provided a much more complete picture of this earthquake than was possible in 1964 when the Great Alaska earthquake struck. Geodetic data from Global Positioning System stations, also unavailable in 1964, provided crucial constraints on the extent of the Sumatra rupture. Researchers are working to improve their ability to rapidly determine when a giant earthquake is under way. Such improvements would be a major benefit for tsunami warnings.
After the Dec. 26 event, tsunami experts were quickly deployed to Indonesia, Thailand, India, Sri Lanka and Malaysia to measure run-up heights and deposits left behind by the giant waves. Such measurements allowed them to make comparisons to deposits from previously studied events and those found in the geologic record. One such team was heading for the west coast of Sumatra when the regions second largest earthquake in 40 years occurred on March 28, a magnitude-8.7 rupture farther south along the same subduction zone. The team, led by Bruce Jaffe of the U.S. Geological Survey (USGS), Gegar Prasetya of the Indonesian Tsunami Research Center and Jose Borrero of the University of Southern California, was able to quickly take measurements from the much smaller local tsunami generated by the second quake. Observations from the two events are helping researchers to better understand the factors controlling the generation of large tsunamis.
|The Sumatra earthquake raised awareness that infrequent events are indeed real and can be devastating.|
Upgrading global tsunami warning capabilities has been a major priority in
the past year. The U.S. Agency for International Development has provided funds
to cooperatively develop a tsunami warning system for the Indian Ocean with
the countries in the region and a number of other nations that have offered
their assistance, such as Germany and Japan.
In January, President Bush announced an initiative to improve the present warning system in the Pacific Ocean and add warning capability in the Atlantic Ocean and Caribbean Sea. The presidents initiative, which was funded through supplemental appropriations in May, has also made it possible for USGS to make nearly all Global Seismographic Network stations available in real time, as well as adding seismic stations in the tsunami-prone Caribbean, and to modernize the computational infrastructure at the National Earthquake Information Center in Golden, Colo., which will institute 24/7 operations at the end of the year. Together, these improvements will greatly speed up the issuance of global earthquake alerts.
Making hazards real
For many people in the United States, the Sumatra earthquake raised awareness that infrequent events are indeed real and can be devastating, sparking renewed interest in the potential for repeats of the 1700 magnitude-9 earthquake along the Cascadia subduction zone and the 1811-1812 New Madrid earthquakes. Effectively seizing such a teachable moment takes more than providing the annual probability of ground shaking for a given metropolitan area. Scientists must also convey the toll such shaking will take on people, property and infrastructure. Such an approach requires geoscientists to partner with a wide range of engineers, planners, emergency managers, social scientists, businesspeople and others.
Several scenarios were released in 2005, including two for the Pacific Northwest: The Cascadia Regional Earthquake Working Group published a scenario for a magnitude-9 event on the Cascadia subduction zone (www.crew.org), and the Earthquake Engineering Research Institute and Washington State Emergency Management Division published a scenario of a magnitude-6.7 earthquake on the Seattle Fault (www.eeri.org). The latter is particularly comprehensive in its estimates of the long-term disruption and impacts to buildings, lifelines and other public infrastructure, with projections of more than 1,600 deaths, one-quarter of commercial buildings in Seattle significantly damaged, and total costs on the order of $33 billion.
As we head into the new year, a centennial scenario is worth keeping in mind: that of the 1906 earthquake that left 3,000 dead in San Francisco and more than half the citys population homeless. Today, a consortium of scientists, engineers and planners are preparing scenarios for a modern repeat of the 1906 quake. Were a repeat of that magnitude-7.9 event to occur today, the likely impacts include thousands of casualties, bridge failures, school collapses, disrupted water supplies, fires due to ruptured gas pipelines, and building-related losses alone topping $60 billion. This scenario and a plethora of other information will be released around the centennial anniversary next April.
Katrina and recovery
Although the Sumatra earthquake and tsunami began the process of making catastrophes real to people in this country, they still happened somewhere else. That was not the case with Hurricane Katrina, which along with Hurricane Rita delivered a one-two punch to the Gulf Coast. Geoscientists have already contributed a great deal in support of the response to these events, and they have a great deal more to contribute to the decision-making for long-term recovery. It remains to be seen whether science will influence recovery decisions amidst the cacophony of interests that have converged on New Orleans and the rest of that region.
For science to play a role in the recovery requires our society to learn this essential lesson: Even for a city below sea level, catastrophe was not inevitable. Actions that were within fiscal reach could have been taken that would have reduced the impact of such a storm, and actions can be taken in advance of the next big one be it hurricane, earthquake or other extreme event to build resilience and reduce vulnerability. Ten years from now, it would be awfully nice to review the catastrophes that did not occur rather than simply the ones that did.