Dr. P. Patrick Leahy
Associate Director for Geology
U.S. Geological Survey
The El Salvador Earthquake, and Lessons for the United States
First, let me recognize your leadership and foresight as co-sponsors of this Natural Hazards Caucus. We appreciate your interest in these issues, which are vital to the health and well-being of our citizens and our society.
Update on El Salvador earthquake and landslides
A major earthquake occurred off the coast of El Salvador about 65 miles (110 km) SSE of San Salvador, and 60 miles SW of San Miguel, at 12:33 p.m. EST, Jan. 13, 2001 (11:33 a.m. local time in El Salvador). A preliminary magnitude of 7.6 was computed for this earthquake. [National Earthquake Information Center map of event]
According to preliminary reports, at least 600 people were killed, 2400 were injured, and 440 are missing. More than 45,000 houses were destroyed in El Salvador. Most of the damage and casualties were caused by a large landslide at Santa Tecla. The earthquake was felt as far north as Mexico City and in tall buildings in some cities of Colombia. At least 6 people were killed in southeastern Guatemala.
Several USGS scientists were already in Central America working on the recovery from Hurricane Mitch; they conducted reconnaissance studies of earthquake effects and landslides Wednesday in San Salvador and the surrounding towns, as well as visiting Santa Ana volcano about 60 km WNW of San Salvador to follow up on reports of possible eruptive activity. The U.S. military provided air support (a Blackhawk helicopter), allowing the team to cover extensive areas in and around the city; we greatly appreciate their support.
The primary earthquake effect was structural damage to unreinforced masonry residential and business structures. Large buildings and most well-engineered structures appear to be only lightly damaged. Most buildings had no broken windows, and collapsed buildings were found primarily in the poorly built parts of the city. This pattern of damage shows the value of building codes that protect against seismic damage.
Earthquake-induced landslides were scattered throughout the region. The landslides were particularly big and numerous in areas of volcanic ash deposits. [Image of Las Colinas landslide] Landslides have blocked several roads, including the Pan American Highway. The team has heard apparently reliable but unconfirmed reports of landslide dams on streams and rivers.
There was an initial report that a new small lava dome was building in Santa Ana caldera, but a tiltmeter and aerial observation of the volcano crater showed no evidence of any magma buildup. Jim Vallance and Ed Harp (two members of the USGS team) met with the President of El Salvador to discuss their initial observations. Our counterpart agency in El Salvador is installing a portable seismometer on the flank of the volcano.
The USGS will be intensifying cooperative investigative efforts as requested and as the situation warrants.
Why does an earthquake in El Salvador matter to the United States?
There are clear humanitarian reasons for providing assistance when another country is ravaged by natural disaster. In addition, disasters in other lands often have costs that are borne by the United States, including the expense of military deployment, and economic effects resulting from the increasing globalization of the world economy. The value of foreign work is not just humanitarian or even economic, however; there are very pragmatic benefits as well. Studying the causes and effects of natural disasters provides the United States with much more information about how these extreme natural events happen, so we can apply the knowledge to safeguard our citizens.
Two recent earthquakes--El Salvador and the 1999 Taiwan earthquake-- both triggered major landslides. We need to learn more about why such landslides occurred in certain places, so that we can be better prepared when a similar disaster hits Alaska, California, or the Pacific Northwest... all of which are seismic areas with a history of landslides. There are also some similarities between the geologic setting of El Salvador and that of the Pacific Northwest, where we know of historic damaging earthquakes (for example, a magnitude 6.9 event in 1949 and a magnitude 6.5 event in 1965 caused significant damage in the Seattle area). Studying earthquake processes in El Salvador can help residents of both San Salvador and Seattle better prepare for the next big earthquake.
The largest recorded earthquake in the United States was the Good Friday earthquake in Anchorage in 1964; this event also occurred along this active plate boundary, known as the Pacific Rim of Fire. In the past 25 months, four earthquakes of magnitude 6.5 or larger have hit Kodiak, not far from Anchorage.
There are similarities between the geologic situation in El Salvador and the setting of the Cascades volcanoes, especially Mt. Rainier, and to some extent the volcanoes of the Aleutian arc. These volcanoes are found along active tectonic boundaries, where earthquakes and volcanoes signal the presence of the moving plates. The risk from volcanic mudslides at Mt. Rainier is acute; at the foot of the volcano is a growing urban/suburban area, with towns built right on top of old mudflows. The USGS is working closely with local community leaders, FEMA’s Project Impact, the National Park Service, and other stakeholders to be sure the risks are known and the communities are prepared.
Broader lessons for the United States
Recent major natural disasters--Hurricane Mitch, the Venezuela landslides, the Turkey and Taiwan earthquakes, and now El Salvador--remind us that we live on an active planet. Our vulnerability is a function of where we choose to live and build.
There are two crucial aspects to living safely on our land: knowing the hazards, in order to stay out of harm’s way, and improving our monitoring and warning systems, in order to get out of harm’s way when the hazard approaches.
The El Salvador earthquake occurred at a plate boundary, where the Cocos plate is being pushed under the Caribbean plate. But not all earthquakes occur at plate boundaries. [Note: On January 26, a few days after these remarks, a major intraplate earthquake in Gujarat, India, caused thousands of deaths and tens of thousands of injuries.] The largest earthquake in the history of the conterminous United States struck New Madrid, Mo., in 1811; 75 years later, Charleston, S.C., was rocked by a major earthquake that was felt in Chicago, Boston, and other cities more than 800 miles away. To safeguard the public, to provide the information people need so they can be safe, requires knowing local conditions as well as the broad geologic framework. We must understand the risks we face and prepare for them to ensure the long-term health and well-being of our society. [Global Seismic Hazards map] This is a challenging task.
Advances in science and technology are enabling a better understanding of earthquake risks and earthquake shaking. The Advanced National Seismic System is a plan for a national network of about 7,000 earthquake monitoring instruments. ANSS has received small increments of funding for FY 2000 and 2001. In its first year, 80 seismometers were installed in San Francisco, Seattle, and Salt Lake City; we plan in this fiscal year to install more instruments in these three urban areas as well as new instruments in Anchorage, Reno, and Memphis. We work closely with our partners and customers on these projects--at Anchorage, for example, we are working with the Alaskan Volcano Observatory, the University of Alaska-Fairbanks, and NOAA’s Tsunami Warning Center in Palmer, as well as with state and local geologists and elected officials, emergency response managers, and engineers. The new monitors will allow maps of the most intense shaking to be posted on the web in 4-10 minutes after an earthquake, so emergency responders will know where to send their equipment. In addition, the monitors will provide better information to engineers and scientists, for developing better building codes and improving our understanding of the Earth.
Earthquakes throughout the Pacific region can generate tsunamis that endanger the United States--for example, the 1960 Chile earthquake triggered a tsunami that killed 61 people in Hawaii. The great Anchorage earthquake in 1964 generated tsunami waves of more than 20 feet at Crescent City, California, and killed 11 people there, in addition to more than 100 killed in Alaska.
USGS is the only group in the United States that is federally funded to monitor and report on seismic activity, gathering the essential basic information on the occurrence of earthquakes for scientists and planners across the United States and the world.
This work is important to all of us, not just to California and other earthquake-prone areas, because we all pay for natural hazards, no matter where they occur. The 1999 Taiwan earthquake affected Hewlett Packard’s profits for the quarter, because it disrupted the supply of computer chips that HP acquires from manufacturers in Taiwan. The cost of natural disasters in the United States has averaged $25-50 billion a year over the past decade, and costs continue to rise.
The Federal government has an essential role in providing basic scientific and monitoring information for the Nation. USGS is proud to play its part. Because of past investments in science and engineering to ensure life safety, most of the U.S. disaster losses are economic; the death toll from natural disasters has dropped significantly over the past century. Compare the effects of Hurricane Mitch in Central America in 1998 with those of Hurricane Floyd in the United States-- there was much less loss of life from Floyd, although the disruption was still severe. The primary impact of Hurricane Floyd has been economic.
The United States has been relatively lucky in recent years, but there are no guarantees. If a major hurricane hit New Orleans, it could cause thousands of deaths. The 1994 Northridge earthquake took place at 4:30 a.m. and caused a number of highway collapses. Had it happened in rush hour, there would probably have been many more deaths. There’s no reason to think our luck will last forever. Let me reiterate: The way to protect our communities begins with understanding the local conditions and risks, and that requires having the right equipment to know what’s going on.
Monitoring streamflow provides another example. The USGS works closely with the National Weather Service to provide the information about river levels that they need to make flood forecasts. A national plan for streamgages was developed in 1998 in response to a Congressional request, and increased funding for FY 2000 and 2001 has allowed us to build or reactivate a total of 100 gages needed for flood forecasting and upgrade more than 180 other stations in various ways. We are also working to ensure the accessibility of the data over the World Wide Web, so people can know what to expect and can get out of harm’s way if--or when--it becomes necessary.
Although I’ve focused on the USGS role in this presentation, it is clear that we cannot do it alone. Because the problem of natural hazards is so complex, solutions need to involve many perspectives, many partners. I’ve mentioned some of our partners already. FEMA and the National Weather Service are two of the most significant with respect to our hazards work, but there are many, many more, including partners at the State and local level, in universities, in private-sector organizations like those here who are providing such strong support to the caucus through its working group.
Much work remains to be done. We look forward to continuing advances in national awareness of these issues, under your leadership.
Posted January 31, 2001