PAGER - Rapid Assessment of an Earthquake's Impact

RESPONDING TO GLOBAL EARTHQUAKE HAZARDS

PAGER (Prompt Assessment of Global Earthquakes for Response) is an automated system to rapidly assess the number of people and regions exposed to severe shaking by an earthquake, and inform emergency responders, government agencies, and the media to the scope of the potential disaster. PAGER monitors the U.S. Geological Survey’s near real-time U.S. and global earthquake detections and automatically identifies events that are of societal importance, well in advance of ground-truth or news accounts.

The U.S. Geological Survey’s National Earthquake Information Center (NEIC), located in Golden, Colorado, reports over 30,000 earthquakes a year. Tragically about 25 of these cause significant damage, injuries, or fatalities. The U.S. Geological Survey (USGS) often detects earthquakes well before eyewitness reports are available. It must then decide rapidly whether Federal and international agencies should be alerted to a potentially damaging event. In the past, the USGS primarily relied on the experience and intuition of its on-duty seismologists to estimate the impact of an event. To improve the accuracy of the assessment, the USGS has developed PAGER, an automated system to rapidly estimate the number of people and settlements exposed to severe shaking during earthquakes occurring anywhere in the world.

PAGER provides important information to help emergency relief organizations, government agencies, and the media plan their responses to earthquake disasters. Content includes instrumentally-determined earthquake parameters of location, magnitude, and depth and an estimate of the number of people exposed to different severities of shaking—a useful indicator of potential impact. For most events, the system generates a comment describing infrastructure vulnerability in the region, and damage and fatality reports from previous nearby earthquakes. A table summarizes the predicted shaking intensity at nearby population centers, and maps provide quick visual overviews of shaking levels and population densities.

This information is available on the USGS earthquake website http://earthquake.usgs.gov/ and as a printable, one-page report with accompanying description such as that shown in the following pages. Fundamental to such a system, the USGS operates a robust computational and communication infrastructure necessary for earthquake response.

PAGER results are generally available within 30 minutes of a significant earthquake, shortly after the determination of its location and magnitude. However, information on the extent of shaking will be uncertain in the minutes and hours following an earthquake and typically improves as additional sensor data and reported intensities are acquired and incorporated into models of the earthquake’s source. Users of PAGER exposure estimates should account for uncertainty and always seek the most current PAGER release for any earthquake.

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http://earthquake.usgs.gov/pager/

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F The PAGER Process

At the heart of PAGER are the timely and accurate earthquake location and magnitude determinations that the USGS has been producing for decades. PAGER uses these earthquake param-

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eters to calculate estimates of ground shaking by using the methodology and software developed for ShakeMap (http://earthquake.usgs.gov/shakemap/).The ShakeMap system produces maps of regional ground shaking using a sitespecific ground-motion amplification map, seismic wave attenuation equations, and reported or recorded intensities. The number of people exposed to various levels of shaking is then calculated by combining

Ground Shaking

the maps of predicted ground shaking with Oak Ridge National Laboratory’s Landscan population database. Finally, PAGER generates a regionally specific description of the vulnerability of the exposed population and infrastructure, potential for earthquakeinduced landslides, and, if available, damage and fatality reports from previous nearby historic earthquakes for comparison purposes and damage projection.

Using the estimates of population

Population

exposure, PAGER determines the scope of the catastrophe and issues alarms to emergency responders, government agencies, and the media. PAGER is an iterative and interactive system. As subsequent information becomes available, more accurate maps of ground shaking are produced, refined estimates of population exposures are made, and updated alarms are issued, if necessary.

Ongoing PAGER Developments

At present, PAGER notifications and Web pages provide estimates of the population exposed to each seismic intensity level, a useful indicator of potential impact. USGS is improving the system to include a more comprehensive alert that will include casualty estimates, motivated by the idea that an estimated range of possible number of deaths will aid in decisions about humanitarian response.

The ability to model casualties and economic loss is being developed through several models that use approaches ranging from largely empirical to largely analytical. Selection of the most appropriate model for a particular earthquake will depend on how much is known about local building inventory and their vulnerability.

To calibrate the loss models, the USGS has generated an atlas of 3,900 ShakeMaps of significant global earthquakes that have occurred during the last 36 years. The calibration of loss methodologies relies on this atlas and on fatality and damage data collected by the NEIC. Related USGS developments under

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the auspices of the PAGER Project include rapid determination of fault geometry, size and rupture characteristics, global estimates of seismic soil-amplification patterns, ShakeMap enhancements, ground-motion and loss-uncertainty analyses, and intuitive ways to portray casualty and loss information and their uncertainties.

Acknowledgments

PAGER development and maintenance is supported by the U.S. Geological Survey under the Advanced National Seismic System (ANSS) and a grant from the U.S. Agency for International Development/Office of Foreign Disaster Assistance (USAID/OFDA).

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