Fri May 18, 2012
Reporter, Marisa Lubeck
Breaking Ground
By Marisa Lubeck, Colorado – May 2010
The year’s torrent of deadly and devastating earthquakes has dominated headlines and, for many people, incited an uncomfortable question: Is the world was on the verge of ending? Scientists say no. In fact, these earthquake occurrences are statistically normal, according to the U.S. Geological Survey (USGS)
Since January, six major quakes were recorded at greater than 7.0 magnitudes, including the January 12 quake that devastated Haiti and the massive 8.8 magnitude Chilean earthquake that occurred on February 27. Aside from the infrastructure damage these quakes caused—particularly the Haitian event that demolished over 97,000 homes in the Port-au-Prince region—the earthquakes that struck Haiti, Chile, Indonesia, Baja California, and the Qinghai Province of China killed over 223,000 people (the majority as a result of the Haitian quake). Thousands more were injured, and about 1.3 million people were displaced in Haiti alone.
“Statistically, there is no evidence that earthquakes have become more frequent lately than they ever have been,” said Gavin Hayes, a USGS geophysicist at the U.S. Geological Survey in Golden, Colorado. “Random processes such as earthquakes, by nature, sometimes produce large events very close together in time.”
Hayes works at the USGS National Earthquake Information Center (NEIC) in Golden, Colo., the only governmentally-mandated organization to locate earthquakes worldwide and distribute earthquake data to interested parties such as governments, aid agencies, media and the public.
By examining energy release from earthquakes through time, the USGS NEIC has determined an approximate constant rate: About 17 magnitude 7.0 or greater earthquakes occur in an average year, and six earthquakes of this size have occurred as of mid-April, 2010. Seismically, it has been a normal year thus far.
“The most likely cause for the dominance of earthquakes in the news is increased speed and awareness of the global media and public—more information is distributed quicker—and population increases in cities that are at high risk of earthquake damage,” Hayes said.
All regions close to major plate boundaries are at risk of large earthquakes, as are many away from such boundaries. While it is difficult to pinpoint specific locations, most areas around the Pacific Rim (the “Pacific Ring of Fire”), and other areas such as Sumatra/Indonesia, the Himalayan front in northern India, Iran and Pakistan, Turkey, and the Mediterranean are at high risk.
Areas in the United States are also at risk. In California, there is a 46 percent chance that a magnitude 7.5 or greater earthquake will occur in the next 30 years, most likely in the southern half of the state, according to a 2008 USGS study.
Earthquake vulnerability is related to the typical building practices of a country. Anywhere with large populations and poorly-built or unreinforced structures that are close to large faults are at high risk from damage, and many such cities are concentrated in the developing world. In the United States, areas of high seismic hazard such as California have strict and strictly enforced building codes that would mitigate the damage from the next large earthquake in that region, according to Hayes.
“What you experience during an earthquake depends on several factors,” Hayes said. “Primarily, how far you are from the earthquake (shaking becomes less intense with distance), how big the earthquake was (you will feel more shaking from large earthquakes), and the local geology and soil conditions under your feet (soft, thick soil will amplify ground motions).”
According to the USGS, a large earthquake like the recent 8.8-magnitude Chilean event will be apparent to people in the vicinity as a sudden, violent jolt followed quickly by strong shaking that may last up to a couple of minutes, making it difficult to stand up. Those farther away may experience a strong earthquake as a gentle bump followed several seconds later by more intense, rolling shakes that pass quickly. A small earthquake nearby will feel like a small sharp jolt followed by a few stronger shakes, passing quickly.
Does a phenomenon that literally shakes the earth at least provide a warning? Can earthquakes be predicted?
“Unfortunately, no,” Hayes said. “The most promising areas of research in a related field are for ‘earthquake early warning’—detecting an earthquake very soon after its occurrence, and giving nearby populations a seconds to minute lead-time that strong shaking is about to occur. This hopefully gives enough time for people to move to safer locations, to shut down trains, gas lines, and the like, in order to mitigate the damage earthquakes cause.”
When science can’t predict, technology can often respond, and the USGS NEIC has developed a number of tools to improve earthquake response. On the fifth floor or the NEIC building, an array of computer screens digitally showcases colorful seismometers. These instruments measure ground motion at several hundred seismic stations across the globe, and display the seismic waves as what looks like a complex rainbow of squiggles running horizontally across the monitors. They are a chaotic-looking exhibit of seismic information, in contrast to the tranquility of the Rocky Mountain foothills visible through large windows on the opposite end of the room.
Analysts who work alongside Hayes collect and redistribute this data 24/7 at the USGS NEIC. They work in shifts, responding immediately to earthquakes wherever they take place around the world and releasing information related to their location, size, and exposure as quickly as possible.
“Essentially, we’re the go-to guys for earthquake information, and through us, earthquake analyses can proceed in a rapid, systematic manner,” Hayes said.
The USGS Prompt Assessment of Global Earthquakes for Response (PAGER) system estimates the number of people and the cities worldwide that may have been subjected to severe shaking following a large earthquake. New developments to the system will incorporate alert levels such as yellow, orange, and red related to the need for local, national, or international response efforts, which are based on estimates of fatalities and economic losses from the earthquake in question.
“This dual system recognizes that fatalities tend to drive major response for large global earthquakes in under-developed nations, whereas economic loss drives response domestically and in other parts of the developed world,” Hayes explained.
The color-coded system associated with these alerts also conveys the probabilities of lower or higher alert levels, and thus quickly and accurately portrays the likely societal impacts from earthquakes. These estimates are based on a vast database of historic earthquakes, their shaking distributions, and impacts, compiled and collected at the USGS over the past several years.
The USGS Twitter Earthquake Detector, or TED, databases public tweets containing the word “earthquake” and its equivalent in other languages, and applies place, time, and key word filtering to gather geo-located first-hand accounts of shaking. TED is currently being tested internally at the USGS; in the future, the hope is to use this application to distribute earthquake alerts through the Twitter application, Hayes said.
Other USGS social response techniques include:
ENS (Earthquake Notification System) – A user-subscribed system through which people can receive text messages and/or emails regarding recent earthquakes. Each user is given an individual profile, so one can customize alerts based on earthquake size thresholds, and/or locations of interest.
Did You Feel It? – A questionnaire system that can be filled out after an earthquake by members of the public who have felt the event. The questions and their answers are geared towards determining the level of shaking experienced by the user. Given a users’ approximate location (e.g. zip code), such observations thus gives us important information related to the distribution of shaking of an earthquake.
ShakeMap – Uses local strong motion data recording an earthquake, Did You Feel It? responses, and/or empirical relationships that relate the location and size of an earthquake to its ground shaking, to estimate the distribution of perceived ground shaking after an earthquake, according to the Modified Mercalli Intensity Scale.
Science generated by facilities like the USGS NEIC can help decipher facts amidst fear and potentially mitigate those dangers that do exist.
“Earthquake science is extremely important for characterizing and understanding the hazards that result from these natural phenomena,” Hayes said. “Without our science, we wouldn’t know why earthquakes occur where they do, how often they can reoccur, and what we can do to protect ourselves from their effects. Without earthquake science, buildings would probably be just as likely to fall down after an earthquake today as they ever were, or more so because building designs have changed and have become increasingly elaborate. As populations expand at the same time, it is critical to explore how we can make those populations as safe as possible given the unavoidable hazards that earthquakes pose.”
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