Scientists gather, analyze, and evaluate data to solve problems or gain additional information about a topic. Scientists work in many different areas of the world and study a wide variety of topics. Did you know that you can help scientists with their work? Individuals who help scientists collect data are called citizen scientists. Citizen scientists are valuable because citizen scientists enable scientists to gather more data and cover more areas than the scientists would be able to do by themselves.

Citizen scientists often use the Internet to submit data, and citizen science takes a variety of forms. Examples of some citizen science projects include gathering data about soil, asteroids, weather, plants, migratory dragonflies, and earthquakes. Citizen scientists usually have some degree of training in gathering data. Sometimes, however, citizens help with gathering scientific data but have not received training. When this happens, the work they do is referred to as citizen-based science.

The scientists in this study were particularly interested in earthquakes and the data provided by citizen-based science related to earthquakes.

An earthquake happens when two blocks of earth move past each other suddenly (figure 1). The movement of the two blocks of earth causes a release of energy which in turn creates vibrations and movement in the surrounding area.

The place at which the two blocks of earth move past each other is called the fault or fault line. Earthquakes typically start deep within Earth. The point on Earth’s surface above where the earthquake starts is called the epicenter (figure 2).

The U.S. Geological Survey is the Federal Government agency that monitors and studies earthquakes. Earthquakes are recorded by instruments called seismographs (figure 3).

The first seismographs were used in 1890. Since that time, a seismographic network has been built across the United States called the Advanced National Seismic System (figure 4).

Additionally, a larger, global network called the Global Seismographic Network has locations across the planet (figure 5). These two networks of seismographs collect data about the occurrence of earthquakes.

Information from the seismographs help scientists assign a magnitude to an earthquake. Magnitude measures the energy released at the source of an earthquake. Another earthquake measurement is called intensity. Intensity is a measurement of the strength of shaking at a certain location; and an earthquake produces many intensities of shaking at different locations. The Modified Mercalli Intensity Scale is used to measure intensity (figures 6a and 6b). The following table gives intensities that are typically
observed at locations near the epicenter of earthquakes of different magnitudes.

When an earthquake occurs, scientists want to gather as much data as possible. These data enable scientists and decisionmakers to more successfully respond to and prepare for earthquakes.

The Advanced National Seismic System is a nationwide network of seismographs. These seismographs gather and record data about a wide variety of earthquakes across the Nation. However, some earthquakes in remote areas are not recorded due to the lack of seismographs in the area. Some scientists wanted to get a more complete description of earthquakes, including their effects and the extent of damage. The scientists thought that information provided by citizens experiencing earthquakes would be useful. To capture this information, the “Did You Feel It?” (DYFI) system was created in 1997.

The DYFI system allows Internet users to report earthquake data when they feel an earthquake. The data submitted are put into computer programs that create “Did You Feel It?” Maps. The data collected are used to create color-coded maps based on the ZIP Codes. The map colors correspond to the earthquake intensity reported by the DYFI users (figure 7). More than 4 million entries have been submitted from 1999 to 2017.

The scientists wanted to know how the DYFI system changed from 1999 to 2013. The scientists wanted to know the advantages and disadvantages of gathering earthquake intensity data through a citizen-based science network. Additionally, the scientists wanted to measure the accuracy and timeliness of the DYFI system data.

The scientists examined more than 10 years of data from the DYFI system. The scientists compared these data to other earthquake maps and data gathered by the U.S. Geological Survey. National Seismic Hazard Maps are produced every 6 years and display potential earthquake ground motions based on differing levels of probability. These maps help people understand the probability that earthquake ground motion will occur in certain areas. Earthquake ground motion is how much the Earth shakes in response to the earthquake’s seismic waves.

The ground motion probabilities are indicated by different colors on the map. For example, colors on the 2008 map show the levels of horizontal shaking. Horizontal shaking is the ground movement that goes in a horizontal motion. The map shows the chance that in a 50-year period this horizontal shaking will occur (figure 8).

The scientists compared the 2008 National Seismic Hazard Map to a national map based on 10 years of DYFI data (figure 9). Intensity levels are color coded to approximately match each other.

The DYFI national map is based on 1.6 million individual entries from more than 25,000 ZIP Codes. The scientists also compared the DYFI data with ShakeMaps (figure 10). ShakeMaps are maps that represent the ground shaking produced by an earthquake as recorded on the seismic instruments. An earthquake produces a wide variety of ground shaking depending upon the ground’s distance from the earthquake’s epicenter, the rock and soil conditions, and differences in the seismic waves moving through Earth’s crust.

The scientists also compared the data from 10 years of DYFI entries to measure the accuracy and timeliness of the data. The scientists used computers and computer software to analyze the data.

Before the DYFI system, collecting shaking intensity information from citizens in an area impacted by an earthquake required a great deal of effort and time. The data weren’t available until long after the earthquake occurred, and the amount of data was relatively small and sparse. Because of the immense effort required to collect shaking data, intensity maps using the Modified Mercalli Intensity Scale were rarely made for earthquakes with a magnitude of less than 5.5.

DYFI has changed all that! Since DYFI makes collecting the data fast and easy, the scientists found that they can collect information for earthquakes with any magnitude, as long as it was felt. Previously, in areas where there were no seismic instruments close by, some small-magnitude earthquakes were not recorded at all. The scientists found that, based on the data provided through DYFI, even earthquake events with less than a magnitude 2.0 are routinely reported. They also found that the DYFI data are timely. The scientists calculated that, after an earthquake, approximately 62,000 responses are processed in an hour, or around 1,000 responses per minute!

DYFI maps are created not only for earthquakes, but also for other events that cause shaking and vibrations. These other events include mining events and other explosions, supersonic aircraft flights, and bolides.

Additionally, the DYFI data accuracy is high. The scientists found that the large amount of data that is collected through DYFI provides more accurate information overall. The large amount of data could be compared and averaged, and any responses that seemed out of the ordinary could be discarded.

The quality and quantity of DYFI data, however, ultimately depends on how many people experience an earthquake and how many have access to the Internet. Areas with large populations and easy access to the Internet provide better quality and greater quantities of data. The scientists also found that DYFI data from citizen scientist reports usually agree with the ShakeMap data recorded by seismic instruments.

With the DYFI system, U.S. Geological Survey scientists said that they can now monitor and collect data on all felt and reported earthquakes. The DYFI system also provides other benefits. The scientists found that the DYFI system helps educate the public. The system provides a human perspective on an earthquake and creates data that scientists can use to help understand earthquakes better.

The DYFI system also provides emotional support to people experiencing an earthquake. The system gives citizens the opportunity to share and confirm their experiences with each other. The DYFI system provides high-quality and timely data about earthquakes. This information allows scientists to better understand and respond to earthquake events.

Additionally, the scientists found limitations to the DYFI system. They found that the highest rates of response came from areas with large populations, easy Internet access, and a lack of significant damage and power outages. Therefore, the DYFI system may lack entries from areas harder hit by earthquakes.

These missing data would be important for better understanding an earthquake. However, the main purpose of the DYFI system is to provide scientists with more data to evaluate earthquakes after they have occurred. The DYFI system has provided scientists and the public with more data about earthquakes. Moreover, these data are provided in a timely manner.