xv. USGS ‘Did you feel it?

Interaction Type public -> government
Trigger Event Paucity of instrumental ground-motion data in regions of low seismicity (Atkinson and Wald, 2007).
Domain Provision of ground-motion data to US Geological Survey Community Internet Intensity Map for public information about earthquake activity
Organisation United States Geological Survey Community Internet Intensity Map (popularly known as “Did you feel it?”, or DYFI).
Actors U.S. Geological Survey Earthquake Hazards Program
Data sets in use Various products are developed by the USGS from the DYFI data and other earthquake sensing and monitoring programs.
Process Citizens, upon feeling earthquake activity, must logon to the DYFI website and submit their observation. The intensity of the earthquake they have just experienced is quantified using the Modified Mercalli Intensity (MMI) scale. There is no need for the citizen to have experience in seismology. Maps and graphics are generated automatically by the DYFI system and made available to the public.
Feedback Their submission is acknowledged and DYFI provides personalized feedback to the contributor in the form of a computed intensity for their submission. Users can provide contact details in the input form.
Goal Outreach to citizens to become part of the seismic monitoring network and to allow the USGS to continue to learn and understand more about earthquake shaking and intensities.
Side effects The data collected from DYFI is made compatible with ShakeMap: ShakeMap is a product of the U.S. Geological Survey Earthquake Hazards Program in conjunction with regional seismic network operators.
Contact Point David Wald, U.S. Geological Survey

The US Geological Survey’s Community Internet Intensity Map (more commonly referred to as ‘Did you feel it?’) is a website that automatically maps reports from citizens about their perception of recent seismic activity in their areas. If a citizen feels a tremor of an earthquake these people can visit the DYFI website, report their location and describe their experience by answering a short series of questions (with drop-down menus). In combination to a large network of sensors which are placed all over the world these additional citizen reports allow USGS to develop a more detailed map of the intensity of an earthquake’s shaking. Over 4 million  earthquake intensities have been submitted to DYFI for thousands of earthquakes; the data and DYFI maps are available to browse online on the archive section of the website. There is an option for citizens to give first-person descriptions of how the earthquake affected them. However, it is made clear on the form that if the USGS use this qualitative information the citizen will only be referred to as “the observer”. Contributors can watch the DYFI webpage for the display of their report. Maps and graphics are generated automatically by the DYFI system and made available to the public.

DId you feel it.jpg

The interactive DYFI Map interface with 1-km geocoded boxes color-coded to the USGS ShakeMap/DYFI intensity scale.

The ‘Did you feel it?’ form interface is easy to use. Citizens reporting earthquake shaking can submit observations by selecting their location automatically, from an address or with the map interface. The form is mostly drop-down list based asking for feedback on: Your situation when the earthquake occurred, your experience of the earthquake (shaking strength, duration, reaction), earthquake effects (e.g., objects move or fall off shelves), and damage to buildings. Because DYFI appeals widely to people, the quality and vast quantity of the data have been used to address longstanding issues in earthquake ground-motion science. Such issues have been difficult to address due to the paucity of instrumental ground-motion data in regions of low seismicity (Atkinson and Wald, 2007; Wald et al., 2011). Prior to this system, intensity maps were rarely made for U.S. earthquakes of magnitude less than about 5.5; now intensities as low as magnitude 2.0. are routinely reported for the smallest felt earthquakes nationwide (Atkinson and Wald, 2007; Wald et al., 2011). Upon feeling earthquake activity, must logon to the DYFI website and submit their observation. The intensity of the earthquake they have just felt is quantified using the Modified Mercalli Intensity (MMI) scale. MMI measures the intensity of ground motions from the perspective of human and structural response on a qualitative scale from 1 (not felt) to 10 (very heavy damage), based on descriptions such as “felt indoors” (MMI = 3) to “felt by all, windows, dishes, glassware broken, weak plaster cracked” (MMI = 6) to “some structures with complete collapse” (MMI = 9). DYFI allows anyone to report their earthquake experience. There is no need for the citizen to have experience in seismology. This citizen reporting allows the USGS to continue to learn and understand more about earthquake shaking and effects. In addition, the USGS can then use these data to very rapidly map out the intensity of shaking in the affected region, which can help inform emergency managers, the media and the public in the immediate aftermath of an earthquake.

The vast amount of new data on earthquake ground motions and effects being collected from online citizen responses with the DYFI program offers a valuable new data resource for both qualitative and quantitative earthquake studies and has the potential to address some longstanding controversies in earthquake science.

Main Lessons

  • QA/QC: The website application filters out erroneous responses. Wald et al. (2011) note that the uncertainty of the intensity reported decreases when a higher number (>3) responses are obtained per location; more responses gives a more reliable average of the shaking over the area. The USGS reserve the right to manually exclude any responses they deem erroneous or unnaturally low or high given the magnitude of the earthquake and distance of the observers.
  • The input form is very easy to use and avoids use of seismology terminology.
  • Atkinson and Wald (2007) and Wald et al. (2011) indicate that the data collected from DYFI are very valuable. Their analyses of the DYFI data show this data as being extremely useful for rapid post-earthquake information and “they are also robust and of surprisingly high utility”. The data collected offers the potential to not only describe ground-motion effects qualitatively but to be used in quantitative scientific studies. Atkinson and Wald (2007) state that “the key to the usefulness of the data is simply this: they make up in quantity what they may lack in quality. Because there are so many responses, stable statistics on average effects are produced, illuminating ground-motion trends and allowing effective correlation and calibration with more-quantitative ground-motion measures”.

Reference Materials

Atkinson, G. M., and D. J. Wald (2007) “Did You Feel It?” intensity data: A surprisingly good measure of earthquake ground motion  Seism. Res. Lett. 78, 362-368

Wald, D.J., V. Quitoriano, C.B. Worden, M. Hopper, and J. W. Dewey (2011). USGS “Did You Feel It?” Internet-based Macroseismic Intensity Maps, Annals of Geophysics, 39 pp., 688-709.

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