The Did You Feel It? (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. 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. Additionally, the scientists wanted to measure the accuracy and timeliness of the DYFI system data. Topics: Crowdsourcing, Data Collection, Earthquakes, Fault Lines, Internet, Mapping, Natural Disasters, Seismograph.