  MyShake is a free citizen science smartphone app that provides a range of
features related to earthquakes. Features available globally include rapid
post-earthquake notifications, live maps of earthquake damage as reported by
MyShake users, safety tips and various educational features. The app also uses
the accelerometer to detect earthquake shaking and to record and submit
waveforms to a central archive. In addition, MyShake delivers earthquake early
warning alerts in California, Oregon and Washington. In this study we compare
the felt shaking reports provided by MyShake users in California with the US
Geological Survey's "Did You Feel It?" intensity reports. The MyShake app
simply asks "What strength of shaking did you feel" and users report on a
five-level scale. When the reports are averaged in spatial bins, we find strong
correlations with the Modified Mercalli Intensity scale values reported by the
USGS based on the much more complex DYFI surveys. The MyShake felt reports can
therefore also be used to generate shaking intensity maps.
