M3.4 near Hercules, CA
Map showing May 21 M 3.4 Hercules quake and aftershocks, and area fault zones (Click to view larger)
- Date & Time (Local): 2011/05/21 19:04:56(PDT)
- Date & Time (UTC): 2011/05/22 02:04:56 (UTC)
- Location: 2 miles SE of Hercules, CA
- Depth (km): 9.8
- Magnitude: 3.4 Mw
The CISN Northern California Management Center produces ShakeMaps for events of M3.5 and higher. ShakeMaps are based on the observed ground motions from seismic instruments combined with predicted motions in areas without sensors.
This earthquake was widely felt in the East Bay. People with Internet access can report their observations of shaking and damage through the Did You Feel It? Web site. Unlike the ShakeMaps - which are based on data from seismic instruments - these maps are based on human observations. You can contribute to these data by filling out the form for the event.