The shaded oval on the map is is the felt area of the largest after-shock. This after shock was used to pinpoint the likely location of the main shock, plus or minus 50 km. From the USGS's Earthquake Hazards web site  | 
Last updated: March 31, 2012
 
The shaded oval on the map is is the felt area of the largest after-shock. This after shock was used to pinpoint the likely location of the main shock, plus or minus 50 km. From the USGS's Earthquake Hazards web site  | 
Last updated: March 31, 2012