I grew up in southern California and have been through several earthquakes, including the magnitude 6.6 Northridge Earthquake in 1994. When I read about the North Korean nuclear-seismological debate, I wondered what it would feel like to be on top of an underground nuclear test.
To find out, I combined a Wikipedia chart of the Richter scale magnitudes of various earthquakes and explosions with a chart giving rough conversions between earthquake magnitudes on the Richter scale and their felt intensities on the Modified Mercali Scale. Here is the result.
|Event||Richter magnitude||TNT Equivalent||Intensity|
|WWII conventional bombs||1.5||178 kg (392 lb)||Detected only by seismographs|
|late WWII conventional bombs||2.0||1 metric ton||Detected only by seismographs|
|WWII blockbuster bomb||2.5||5.6 metric tons||Detected only by seismographs|
|Small atomic bomb||4.0||1 kiloton||Resembling vibrations caused by heavy traffic.|
|5.0||32 kiloton||Sleepers awakened and bells ring.|
|Little Skull Mtn, NV Quake, 1992||5.5||178 kilotons||Trees sway, some damage from overturning and falling objects.|
|Double Spring Flat, NV Quake, 1994||6.0||1 megaton||General alarm, cracking of walls.|
|Northridge quake, 1994||6.5||5.6 megatons||Chimneys fall and there is some damage to buildings.|
|Tsar Bomba, largest|
thermonuclear weapon ever tested
|~7.0||50 megatons||Ground badly cracked and many buildings are destroyed. There are some landslides.|
|Landers, CA Quake, 1992||7.5||178 megatons||Ground badly cracked and many buildings are destroyed. There are some landslides.|