Update: I have since confirmed that the time of the Chinese quake was 2:28pm (CST – Central China Time) and I felt the vibrations between 12:20am and 1:00am. Also since this writing the quake’s magnitude has been upgraded from 7.8 to 7.9 which is 1.41 times more powerful (Richter scale calculator available here). After the quake they immediately had a magnitude 6.0 aftershock and have had aftershocks ranging from 4.7 to 5.8 for a full 24 hours after the quake at intervals of 15 to 30 minutes. This quake released 31 times more energy than the 1989 San Francisco Earthquake which was a 6.9. Our thoughts are with Sichuan today.
Last night some time between 10pm and 12:30am I was lying in my parents in law’s living room in Elizabeth, Colorado flat on my back on the carpet. I had my head on the floor with my skull firmly on the ground – I had cycled hard that morning and was stretching my back out.
The living room floor is above the basement, so it’s a floor suspended above a TV room below it.
I felt a vibration as though some deep force shook the floor. It lasted about 0.5 to 1 seconds. It felt very clearly like something that had an external source – not someone jumping on the floor. It wasn’t a very strong vibration – it was slight but with a very very low frequency. You wouldn’t be able to hear it – I just felt it through the base of my skull that was resting on the floor.
Everyone in the house was downstairs watching TV and all were sitting down at the time on furniture on a concrete floor. So it couldn’t have been anyone in the house. The properties out here are each on 5 to 10 acres, so the houses are at least 1000 ft apart – so it couldn’t have been any neighbors. It’s also very rural and there weren’t any cars or trucks outside at that time of night.
The vibration was such a strange occurrence that when my wife walked upstairs a few minutes later I told her about it and mentioned that I wondered if we might have an earthquake.
This morning I read about the 7.8 magnitude quake in South Western China during the middle of their day. It occurred at the same time as my little skull vibration incident.
In 1996 a Northwestern University seismologist and a colleague working for the French Atomic Energy Commission proved that the Earth has a solid core. They did this using an earthquake in the Flores Sea in the South Pacific and analyzing the vibrations using a seismic array in France after they had traveled through the Earth.
The magnitude of the quake in the Flores Sea was 7.8 – exactly the same magnitude as the Chinese quake.
My guess is that I did feel the quake and that my parents suspended living room floor has a resonant frequency the same or similar to the quake vibrations when they arrived.