Earth Quake Info?

Question

I live about45 minuted to 1 hour away from Louisville (eastview Ky) and the earth quake did wake my husband and I up. I just can't fathem the power that they have to shake parts of land , homes and such like it is nothing.

My first question is this: for those who have been through this experience, does it still feel like a crazy dream to you? It's like I can't get over the fact that the earth was actually shaking and there was nothing in my power I could do to stop it. I guess in my life I like to be able to control my surroundings and this is one thing I had absolutly no control over. (It shook our house pretty hard; a pictures came off of the wall and our walls were making cracking noises... it was really scary!)

My second question is: what makes an earth quake? How does it work and what determines where they will be?

Answer 1

The scary part is not knowing how long the shaking will be or if the shaking will intensify.  I was in Calif during the Northridge quake of the 1990's.  The shaking woke everbody up from their sleep.  Unlike the S. Illinois quake, the Northridge quake got stronger after it passed the intensity level you experienced.  I suppose, if it is your 1st real temblor it may seem like a dream.  However, if you don't suffer any real property damage or injuries your experinece is mostly the level of water cooler talk.  Count your blessings.

Earth shaking is the result of the arrival of the P and S waves.  The P waves travel like a toy slinky that is stretched out on the floor.  They also travel faster and are less damagagin the the S waves.  The S waves travel like a rope attached to a wall with someone shaking it up and down.  They travel slower but are more powerful than P waves.  The time difference between their arrival is a measure of the distance the waves travel.  That is how a basic seismograph works.  Shaking is more pronounced on sedimentary and softer rocks, while on bedrock like granite, shaking is less.  That is why there was more damage in the San Fernando Valley than in the hills above it during the Northridge quake.

Most active earthquaqe zones are on the edge of tectonic plates.  The earthquakes in the Midwest are mostly likely caused be localized crustal deformation that is not directly related to plate tectonics.

Answer 2

Wow, I know what you mean! I felt the earthquake this morning too and I live in central Indiana. We almost never get earthquakes!