Hi Jennifer,
Okay, a few questions.
What's the data frame using? NAD 1983 UTM 10N or 11N?
Did the definition query work?
What coordinate system is the earthquake layer in? NAD 1983 (a geographic coordinate system)?
What's the coordinate system of the buffer layer? I think it should be NAD 1983 (lat/lon).
What are the extents of the buffer layer? Please add it to a new data frame.
One possibility is that the buffer layer has a UTM coordinate system, but the actual coordinate values are in decimal degrees. That would lead to the buffer data being far to the south west of the other layers in the data frame (in UTM).
That's a good try, exporting the layer. Unfortunately, if the data's already not showing up, exporting while reprojecting it isn't going to help.
Melita