1 Inflammation of the gingiva, bone loss, and increased gingival recession may progress slower than with other forms of periodontitis.  Periodontitis Associated with Systemic Diseases - Systemic diseases, such as heart disease, diabetes, and certain forms of arthritis, may have a correlation with periodontitis.
Along Faults. Earthquakes can also occur far from the edges of plates, along faults. Faults are cracks in the earth where sections of a plate (or two plates) are moving in different directions. Faults are caused by all that bumping and sliding the plates do. They are more common near the edges of the plates.
There are transform faults which the earth crust rubs past each other. Mid ocean ridges and rift valleys which divergence takes place, and deep ocean trenches where convergence takes place. The biggest earthquakes happen at subduction zones though. An earthquake is caused by a sudden slip on a fault.